Merge branch 'master' into for-next

Fast-forwarded to current state of Linus' tree as there are patches to be
applied for files that didn't exist on the old branch.

13 files changed, 2145 insertions, 1488 deletions

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index ba95cba192b..c6828b68d77 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -30,7 +30,7 @@
 
 /* We maintain a trivial check sum in our on disk activity log.
  * With that we can ensure correct operation even when the storage
- * device might do a partial (last) sector write while loosing power.
+ * device might do a partial (last) sector write while losing power.
  */
 struct __packed al_transaction {
 	u32       magic;
@@ -80,7 +80,7 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
 
 	if ((rw & WRITE) && !test_bit(MD_NO_FUA, &mdev->flags))
 		rw |= REQ_FUA;
-	rw |= REQ_UNPLUG | REQ_SYNC;
+	rw |= REQ_SYNC;
 
 	bio = bio_alloc(GFP_NOIO, 1);
 	bio->bi_bdev = bdev->md_bdev;
@@ -92,7 +92,7 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
 	bio->bi_end_io = drbd_md_io_complete;
 	bio->bi_rw = rw;
 
-	if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
+	if (drbd_insert_fault(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
 		bio_endio(bio, -EIO);
 	else
 		submit_bio(rw, bio);
@@ -176,13 +176,17 @@ static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
 	struct lc_element *al_ext;
 	struct lc_element *tmp;
 	unsigned long     al_flags = 0;
+	int wake;
 
 	spin_lock_irq(&mdev->al_lock);
 	tmp = lc_find(mdev->resync, enr/AL_EXT_PER_BM_SECT);
 	if (unlikely(tmp != NULL)) {
 		struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
 		if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
+			wake = !test_and_set_bit(BME_PRIORITY, &bm_ext->flags);
 			spin_unlock_irq(&mdev->al_lock);
+			if (wake)
+				wake_up(&mdev->al_wait);
 			return NULL;
 		}
 	}
@@ -258,6 +262,33 @@ void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector)
 	spin_unlock_irqrestore(&mdev->al_lock, flags);
 }
 
+#if (PAGE_SHIFT + 3) < (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT)
+/* Currently BM_BLOCK_SHIFT, BM_EXT_SHIFT and AL_EXTENT_SHIFT
+ * are still coupled, or assume too much about their relation.
+ * Code below will not work if this is violated.
+ * Will be cleaned up with some followup patch.
+ */
+# error FIXME
+#endif
+
+static unsigned int al_extent_to_bm_page(unsigned int al_enr)
+{
+	return al_enr >>
+		/* bit to page */
+		((PAGE_SHIFT + 3) -
+		/* al extent number to bit */
+		 (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT));
+}
+
+static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)
+{
+	return rs_enr >>
+		/* bit to page */
+		((PAGE_SHIFT + 3) -
+		/* al extent number to bit */
+		 (BM_EXT_SHIFT - BM_BLOCK_SHIFT));
+}
+
 int
 w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
 {
@@ -285,7 +316,7 @@ w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
 	 * For now, we must not write the transaction,
 	 * if we cannot write out the bitmap of the evicted extent. */
 	if (mdev->state.conn < C_CONNECTED && evicted != LC_FREE)
-		drbd_bm_write_sect(mdev, evicted/AL_EXT_PER_BM_SECT);
+		drbd_bm_write_page(mdev, al_extent_to_bm_page(evicted));
 
 	/* The bitmap write may have failed, causing a state change. */
 	if (mdev->state.disk < D_INCONSISTENT) {
@@ -334,7 +365,7 @@ w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
 		+ mdev->ldev->md.al_offset + mdev->al_tr_pos;
 
 	if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE))
-		drbd_chk_io_error(mdev, 1, TRUE);
+		drbd_chk_io_error(mdev, 1, true);
 
 	if (++mdev->al_tr_pos >
 	    div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
@@ -511,227 +542,6 @@ cancel:
 	return 1;
 }
 
-static void atodb_endio(struct bio *bio, int error)
-{
-	struct drbd_atodb_wait *wc = bio->bi_private;
-	struct drbd_conf *mdev = wc->mdev;
-	struct page *page;
-	int uptodate = bio_flagged(bio, BIO_UPTODATE);
-
-	/* strange behavior of some lower level drivers...
-	 * fail the request by clearing the uptodate flag,
-	 * but do not return any error?! */
-	if (!error && !uptodate)
-		error = -EIO;
-
-	drbd_chk_io_error(mdev, error, TRUE);
-	if (error && wc->error == 0)
-		wc->error = error;
-
-	if (atomic_dec_and_test(&wc->count))
-		complete(&wc->io_done);
-
-	page = bio->bi_io_vec[0].bv_page;
-	put_page(page);
-	bio_put(bio);
-	mdev->bm_writ_cnt++;
-	put_ldev(mdev);
-}
-
-/* sector to word */
-#define S2W(s)	((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
-
-/* activity log to on disk bitmap -- prepare bio unless that sector
- * is already covered by previously prepared bios */
-static int atodb_prepare_unless_covered(struct drbd_conf *mdev,
-					struct bio **bios,
-					unsigned int enr,
-					struct drbd_atodb_wait *wc) __must_hold(local)
-{
-	struct bio *bio;
-	struct page *page;
-	sector_t on_disk_sector;
-	unsigned int page_offset = PAGE_SIZE;
-	int offset;
-	int i = 0;
-	int err = -ENOMEM;
-
-	/* We always write aligned, full 4k blocks,
-	 * so we can ignore the logical_block_size (for now) */
-	enr &= ~7U;
-	on_disk_sector = enr + mdev->ldev->md.md_offset
-			     + mdev->ldev->md.bm_offset;
-
-	D_ASSERT(!(on_disk_sector & 7U));
-
-	/* Check if that enr is already covered by an already created bio.
-	 * Caution, bios[] is not NULL terminated,
-	 * but only initialized to all NULL.
-	 * For completely scattered activity log,
-	 * the last invocation iterates over all bios,
-	 * and finds the last NULL entry.
-	 */
-	while ((bio = bios[i])) {
-		if (bio->bi_sector == on_disk_sector)
-			return 0;
-		i++;
-	}
-	/* bios[i] == NULL, the next not yet used slot */
-
-	/* GFP_KERNEL, we are not in the write-out path */
-	bio = bio_alloc(GFP_KERNEL, 1);
-	if (bio == NULL)
-		return -ENOMEM;
-
-	if (i > 0) {
-		const struct bio_vec *prev_bv = bios[i-1]->bi_io_vec;
-		page_offset = prev_bv->bv_offset + prev_bv->bv_len;
-		page = prev_bv->bv_page;
-	}
-	if (page_offset == PAGE_SIZE) {
-		page = alloc_page(__GFP_HIGHMEM);
-		if (page == NULL)
-			goto out_bio_put;
-		page_offset = 0;
-	} else {
-		get_page(page);
-	}
-
-	offset = S2W(enr);
-	drbd_bm_get_lel(mdev, offset,
-			min_t(size_t, S2W(8), drbd_bm_words(mdev) - offset),
-			kmap(page) + page_offset);
-	kunmap(page);
-
-	bio->bi_private = wc;
-	bio->bi_end_io = atodb_endio;
-	bio->bi_bdev = mdev->ldev->md_bdev;
-	bio->bi_sector = on_disk_sector;
-
-	if (bio_add_page(bio, page, 4096, page_offset) != 4096)
-		goto out_put_page;
-
-	atomic_inc(&wc->count);
-	/* we already know that we may do this...
-	 * get_ldev_if_state(mdev,D_ATTACHING);
-	 * just get the extra reference, so that the local_cnt reflects
-	 * the number of pending IO requests DRBD at its backing device.
-	 */
-	atomic_inc(&mdev->local_cnt);
-
-	bios[i] = bio;
-
-	return 0;
-
-out_put_page:
-	err = -EINVAL;
-	put_page(page);
-out_bio_put:
-	bio_put(bio);
-	return err;
-}
-
-/**
- * drbd_al_to_on_disk_bm() -  * Writes bitmap parts covered by active AL extents
- * @mdev:	DRBD device.
- *
- * Called when we detach (unconfigure) local storage,
- * or when we go from R_PRIMARY to R_SECONDARY role.
- */
-void drbd_al_to_on_disk_bm(struct drbd_conf *mdev)
-{
-	int i, nr_elements;
-	unsigned int enr;
-	struct bio **bios;
-	struct drbd_atodb_wait wc;
-
-	ERR_IF (!get_ldev_if_state(mdev, D_ATTACHING))
-		return; /* sorry, I don't have any act_log etc... */
-
-	wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
-
-	nr_elements = mdev->act_log->nr_elements;
-
-	/* GFP_KERNEL, we are not in anyone's write-out path */
-	bios = kzalloc(sizeof(struct bio *) * nr_elements, GFP_KERNEL);
-	if (!bios)
-		goto submit_one_by_one;
-
-	atomic_set(&wc.count, 0);
-	init_completion(&wc.io_done);
-	wc.mdev = mdev;
-	wc.error = 0;
-
-	for (i = 0; i < nr_elements; i++) {
-		enr = lc_element_by_index(mdev->act_log, i)->lc_number;
-		if (enr == LC_FREE)
-			continue;
-		/* next statement also does atomic_inc wc.count and local_cnt */
-		if (atodb_prepare_unless_covered(mdev, bios,
-						enr/AL_EXT_PER_BM_SECT,
-						&wc))
-			goto free_bios_submit_one_by_one;
-	}
-
-	/* unnecessary optimization? */
-	lc_unlock(mdev->act_log);
-	wake_up(&mdev->al_wait);
-
-	/* all prepared, submit them */
-	for (i = 0; i < nr_elements; i++) {
-		if (bios[i] == NULL)
-			break;
-		if (FAULT_ACTIVE(mdev, DRBD_FAULT_MD_WR)) {
-			bios[i]->bi_rw = WRITE;
-			bio_endio(bios[i], -EIO);
-		} else {
-			submit_bio(WRITE, bios[i]);
-		}
-	}
-
-	drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
-
-	/* always (try to) flush bitmap to stable storage */
-	drbd_md_flush(mdev);
-
-	/* In case we did not submit a single IO do not wait for
-	 * them to complete. ( Because we would wait forever here. )
-	 *
-	 * In case we had IOs and they are already complete, there
-	 * is not point in waiting anyways.
-	 * Therefore this if () ... */
-	if (atomic_read(&wc.count))
-		wait_for_completion(&wc.io_done);
-
-	put_ldev(mdev);
-
-	kfree(bios);
-	return;
-
- free_bios_submit_one_by_one:
-	/* free everything by calling the endio callback directly. */
-	for (i = 0; i < nr_elements && bios[i]; i++)
-		bio_endio(bios[i], 0);
-
-	kfree(bios);
-
- submit_one_by_one:
-	dev_warn(DEV, "Using the slow drbd_al_to_on_disk_bm()\n");
-
-	for (i = 0; i < mdev->act_log->nr_elements; i++) {
-		enr = lc_element_by_index(mdev->act_log, i)->lc_number;
-		if (enr == LC_FREE)
-			continue;
-		/* Really slow: if we have al-extents 16..19 active,
-		 * sector 4 will be written four times! Synchronous! */
-		drbd_bm_write_sect(mdev, enr/AL_EXT_PER_BM_SECT);
-	}
-
-	lc_unlock(mdev->act_log);
-	wake_up(&mdev->al_wait);
-	put_ldev(mdev);
-}
-
 /**
  * drbd_al_apply_to_bm() - Sets the bitmap to diry(1) where covered ba active AL extents
  * @mdev:	DRBD device.
@@ -811,7 +621,7 @@ static int w_update_odbm(struct drbd_conf *mdev, struct drbd_work *w, int unused
 		return 1;
 	}
 
-	drbd_bm_write_sect(mdev, udw->enr);
+	drbd_bm_write_page(mdev, rs_extent_to_bm_page(udw->enr));
 	put_ldev(mdev);
 
 	kfree(udw);
@@ -891,7 +701,6 @@ static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector,
 				dev_warn(DEV, "Kicking resync_lru element enr=%u "
 				     "out with rs_failed=%d\n",
 				     ext->lce.lc_number, ext->rs_failed);
-				set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
 			}
 			ext->rs_left = rs_left;
 			ext->rs_failed = success ? 0 : count;
@@ -910,7 +719,6 @@ static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector,
 				drbd_queue_work_front(&mdev->data.work, &udw->w);
 			} else {
 				dev_warn(DEV, "Could not kmalloc an udw\n");
-				set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
 			}
 		}
 	} else {
@@ -921,6 +729,22 @@ static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector,
 	}
 }
 
+void drbd_advance_rs_marks(struct drbd_conf *mdev, unsigned long still_to_go)
+{
+	unsigned long now = jiffies;
+	unsigned long last = mdev->rs_mark_time[mdev->rs_last_mark];
+	int next = (mdev->rs_last_mark + 1) % DRBD_SYNC_MARKS;
+	if (time_after_eq(now, last + DRBD_SYNC_MARK_STEP)) {
+		if (mdev->rs_mark_left[mdev->rs_last_mark] != still_to_go &&
+		    mdev->state.conn != C_PAUSED_SYNC_T &&
+		    mdev->state.conn != C_PAUSED_SYNC_S) {
+			mdev->rs_mark_time[next] = now;
+			mdev->rs_mark_left[next] = still_to_go;
+			mdev->rs_last_mark = next;
+		}
+	}
+}
+
 /* clear the bit corresponding to the piece of storage in question:
  * size byte of data starting from sector.  Only clear a bits of the affected
  * one ore more _aligned_ BM_BLOCK_SIZE blocks.
@@ -938,7 +762,7 @@ void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector, int size,
 	int wake_up = 0;
 	unsigned long flags;
 
-	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_BIO_SIZE) {
 		dev_err(DEV, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
 				(unsigned long long)sector, size);
 		return;
@@ -971,21 +795,9 @@ void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector, int size,
 	 */
 	count = drbd_bm_clear_bits(mdev, sbnr, ebnr);
 	if (count && get_ldev(mdev)) {
-		unsigned long now = jiffies;
-		unsigned long last = mdev->rs_mark_time[mdev->rs_last_mark];
-		int next = (mdev->rs_last_mark + 1) % DRBD_SYNC_MARKS;
-		if (time_after_eq(now, last + DRBD_SYNC_MARK_STEP)) {
-			unsigned long tw = drbd_bm_total_weight(mdev);
-			if (mdev->rs_mark_left[mdev->rs_last_mark] != tw &&
-			    mdev->state.conn != C_PAUSED_SYNC_T &&
-			    mdev->state.conn != C_PAUSED_SYNC_S) {
-				mdev->rs_mark_time[next] = now;
-				mdev->rs_mark_left[next] = tw;
-				mdev->rs_last_mark = next;
-			}
-		}
+		drbd_advance_rs_marks(mdev, drbd_bm_total_weight(mdev));
 		spin_lock_irqsave(&mdev->al_lock, flags);
-		drbd_try_clear_on_disk_bm(mdev, sector, count, TRUE);
+		drbd_try_clear_on_disk_bm(mdev, sector, count, true);
 		spin_unlock_irqrestore(&mdev->al_lock, flags);
 
 		/* just wake_up unconditional now, various lc_chaged(),
@@ -1000,27 +812,27 @@ void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector, int size,
 /*
  * this is intended to set one request worth of data out of sync.
  * affects at least 1 bit,
- * and at most 1+DRBD_MAX_SEGMENT_SIZE/BM_BLOCK_SIZE bits.
+ * and at most 1+DRBD_MAX_BIO_SIZE/BM_BLOCK_SIZE bits.
  *
  * called by tl_clear and drbd_send_dblock (==drbd_make_request).
  * so this can be _any_ process.
  */
-void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector, int size,
+int __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector, int size,
 			    const char *file, const unsigned int line)
 {
 	unsigned long sbnr, ebnr, lbnr, flags;
 	sector_t esector, nr_sectors;
-	unsigned int enr, count;
+	unsigned int enr, count = 0;
 	struct lc_element *e;
 
-	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_BIO_SIZE) {
 		dev_err(DEV, "sector: %llus, size: %d\n",
 			(unsigned long long)sector, size);
-		return;
+		return 0;
 	}
 
 	if (!get_ldev(mdev))
-		return; /* no disk, no metadata, no bitmap to set bits in */
+		return 0; /* no disk, no metadata, no bitmap to set bits in */
 
 	nr_sectors = drbd_get_capacity(mdev->this_bdev);
 	esector = sector + (size >> 9) - 1;
@@ -1050,6 +862,8 @@ void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector, int size,
 
 out:
 	put_ldev(mdev);
+
+	return count;
 }
 
 static
@@ -1130,7 +944,10 @@ int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
 	unsigned int enr = BM_SECT_TO_EXT(sector);
 	struct bm_extent *bm_ext;
 	int i, sig;
+	int sa = 200; /* Step aside 200 times, then grab the extent and let app-IO wait.
+			 200 times -> 20 seconds. */
 
+retry:
 	sig = wait_event_interruptible(mdev->al_wait,
 			(bm_ext = _bme_get(mdev, enr)));
 	if (sig)
@@ -1141,16 +958,25 @@ int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
 
 	for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
 		sig = wait_event_interruptible(mdev->al_wait,
-				!_is_in_al(mdev, enr * AL_EXT_PER_BM_SECT + i));
-		if (sig) {
+					       !_is_in_al(mdev, enr * AL_EXT_PER_BM_SECT + i) ||
+					       test_bit(BME_PRIORITY, &bm_ext->flags));
+
+		if (sig || (test_bit(BME_PRIORITY, &bm_ext->flags) && sa)) {
 			spin_lock_irq(&mdev->al_lock);
 			if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
-				clear_bit(BME_NO_WRITES, &bm_ext->flags);
+				bm_ext->flags = 0; /* clears BME_NO_WRITES and eventually BME_PRIORITY */
 				mdev->resync_locked--;
 				wake_up(&mdev->al_wait);
 			}
 			spin_unlock_irq(&mdev->al_lock);
-			return -EINTR;
+			if (sig)
+				return -EINTR;
+			if (schedule_timeout_interruptible(HZ/10))
+				return -EINTR;
+			if (sa && --sa == 0)
+				dev_warn(DEV,"drbd_rs_begin_io() stepped aside for 20sec."
+					 "Resync stalled?\n");
+			goto retry;
 		}
 	}
 	set_bit(BME_LOCKED, &bm_ext->flags);
@@ -1293,8 +1119,7 @@ void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector)
 	}
 
 	if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
-		clear_bit(BME_LOCKED, &bm_ext->flags);
-		clear_bit(BME_NO_WRITES, &bm_ext->flags);
+		bm_ext->flags = 0; /* clear BME_LOCKED, BME_NO_WRITES and BME_PRIORITY */
 		mdev->resync_locked--;
 		wake_up(&mdev->al_wait);
 	}
@@ -1385,7 +1210,7 @@ void drbd_rs_failed_io(struct drbd_conf *mdev, sector_t sector, int size)
 	sector_t esector, nr_sectors;
 	int wake_up = 0;
 
-	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_BIO_SIZE) {
 		dev_err(DEV, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
 				(unsigned long long)sector, size);
 		return;
@@ -1422,7 +1247,7 @@ void drbd_rs_failed_io(struct drbd_conf *mdev, sector_t sector, int size)
 		mdev->rs_failed += count;
 
 		if (get_ldev(mdev)) {
-			drbd_try_clear_on_disk_bm(mdev, sector, count, FALSE);
+			drbd_try_clear_on_disk_bm(mdev, sector, count, false);
 			put_ldev(mdev);
 		}
 
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index fd42832f785..76210ba401a 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -28,18 +28,56 @@
 #include <linux/drbd.h>
 #include <linux/slab.h>
 #include <asm/kmap_types.h>
+
 #include "drbd_int.h"
 
+
 /* OPAQUE outside this file!
  * interface defined in drbd_int.h
 
  * convention:
  * function name drbd_bm_... => used elsewhere, "public".
  * function name      bm_... => internal to implementation, "private".
+ */
 
- * Note that since find_first_bit returns int, at the current granularity of
- * the bitmap (4KB per byte), this implementation "only" supports up to
- * 1<<(32+12) == 16 TB...
+
+/*
+ * LIMITATIONS:
+ * We want to support >= peta byte of backend storage, while for now still using
+ * a granularity of one bit per 4KiB of storage.
+ * 1 << 50		bytes backend storage (1 PiB)
+ * 1 << (50 - 12)	bits needed
+ *	38 --> we need u64 to index and count bits
+ * 1 << (38 - 3)	bitmap bytes needed
+ *	35 --> we still need u64 to index and count bytes
+ *			(that's 32 GiB of bitmap for 1 PiB storage)
+ * 1 << (35 - 2)	32bit longs needed
+ *	33 --> we'd even need u64 to index and count 32bit long words.
+ * 1 << (35 - 3)	64bit longs needed
+ *	32 --> we could get away with a 32bit unsigned int to index and count
+ *	64bit long words, but I rather stay with unsigned long for now.
+ *	We probably should neither count nor point to bytes or long words
+ *	directly, but either by bitnumber, or by page index and offset.
+ * 1 << (35 - 12)
+ *	22 --> we need that much 4KiB pages of bitmap.
+ *	1 << (22 + 3) --> on a 64bit arch,
+ *	we need 32 MiB to store the array of page pointers.
+ *
+ * Because I'm lazy, and because the resulting patch was too large, too ugly
+ * and still incomplete, on 32bit we still "only" support 16 TiB (minus some),
+ * (1 << 32) bits * 4k storage.
+ *
+
+ * bitmap storage and IO:
+ *	Bitmap is stored little endian on disk, and is kept little endian in
+ *	core memory. Currently we still hold the full bitmap in core as long
+ *	as we are "attached" to a local disk, which at 32 GiB for 1PiB storage
+ *	seems excessive.
+ *
+ *	We plan to reduce the amount of in-core bitmap pages by pageing them in
+ *	and out against their on-disk location as necessary, but need to make
+ *	sure we don't cause too much meta data IO, and must not deadlock in
+ *	tight memory situations. This needs some more work.
  */
 
 /*
@@ -55,13 +93,9 @@
 struct drbd_bitmap {
 	struct page **bm_pages;
 	spinlock_t bm_lock;
-	/* WARNING unsigned long bm_*:
-	 * 32bit number of bit offset is just enough for 512 MB bitmap.
-	 * it will blow up if we make the bitmap bigger...
-	 * not that it makes much sense to have a bitmap that large,
-	 * rather change the granularity to 16k or 64k or something.
-	 * (that implies other problems, however...)
-	 */
+
+	/* see LIMITATIONS: above */
+
 	unsigned long bm_set;       /* nr of set bits; THINK maybe atomic_t? */
 	unsigned long bm_bits;
 	size_t   bm_words;
@@ -69,29 +103,18 @@ struct drbd_bitmap {
 	sector_t bm_dev_capacity;
 	struct mutex bm_change; /* serializes resize operations */
 
-	atomic_t bm_async_io;
-	wait_queue_head_t bm_io_wait;
+	wait_queue_head_t bm_io_wait; /* used to serialize IO of single pages */
 
-	unsigned long  bm_flags;
+	enum bm_flag bm_flags;
 
 	/* debugging aid, in case we are still racy somewhere */
 	char          *bm_why;
 	struct task_struct *bm_task;
 };
 
-/* definition of bits in bm_flags */
-#define BM_LOCKED       0
-#define BM_MD_IO_ERROR  1
-#define BM_P_VMALLOCED  2
-
 static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
 			       unsigned long e, int val, const enum km_type km);
 
-static int bm_is_locked(struct drbd_bitmap *b)
-{
-	return test_bit(BM_LOCKED, &b->bm_flags);
-}
-
 #define bm_print_lock_info(m) __bm_print_lock_info(m, __func__)
 static void __bm_print_lock_info(struct drbd_conf *mdev, const char *func)
 {
@@ -108,7 +131,7 @@ static void __bm_print_lock_info(struct drbd_conf *mdev, const char *func)
 	    b->bm_task == mdev->worker.task   ? "worker"   : "?");
 }
 
-void drbd_bm_lock(struct drbd_conf *mdev, char *why)
+void drbd_bm_lock(struct drbd_conf *mdev, char *why, enum bm_flag flags)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
 	int trylock_failed;
@@ -131,8 +154,9 @@ void drbd_bm_lock(struct drbd_conf *mdev, char *why)
 		    b->bm_task == mdev->worker.task   ? "worker"   : "?");
 		mutex_lock(&b->bm_change);
 	}
-	if (__test_and_set_bit(BM_LOCKED, &b->bm_flags))
+	if (BM_LOCKED_MASK & b->bm_flags)
 		dev_err(DEV, "FIXME bitmap already locked in bm_lock\n");
+	b->bm_flags |= flags & BM_LOCKED_MASK;
 
 	b->bm_why  = why;
 	b->bm_task = current;
@@ -146,31 +170,137 @@ void drbd_bm_unlock(struct drbd_conf *mdev)
 		return;
 	}
 
-	if (!__test_and_clear_bit(BM_LOCKED, &mdev->bitmap->bm_flags))
+	if (!(BM_LOCKED_MASK & mdev->bitmap->bm_flags))
 		dev_err(DEV, "FIXME bitmap not locked in bm_unlock\n");
 
+	b->bm_flags &= ~BM_LOCKED_MASK;
 	b->bm_why  = NULL;
 	b->bm_task = NULL;
 	mutex_unlock(&b->bm_change);
 }
 
-/* word offset to long pointer */
-static unsigned long *__bm_map_paddr(struct drbd_bitmap *b, unsigned long offset, const enum km_type km)
+/* we store some "meta" info about our pages in page->private */
+/* at a granularity of 4k storage per bitmap bit:
+ * one peta byte storage: 1<<50 byte, 1<<38 * 4k storage blocks
+ *  1<<38 bits,
+ *  1<<23 4k bitmap pages.
+ * Use 24 bits as page index, covers 2 peta byte storage
+ * at a granularity of 4k per bit.
+ * Used to report the failed page idx on io error from the endio handlers.
+ */
+#define BM_PAGE_IDX_MASK	((1UL<<24)-1)
+/* this page is currently read in, or written back */
+#define BM_PAGE_IO_LOCK		31
+/* if there has been an IO error for this page */
+#define BM_PAGE_IO_ERROR	30
+/* this is to be able to intelligently skip disk IO,
+ * set if bits have been set since last IO. */
+#define BM_PAGE_NEED_WRITEOUT	29
+/* to mark for lazy writeout once syncer cleared all clearable bits,
+ * we if bits have been cleared since last IO. */
+#define BM_PAGE_LAZY_WRITEOUT	28
+
+/* store_page_idx uses non-atomic assingment. It is only used directly after
+ * allocating the page.  All other bm_set_page_* and bm_clear_page_* need to
+ * use atomic bit manipulation, as set_out_of_sync (and therefore bitmap
+ * changes) may happen from various contexts, and wait_on_bit/wake_up_bit
+ * requires it all to be atomic as well. */
+static void bm_store_page_idx(struct page *page, unsigned long idx)
+{
+	BUG_ON(0 != (idx & ~BM_PAGE_IDX_MASK));
+	page_private(page) |= idx;
+}
+
+static unsigned long bm_page_to_idx(struct page *page)
 {
-	struct page *page;
-	unsigned long page_nr;
+	return page_private(page) & BM_PAGE_IDX_MASK;
+}
+
+/* As is very unlikely that the same page is under IO from more than one
+ * context, we can get away with a bit per page and one wait queue per bitmap.
+ */
+static void bm_page_lock_io(struct drbd_conf *mdev, int page_nr)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	void *addr = &page_private(b->bm_pages[page_nr]);
+	wait_event(b->bm_io_wait, !test_and_set_bit(BM_PAGE_IO_LOCK, addr));
+}
+
+static void bm_page_unlock_io(struct drbd_conf *mdev, int page_nr)
+{
+	struct drbd_bitmap *b = mdev->bitmap;
+	void *addr = &page_private(b->bm_pages[page_nr]);
+	clear_bit(BM_PAGE_IO_LOCK, addr);
+	smp_mb__after_clear_bit();
+	wake_up(&mdev->bitmap->bm_io_wait);
+}
+
+/* set _before_ submit_io, so it may be reset due to being changed
+ * while this page is in flight... will get submitted later again */
+static void bm_set_page_unchanged(struct page *page)
+{
+	/* use cmpxchg? */
+	clear_bit(BM_PAGE_NEED_WRITEOUT, &page_private(page));
+	clear_bit(BM_PAGE_LAZY_WRITEOUT, &page_private(page));
+}
 
+static void bm_set_page_need_writeout(struct page *page)
+{
+	set_bit(BM_PAGE_NEED_WRITEOUT, &page_private(page));
+}
+
+static int bm_test_page_unchanged(struct page *page)
+{
+	volatile const unsigned long *addr = &page_private(page);
+	return (*addr & ((1UL<<BM_PAGE_NEED_WRITEOUT)|(1UL<<BM_PAGE_LAZY_WRITEOUT))) == 0;
+}
+
+static void bm_set_page_io_err(struct page *page)
+{
+	set_bit(BM_PAGE_IO_ERROR, &page_private(page));
+}
+
+static void bm_clear_page_io_err(struct page *page)
+{
+	clear_bit(BM_PAGE_IO_ERROR, &page_private(page));
+}
+
+static void bm_set_page_lazy_writeout(struct page *page)
+{
+	set_bit(BM_PAGE_LAZY_WRITEOUT, &page_private(page));
+}
+
+static int bm_test_page_lazy_writeout(struct page *page)
+{
+	return test_bit(BM_PAGE_LAZY_WRITEOUT, &page_private(page));
+}
+
+/* on a 32bit box, this would allow for exactly (2<<38) bits. */
+static unsigned int bm_word_to_page_idx(struct drbd_bitmap *b, unsigned long long_nr)
+{
 	/* page_nr = (word*sizeof(long)) >> PAGE_SHIFT; */
-	page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+	unsigned int page_nr = long_nr >> (PAGE_SHIFT - LN2_BPL + 3);
 	BUG_ON(page_nr >= b->bm_number_of_pages);
-	page = b->bm_pages[page_nr];
+	return page_nr;
+}
 
+static unsigned int bm_bit_to_page_idx(struct drbd_bitmap *b, u64 bitnr)
+{
+	/* page_nr = (bitnr/8) >> PAGE_SHIFT; */
+	unsigned int page_nr = bitnr >> (PAGE_SHIFT + 3);
+	BUG_ON(page_nr >= b->bm_number_of_pages);
+	return page_nr;
+}
+
+static unsigned long *__bm_map_pidx(struct drbd_bitmap *b, unsigned int idx, const enum km_type km)
+{
+	struct page *page = b->bm_pages[idx];
 	return (unsigned long *) kmap_atomic(page, km);
 }
 
-static unsigned long * bm_map_paddr(struct drbd_bitmap *b, unsigned long offset)
+static unsigned long *bm_map_pidx(struct drbd_bitmap *b, unsigned int idx)
 {
-	return __bm_map_paddr(b, offset, KM_IRQ1);
+	return __bm_map_pidx(b, idx, KM_IRQ1);
 }
 
 static void __bm_unmap(unsigned long *p_addr, const enum km_type km)
@@ -202,6 +332,7 @@ static void bm_unmap(unsigned long *p_addr)
  * to be able to report device specific.
  */
 
+
 static void bm_free_pages(struct page **pages, unsigned long number)
 {
 	unsigned long i;
@@ -269,6 +400,9 @@ static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want)
 				bm_vk_free(new_pages, vmalloced);
 				return NULL;
 			}
+			/* we want to know which page it is
+			 * from the endio handlers */
+			bm_store_page_idx(page, i);
 			new_pages[i] = page;
 		}
 	} else {
@@ -280,9 +414,9 @@ static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want)
 	}
 
 	if (vmalloced)
-		set_bit(BM_P_VMALLOCED, &b->bm_flags);
+		b->bm_flags |= BM_P_VMALLOCED;
 	else
-		clear_bit(BM_P_VMALLOCED, &b->bm_flags);
+		b->bm_flags &= ~BM_P_VMALLOCED;
 
 	return new_pages;
 }
@@ -319,7 +453,7 @@ void drbd_bm_cleanup(struct drbd_conf *mdev)
 {
 	ERR_IF (!mdev->bitmap) return;
 	bm_free_pages(mdev->bitmap->bm_pages, mdev->bitmap->bm_number_of_pages);
-	bm_vk_free(mdev->bitmap->bm_pages, test_bit(BM_P_VMALLOCED, &mdev->bitmap->bm_flags));
+	bm_vk_free(mdev->bitmap->bm_pages, (BM_P_VMALLOCED & mdev->bitmap->bm_flags));
 	kfree(mdev->bitmap);
 	mdev->bitmap = NULL;
 }
@@ -329,22 +463,39 @@ void drbd_bm_cleanup(struct drbd_conf *mdev)
  * this masks out the remaining bits.
  * Returns the number of bits cleared.
  */
+#define BITS_PER_PAGE		(1UL << (PAGE_SHIFT + 3))
+#define BITS_PER_PAGE_MASK	(BITS_PER_PAGE - 1)
+#define BITS_PER_LONG_MASK	(BITS_PER_LONG - 1)
 static int bm_clear_surplus(struct drbd_bitmap *b)
 {
-	const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
-	size_t w = b->bm_bits >> LN2_BPL;
-	int cleared = 0;
+	unsigned long mask;
 	unsigned long *p_addr, *bm;
+	int tmp;
+	int cleared = 0;
 
-	p_addr = bm_map_paddr(b, w);
-	bm = p_addr + MLPP(w);
-	if (w < b->bm_words) {
+	/* number of bits modulo bits per page */
+	tmp = (b->bm_bits & BITS_PER_PAGE_MASK);
+	/* mask the used bits of the word containing the last bit */
+	mask = (1UL << (tmp & BITS_PER_LONG_MASK)) -1;
+	/* bitmap is always stored little endian,
+	 * on disk and in core memory alike */
+	mask = cpu_to_lel(mask);
+
+	p_addr = bm_map_pidx(b, b->bm_number_of_pages - 1);
+	bm = p_addr + (tmp/BITS_PER_LONG);
+	if (mask) {
+		/* If mask != 0, we are not exactly aligned, so bm now points
+		 * to the long containing the last bit.
+		 * If mask == 0, bm already points to the word immediately
+		 * after the last (long word aligned) bit. */
 		cleared = hweight_long(*bm & ~mask);
 		*bm &= mask;
-		w++; bm++;
+		bm++;
 	}
 
-	if (w < b->bm_words) {
+	if (BITS_PER_LONG == 32 && ((bm - p_addr) & 1) == 1) {
+		/* on a 32bit arch, we may need to zero out
+		 * a padding long to align with a 64bit remote */
 		cleared += hweight_long(*bm);
 		*bm = 0;
 	}
@@ -354,66 +505,75 @@ static int bm_clear_surplus(struct drbd_bitmap *b)
 
 static void bm_set_surplus(struct drbd_bitmap *b)
 {
-	const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
-	size_t w = b->bm_bits >> LN2_BPL;
+	unsigned long mask;
 	unsigned long *p_addr, *bm;
-
-	p_addr = bm_map_paddr(b, w);
-	bm = p_addr + MLPP(w);
-	if (w < b->bm_words) {
+	int tmp;
+
+	/* number of bits modulo bits per page */
+	tmp = (b->bm_bits & BITS_PER_PAGE_MASK);
+	/* mask the used bits of the word containing the last bit */
+	mask = (1UL << (tmp & BITS_PER_LONG_MASK)) -1;
+	/* bitmap is always stored little endian,
+	 * on disk and in core memory alike */
+	mask = cpu_to_lel(mask);
+
+	p_addr = bm_map_pidx(b, b->bm_number_of_pages - 1);
+	bm = p_addr + (tmp/BITS_PER_LONG);
+	if (mask) {
+		/* If mask != 0, we are not exactly aligned, so bm now points
+		 * to the long containing the last bit.
+		 * If mask == 0, bm already points to the word immediately
+		 * after the last (long word aligned) bit. */
 		*bm |= ~mask;
-		bm++; w++;
+		bm++;
 	}
 
-	if (w < b->bm_words) {
-		*bm = ~(0UL);
+	if (BITS_PER_LONG == 32 && ((bm - p_addr) & 1) == 1) {
+		/* on a 32bit arch, we may need to zero out
+		 * a padding long to align with a 64bit remote */
+		*bm = ~0UL;
 	}
 	bm_unmap(p_addr);
 }
 
-static unsigned long __bm_count_bits(struct drbd_bitmap *b, const int swap_endian)
+/* you better not modify the bitmap while this is running,
+ * or its results will be stale */
+static unsigned long bm_count_bits(struct drbd_bitmap *b)
 {
-	unsigned long *p_addr, *bm, offset = 0;
+	unsigned long *p_addr;
 	unsigned long bits = 0;
-	unsigned long i, do_now;
-
-	while (offset < b->bm_words) {
-		i = do_now = min_t(size_t, b->bm_words-offset, LWPP);
-		p_addr = __bm_map_paddr(b, offset, KM_USER0);
-		bm = p_addr + MLPP(offset);
-		while (i--) {
-#ifndef __LITTLE_ENDIAN
-			if (swap_endian)
-				*bm = lel_to_cpu(*bm);
-#endif
-			bits += hweight_long(*bm++);
-		}
+	unsigned long mask = (1UL << (b->bm_bits & BITS_PER_LONG_MASK)) -1;
+	int idx, i, last_word;
+
+	/* all but last page */
+	for (idx = 0; idx < b->bm_number_of_pages - 1; idx++) {
+		p_addr = __bm_map_pidx(b, idx, KM_USER0);
+		for (i = 0; i < LWPP; i++)
+			bits += hweight_long(p_addr[i]);
 		__bm_unmap(p_addr, KM_USER0);
-		offset += do_now;
 		cond_resched();
 	}
-
+	/* last (or only) page */
+	last_word = ((b->bm_bits - 1) & BITS_PER_PAGE_MASK) >> LN2_BPL;
+	p_addr = __bm_map_pidx(b, idx, KM_USER0);
+	for (i = 0; i < last_word; i++)
+		bits += hweight_long(p_addr[i]);
+	p_addr[last_word] &= cpu_to_lel(mask);
+	bits += hweight_long(p_addr[last_word]);
+	/* 32bit arch, may have an unused padding long */
+	if (BITS_PER_LONG == 32 && (last_word & 1) == 0)
+		p_addr[last_word+1] = 0;
+	__bm_unmap(p_addr, KM_USER0);
 	return bits;
 }
 
-static unsigned long bm_count_bits(struct drbd_bitmap *b)
-{
-	return __bm_count_bits(b, 0);
-}
-
-static unsigned long bm_count_bits_swap_endian(struct drbd_bitmap *b)
-{
-	return __bm_count_bits(b, 1);
-}
-
 /* offset and len in long words.*/
 static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
 {
 	unsigned long *p_addr, *bm;
+	unsigned int idx;
 	size_t do_now, end;
 
-#define BM_SECTORS_PER_BIT (BM_BLOCK_SIZE/512)
-
 	end = offset + len;
 
 	if (end > b->bm_words) {
@@ -423,15 +583,16 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
 
 	while (offset < end) {
 		do_now = min_t(size_t, ALIGN(offset + 1, LWPP), end) - offset;
-		p_addr = bm_map_paddr(b, offset);
+		idx = bm_word_to_page_idx(b, offset);
+		p_addr = bm_map_pidx(b, idx);
 		bm = p_addr + MLPP(offset);
 		if (bm+do_now > p_addr + LWPP) {
 			printk(KERN_ALERT "drbd: BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
 			       p_addr, bm, (int)do_now);
-			break; /* breaks to after catch_oob_access_end() only! */
-		}
-		memset(bm, c, do_now * sizeof(long));
+		} else
+			memset(bm, c, do_now * sizeof(long));
 		bm_unmap(p_addr);
+		bm_set_page_need_writeout(b->bm_pages[idx]);
 		offset += do_now;
 	}
 }
@@ -447,7 +608,7 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
 int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
-	unsigned long bits, words, owords, obits, *p_addr, *bm;
+	unsigned long bits, words, owords, obits;
 	unsigned long want, have, onpages; /* number of pages */
 	struct page **npages, **opages = NULL;
 	int err = 0, growing;
@@ -455,7 +616,7 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 
 	ERR_IF(!b) return -ENOMEM;
 
-	drbd_bm_lock(mdev, "resize");
+	drbd_bm_lock(mdev, "resize", BM_LOCKED_MASK);
 
 	dev_info(DEV, "drbd_bm_resize called with capacity == %llu\n",
 			(unsigned long long)capacity);
@@ -463,7 +624,7 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 	if (capacity == b->bm_dev_capacity)
 		goto out;
 
-	opages_vmalloced = test_bit(BM_P_VMALLOCED, &b->bm_flags);
+	opages_vmalloced = (BM_P_VMALLOCED & b->bm_flags);
 
 	if (capacity == 0) {
 		spin_lock_irq(&b->bm_lock);
@@ -491,18 +652,23 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 	words = ALIGN(bits, 64) >> LN2_BPL;
 
 	if (get_ldev(mdev)) {
-		D_ASSERT((u64)bits <= (((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12));
+		u64 bits_on_disk = ((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12;
 		put_ldev(mdev);
+		if (bits > bits_on_disk) {
+			dev_info(DEV, "bits = %lu\n", bits);
+			dev_info(DEV, "bits_on_disk = %llu\n", bits_on_disk);
+			err = -ENOSPC;
+			goto out;
+		}
 	}
 
-	/* one extra long to catch off by one errors */
-	want = ALIGN((words+1)*sizeof(long), PAGE_SIZE) >> PAGE_SHIFT;
+	want = ALIGN(words*sizeof(long), PAGE_SIZE) >> PAGE_SHIFT;
 	have = b->bm_number_of_pages;
 	if (want == have) {
 		D_ASSERT(b->bm_pages != NULL);
 		npages = b->bm_pages;
 	} else {
-		if (FAULT_ACTIVE(mdev, DRBD_FAULT_BM_ALLOC))
+		if (drbd_insert_fault(mdev, DRBD_FAULT_BM_ALLOC))
 			npages = NULL;
 		else
 			npages = bm_realloc_pages(b, want);
@@ -542,11 +708,6 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 		bm_free_pages(opages + want, have - want);
 	}
 
-	p_addr = bm_map_paddr(b, words);
-	bm = p_addr + MLPP(words);
-	*bm = DRBD_MAGIC;
-	bm_unmap(p_addr);
-
 	(void)bm_clear_surplus(b);
 
 	spin_unlock_irq(&b->bm_lock);
@@ -554,7 +715,7 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 		bm_vk_free(opages, opages_vmalloced);
 	if (!growing)
 		b->bm_set = bm_count_bits(b);
-	dev_info(DEV, "resync bitmap: bits=%lu words=%lu\n", bits, words);
+	dev_info(DEV, "resync bitmap: bits=%lu words=%lu pages=%lu\n", bits, words, want);
 
  out:
 	drbd_bm_unlock(mdev);
@@ -624,6 +785,7 @@ void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset, size_t number,
 	struct drbd_bitmap *b = mdev->bitmap;
 	unsigned long *p_addr, *bm;
 	unsigned long word, bits;
+	unsigned int idx;
 	size_t end, do_now;
 
 	end = offset + number;
@@ -638,16 +800,18 @@ void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset, size_t number,
 	spin_lock_irq(&b->bm_lock);
 	while (offset < end) {
 		do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
-		p_addr = bm_map_paddr(b, offset);
+		idx = bm_word_to_page_idx(b, offset);
+		p_addr = bm_map_pidx(b, idx);
 		bm = p_addr + MLPP(offset);
 		offset += do_now;
 		while (do_now--) {
 			bits = hweight_long(*bm);
-			word = *bm | lel_to_cpu(*buffer++);
+			word = *bm | *buffer++;
 			*bm++ = word;
 			b->bm_set += hweight_long(word) - bits;
 		}
 		bm_unmap(p_addr);
+		bm_set_page_need_writeout(b->bm_pages[idx]);
 	}
 	/* with 32bit <-> 64bit cross-platform connect
 	 * this is only correct for current usage,
@@ -656,7 +820,6 @@ void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset, size_t number,
 	 */
 	if (end == b->bm_words)
 		b->bm_set -= bm_clear_surplus(b);
-
 	spin_unlock_irq(&b->bm_lock);
 }
 
@@ -686,11 +849,11 @@ void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset, size_t number,
 	else {
 		while (offset < end) {
 			do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
-			p_addr = bm_map_paddr(b, offset);
+			p_addr = bm_map_pidx(b, bm_word_to_page_idx(b, offset));
 			bm = p_addr + MLPP(offset);
 			offset += do_now;
 			while (do_now--)
-				*buffer++ = cpu_to_lel(*bm++);
+				*buffer++ = *bm++;
 			bm_unmap(p_addr);
 		}
 	}
@@ -724,9 +887,22 @@ void drbd_bm_clear_all(struct drbd_conf *mdev)
 	spin_unlock_irq(&b->bm_lock);
 }
 
+struct bm_aio_ctx {
+	struct drbd_conf *mdev;
+	atomic_t in_flight;
+	struct completion done;
+	unsigned flags;
+#define BM_AIO_COPY_PAGES	1
+	int error;
+};
+
+/* bv_page may be a copy, or may be the original */
 static void bm_async_io_complete(struct bio *bio, int error)
 {
-	struct drbd_bitmap *b = bio->bi_private;
+	struct bm_aio_ctx *ctx = bio->bi_private;
+	struct drbd_conf *mdev = ctx->mdev;
+	struct drbd_bitmap *b = mdev->bitmap;
+	unsigned int idx = bm_page_to_idx(bio->bi_io_vec[0].bv_page);
 	int uptodate = bio_flagged(bio, BIO_UPTODATE);
 
 
@@ -737,38 +913,83 @@ static void bm_async_io_complete(struct bio *bio, int error)
 	if (!error && !uptodate)
 		error = -EIO;
 
+	if ((ctx->flags & BM_AIO_COPY_PAGES) == 0 &&
+	    !bm_test_page_unchanged(b->bm_pages[idx]))
+		dev_warn(DEV, "bitmap page idx %u changed during IO!\n", idx);
+
 	if (error) {
-		/* doh. what now?
-		 * for now, set all bits, and flag MD_IO_ERROR */
-		__set_bit(BM_MD_IO_ERROR, &b->bm_flags);
+		/* ctx error will hold the completed-last non-zero error code,
+		 * in case error codes differ. */
+		ctx->error = error;
+		bm_set_page_io_err(b->bm_pages[idx]);
+		/* Not identical to on disk version of it.
+		 * Is BM_PAGE_IO_ERROR enough? */
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "IO ERROR %d on bitmap page idx %u\n",
+					error, idx);
+	} else {
+		bm_clear_page_io_err(b->bm_pages[idx]);
+		dynamic_dev_dbg(DEV, "bitmap page idx %u completed\n", idx);
 	}
-	if (atomic_dec_and_test(&b->bm_async_io))
-		wake_up(&b->bm_io_wait);
+
+	bm_page_unlock_io(mdev, idx);
+
+	/* FIXME give back to page pool */
+	if (ctx->flags & BM_AIO_COPY_PAGES)
+		put_page(bio->bi_io_vec[0].bv_page);
 
 	bio_put(bio);
+
+	if (atomic_dec_and_test(&ctx->in_flight))
+		complete(&ctx->done);
 }
 
-static void bm_page_io_async(struct drbd_conf *mdev, struct drbd_bitmap *b, int page_nr, int rw) __must_hold(local)
+static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local)
 {
 	/* we are process context. we always get a bio */
 	struct bio *bio = bio_alloc(GFP_KERNEL, 1);
+	struct drbd_conf *mdev = ctx->mdev;
+	struct drbd_bitmap *b = mdev->bitmap;
+	struct page *page;
 	unsigned int len;
+
 	sector_t on_disk_sector =
 		mdev->ldev->md.md_offset + mdev->ldev->md.bm_offset;
 	on_disk_sector += ((sector_t)page_nr) << (PAGE_SHIFT-9);
 
 	/* this might happen with very small
-	 * flexible external meta data device */
+	 * flexible external meta data device,
+	 * or with PAGE_SIZE > 4k */
 	len = min_t(unsigned int, PAGE_SIZE,
 		(drbd_md_last_sector(mdev->ldev) - on_disk_sector + 1)<<9);
 
+	/* serialize IO on this page */
+	bm_page_lock_io(mdev, page_nr);
+	/* before memcpy and submit,
+	 * so it can be redirtied any time */
+	bm_set_page_unchanged(b->bm_pages[page_nr]);
+
+	if (ctx->flags & BM_AIO_COPY_PAGES) {
+		/* FIXME alloc_page is good enough for now, but actually needs
+		 * to use pre-allocated page pool */
+		void *src, *dest;
+		page = alloc_page(__GFP_HIGHMEM|__GFP_WAIT);
+		dest = kmap_atomic(page, KM_USER0);
+		src = kmap_atomic(b->bm_pages[page_nr], KM_USER1);
+		memcpy(dest, src, PAGE_SIZE);
+		kunmap_atomic(src, KM_USER1);
+		kunmap_atomic(dest, KM_USER0);
+		bm_store_page_idx(page, page_nr);
+	} else
+		page = b->bm_pages[page_nr];
+
 	bio->bi_bdev = mdev->ldev->md_bdev;
 	bio->bi_sector = on_disk_sector;
-	bio_add_page(bio, b->bm_pages[page_nr], len, 0);
-	bio->bi_private = b;
+	bio_add_page(bio, page, len, 0);
+	bio->bi_private = ctx;
 	bio->bi_end_io = bm_async_io_complete;
 
-	if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) {
+	if (drbd_insert_fault(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) {
 		bio->bi_rw |= rw;
 		bio_endio(bio, -EIO);
 	} else {
@@ -776,88 +997,84 @@ static void bm_page_io_async(struct drbd_conf *mdev, struct drbd_bitmap *b, int
 	}
 }
 
-# if defined(__LITTLE_ENDIAN)
-	/* nothing to do, on disk == in memory */
-# define bm_cpu_to_lel(x) ((void)0)
-# else
-static void bm_cpu_to_lel(struct drbd_bitmap *b)
-{
-	/* need to cpu_to_lel all the pages ...
-	 * this may be optimized by using
-	 * cpu_to_lel(-1) == -1 and cpu_to_lel(0) == 0;
-	 * the following is still not optimal, but better than nothing */
-	unsigned int i;
-	unsigned long *p_addr, *bm;
-	if (b->bm_set == 0) {
-		/* no page at all; avoid swap if all is 0 */
-		i = b->bm_number_of_pages;
-	} else if (b->bm_set == b->bm_bits) {
-		/* only the last page */
-		i = b->bm_number_of_pages - 1;
-	} else {
-		/* all pages */
-		i = 0;
-	}
-	for (; i < b->bm_number_of_pages; i++) {
-		p_addr = kmap_atomic(b->bm_pages[i], KM_USER0);
-		for (bm = p_addr; bm < p_addr + PAGE_SIZE/sizeof(long); bm++)
-			*bm = cpu_to_lel(*bm);
-		kunmap_atomic(p_addr, KM_USER0);
-	}
-}
-# endif
-/* lel_to_cpu == cpu_to_lel */
-# define bm_lel_to_cpu(x) bm_cpu_to_lel(x)
-
 /*
  * bm_rw: read/write the whole bitmap from/to its on disk location.
  */
-static int bm_rw(struct drbd_conf *mdev, int rw) __must_hold(local)
+static int bm_rw(struct drbd_conf *mdev, int rw, unsigned lazy_writeout_upper_idx) __must_hold(local)
 {
+	struct bm_aio_ctx ctx = {
+		.mdev = mdev,
+		.in_flight = ATOMIC_INIT(1),
+		.done = COMPLETION_INITIALIZER_ONSTACK(ctx.done),
+		.flags = lazy_writeout_upper_idx ? BM_AIO_COPY_PAGES : 0,
+	};
 	struct drbd_bitmap *b = mdev->bitmap;
-	/* sector_t sector; */
-	int bm_words, num_pages, i;
+	int num_pages, i, count = 0;
 	unsigned long now;
 	char ppb[10];
 	int err = 0;
 
-	WARN_ON(!bm_is_locked(b));
-
-	/* no spinlock here, the drbd_bm_lock should be enough! */
-
-	bm_words  = drbd_bm_words(mdev);
-	num_pages = (bm_words*sizeof(long) + PAGE_SIZE-1) >> PAGE_SHIFT;
+	/*
+	 * We are protected against bitmap disappearing/resizing by holding an
+	 * ldev reference (caller must have called get_ldev()).
+	 * For read/write, we are protected against changes to the bitmap by
+	 * the bitmap lock (see drbd_bitmap_io).
+	 * For lazy writeout, we don't care for ongoing changes to the bitmap,
+	 * as we submit copies of pages anyways.
+	 */
+	if (!ctx.flags)
+		WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
 
-	/* on disk bitmap is little endian */
-	if (rw == WRITE)
-		bm_cpu_to_lel(b);
+	num_pages = b->bm_number_of_pages;
 
 	now = jiffies;
-	atomic_set(&b->bm_async_io, num_pages);
-	__clear_bit(BM_MD_IO_ERROR, &b->bm_flags);
 
 	/* let the layers below us try to merge these bios... */
-	for (i = 0; i < num_pages; i++)
-		bm_page_io_async(mdev, b, i, rw);
+	for (i = 0; i < num_pages; i++) {
+		/* ignore completely unchanged pages */
+		if (lazy_writeout_upper_idx && i == lazy_writeout_upper_idx)
+			break;
+		if (rw & WRITE) {
+			if (bm_test_page_unchanged(b->bm_pages[i])) {
+				dynamic_dev_dbg(DEV, "skipped bm write for idx %u\n", i);
+				continue;
+			}
+			/* during lazy writeout,
+			 * ignore those pages not marked for lazy writeout. */
+			if (lazy_writeout_upper_idx &&
+			    !bm_test_page_lazy_writeout(b->bm_pages[i])) {
+				dynamic_dev_dbg(DEV, "skipped bm lazy write for idx %u\n", i);
+				continue;
+			}
+		}
+		atomic_inc(&ctx.in_flight);
+		bm_page_io_async(&ctx, i, rw);
+		++count;
+		cond_resched();
+	}
 
-	drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
-	wait_event(b->bm_io_wait, atomic_read(&b->bm_async_io) == 0);
+	/*
+	 * We initialize ctx.in_flight to one to make sure bm_async_io_complete
+	 * will not complete() early, and decrement / test it here.  If there
+	 * are still some bios in flight, we need to wait for them here.
+	 */
+	if (!atomic_dec_and_test(&ctx.in_flight))
+		wait_for_completion(&ctx.done);
+	dev_info(DEV, "bitmap %s of %u pages took %lu jiffies\n",
+			rw == WRITE ? "WRITE" : "READ",
+			count, jiffies - now);
 
-	if (test_bit(BM_MD_IO_ERROR, &b->bm_flags)) {
+	if (ctx.error) {
 		dev_alert(DEV, "we had at least one MD IO ERROR during bitmap IO\n");
-		drbd_chk_io_error(mdev, 1, TRUE);
-		err = -EIO;
+		drbd_chk_io_error(mdev, 1, true);
+		err = -EIO; /* ctx.error ? */
 	}
 
 	now = jiffies;
 	if (rw == WRITE) {
-		/* swap back endianness */
-		bm_lel_to_cpu(b);
-		/* flush bitmap to stable storage */
 		drbd_md_flush(mdev);
 	} else /* rw == READ */ {
-		/* just read, if necessary adjust endianness */
-		b->bm_set = bm_count_bits_swap_endian(b);
+		b->bm_set = bm_count_bits(b);
 		dev_info(DEV, "recounting of set bits took additional %lu jiffies\n",
 		     jiffies - now);
 	}
@@ -875,112 +1092,128 @@ static int bm_rw(struct drbd_conf *mdev, int rw) __must_hold(local)
  */
 int drbd_bm_read(struct drbd_conf *mdev) __must_hold(local)
 {
-	return bm_rw(mdev, READ);
+	return bm_rw(mdev, READ, 0);
 }
 
 /**
  * drbd_bm_write() - Write the whole bitmap to its on disk location.
  * @mdev:	DRBD device.
+ *
+ * Will only write pages that have changed since last IO.
  */
 int drbd_bm_write(struct drbd_conf *mdev) __must_hold(local)
 {
-	return bm_rw(mdev, WRITE);
+	return bm_rw(mdev, WRITE, 0);
 }
 
 /**
- * drbd_bm_write_sect: Writes a 512 (MD_SECTOR_SIZE) byte piece of the bitmap
+ * drbd_bm_lazy_write_out() - Write bitmap pages 0 to @upper_idx-1, if they have changed.
  * @mdev:	DRBD device.
- * @enr:	Extent number in the resync lru (happens to be sector offset)
- *
- * The BM_EXT_SIZE is on purpose exactly the amount of the bitmap covered
- * by a single sector write. Therefore enr == sector offset from the
- * start of the bitmap.
+ * @upper_idx:	0: write all changed pages; +ve: page index to stop scanning for changed pages
  */
-int drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local)
+int drbd_bm_write_lazy(struct drbd_conf *mdev, unsigned upper_idx) __must_hold(local)
 {
-	sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
-				      + mdev->ldev->md.bm_offset;
-	int bm_words, num_words, offset;
-	int err = 0;
+	return bm_rw(mdev, WRITE, upper_idx);
+}
+
 
-	mutex_lock(&mdev->md_io_mutex);
-	bm_words  = drbd_bm_words(mdev);
-	offset    = S2W(enr);	/* word offset into bitmap */
-	num_words = min(S2W(1), bm_words - offset);
-	if (num_words < S2W(1))
-		memset(page_address(mdev->md_io_page), 0, MD_SECTOR_SIZE);
-	drbd_bm_get_lel(mdev, offset, num_words,
-			page_address(mdev->md_io_page));
-	if (!drbd_md_sync_page_io(mdev, mdev->ldev, on_disk_sector, WRITE)) {
-		int i;
-		err = -EIO;
-		dev_err(DEV, "IO ERROR writing bitmap sector %lu "
-		    "(meta-disk sector %llus)\n",
-		    enr, (unsigned long long)on_disk_sector);
-		drbd_chk_io_error(mdev, 1, TRUE);
-		for (i = 0; i < AL_EXT_PER_BM_SECT; i++)
-			drbd_bm_ALe_set_all(mdev, enr*AL_EXT_PER_BM_SECT+i);
+/**
+ * drbd_bm_write_page: Writes a PAGE_SIZE aligned piece of bitmap
+ * @mdev:	DRBD device.
+ * @idx:	bitmap page index
+ *
+ * We don't want to special case on logical_block_size of the backend device,
+ * so we submit PAGE_SIZE aligned pieces.
+ * Note that on "most" systems, PAGE_SIZE is 4k.
+ *
+ * In case this becomes an issue on systems with larger PAGE_SIZE,
+ * we may want to change this again to write 4k aligned 4k pieces.
+ */
+int drbd_bm_write_page(struct drbd_conf *mdev, unsigned int idx) __must_hold(local)
+{
+	struct bm_aio_ctx ctx = {
+		.mdev = mdev,
+		.in_flight = ATOMIC_INIT(1),
+		.done = COMPLETION_INITIALIZER_ONSTACK(ctx.done),
+		.flags = BM_AIO_COPY_PAGES,
+	};
+
+	if (bm_test_page_unchanged(mdev->bitmap->bm_pages[idx])) {
+		dynamic_dev_dbg(DEV, "skipped bm page write for idx %u\n", idx);
+		return 0;
 	}
+
+	bm_page_io_async(&ctx, idx, WRITE_SYNC);
+	wait_for_completion(&ctx.done);
+
+	if (ctx.error)
+		drbd_chk_io_error(mdev, 1, true);
+		/* that should force detach, so the in memory bitmap will be
+		 * gone in a moment as well. */
+
 	mdev->bm_writ_cnt++;
-	mutex_unlock(&mdev->md_io_mutex);
-	return err;
+	return ctx.error;
 }
 
 /* NOTE
  * find_first_bit returns int, we return unsigned long.
- * should not make much difference anyways, but ...
+ * For this to work on 32bit arch with bitnumbers > (1<<32),
+ * we'd need to return u64, and get a whole lot of other places
+ * fixed where we still use unsigned long.
  *
  * this returns a bit number, NOT a sector!
  */
-#define BPP_MASK ((1UL << (PAGE_SHIFT+3)) - 1)
 static unsigned long __bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo,
 	const int find_zero_bit, const enum km_type km)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
-	unsigned long i = -1UL;
 	unsigned long *p_addr;
-	unsigned long bit_offset; /* bit offset of the mapped page. */
+	unsigned long bit_offset;
+	unsigned i;
+
 
 	if (bm_fo > b->bm_bits) {
 		dev_err(DEV, "bm_fo=%lu bm_bits=%lu\n", bm_fo, b->bm_bits);
+		bm_fo = DRBD_END_OF_BITMAP;
 	} else {
 		while (bm_fo < b->bm_bits) {
-			unsigned long offset;
-			bit_offset = bm_fo & ~BPP_MASK; /* bit offset of the page */
-			offset = bit_offset >> LN2_BPL;    /* word offset of the page */
-			p_addr = __bm_map_paddr(b, offset, km);
+			/* bit offset of the first bit in the page */
+			bit_offset = bm_fo & ~BITS_PER_PAGE_MASK;
+			p_addr = __bm_map_pidx(b, bm_bit_to_page_idx(b, bm_fo), km);
 
 			if (find_zero_bit)
-				i = find_next_zero_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+				i = find_next_zero_bit_le(p_addr,
+						PAGE_SIZE*8, bm_fo & BITS_PER_PAGE_MASK);
 			else
-				i = find_next_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+				i = find_next_bit_le(p_addr,
+						PAGE_SIZE*8, bm_fo & BITS_PER_PAGE_MASK);
 
 			__bm_unmap(p_addr, km);
 			if (i < PAGE_SIZE*8) {
-				i = bit_offset + i;
-				if (i >= b->bm_bits)
+				bm_fo = bit_offset + i;
+				if (bm_fo >= b->bm_bits)
 					break;
 				goto found;
 			}
 			bm_fo = bit_offset + PAGE_SIZE*8;
 		}
-		i = -1UL;
+		bm_fo = DRBD_END_OF_BITMAP;
 	}
  found:
-	return i;
+	return bm_fo;
 }
 
 static unsigned long bm_find_next(struct drbd_conf *mdev,
 	unsigned long bm_fo, const int find_zero_bit)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
-	unsigned long i = -1UL;
+	unsigned long i = DRBD_END_OF_BITMAP;
 
 	ERR_IF(!b) return i;
 	ERR_IF(!b->bm_pages) return i;
 
 	spin_lock_irq(&b->bm_lock);
-	if (bm_is_locked(b))
+	if (BM_DONT_TEST & b->bm_flags)
 		bm_print_lock_info(mdev);
 
 	i = __bm_find_next(mdev, bm_fo, find_zero_bit, KM_IRQ1);
@@ -1006,13 +1239,13 @@ unsigned long drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo
  * you must take drbd_bm_lock() first */
 unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
 {
-	/* WARN_ON(!bm_is_locked(mdev)); */
+	/* WARN_ON(!(BM_DONT_SET & mdev->b->bm_flags)); */
 	return __bm_find_next(mdev, bm_fo, 0, KM_USER1);
 }
 
 unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
 {
-	/* WARN_ON(!bm_is_locked(mdev)); */
+	/* WARN_ON(!(BM_DONT_SET & mdev->b->bm_flags)); */
 	return __bm_find_next(mdev, bm_fo, 1, KM_USER1);
 }
 
@@ -1028,8 +1261,9 @@ static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
 	struct drbd_bitmap *b = mdev->bitmap;
 	unsigned long *p_addr = NULL;
 	unsigned long bitnr;
-	unsigned long last_page_nr = -1UL;
+	unsigned int last_page_nr = -1U;
 	int c = 0;
+	int changed_total = 0;
 
 	if (e >= b->bm_bits) {
 		dev_err(DEV, "ASSERT FAILED: bit_s=%lu bit_e=%lu bm_bits=%lu\n",
@@ -1037,23 +1271,33 @@ static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
 		e = b->bm_bits ? b->bm_bits -1 : 0;
 	}
 	for (bitnr = s; bitnr <= e; bitnr++) {
-		unsigned long offset = bitnr>>LN2_BPL;
-		unsigned long page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+		unsigned int page_nr = bm_bit_to_page_idx(b, bitnr);
 		if (page_nr != last_page_nr) {
 			if (p_addr)
 				__bm_unmap(p_addr, km);
-			p_addr = __bm_map_paddr(b, offset, km);
+			if (c < 0)
+				bm_set_page_lazy_writeout(b->bm_pages[last_page_nr]);
+			else if (c > 0)
+				bm_set_page_need_writeout(b->bm_pages[last_page_nr]);
+			changed_total += c;
+			c = 0;
+			p_addr = __bm_map_pidx(b, page_nr, km);
 			last_page_nr = page_nr;
 		}
 		if (val)
-			c += (0 == __test_and_set_bit(bitnr & BPP_MASK, p_addr));
+			c += (0 == __test_and_set_bit_le(bitnr & BITS_PER_PAGE_MASK, p_addr));
 		else
-			c -= (0 != __test_and_clear_bit(bitnr & BPP_MASK, p_addr));
+			c -= (0 != __test_and_clear_bit_le(bitnr & BITS_PER_PAGE_MASK, p_addr));
 	}
 	if (p_addr)
 		__bm_unmap(p_addr, km);
-	b->bm_set += c;
-	return c;
+	if (c < 0)
+		bm_set_page_lazy_writeout(b->bm_pages[last_page_nr]);
+	else if (c > 0)
+		bm_set_page_need_writeout(b->bm_pages[last_page_nr]);
+	changed_total += c;
+	b->bm_set += changed_total;
+	return changed_total;
 }
 
 /* returns number of bits actually changed.
@@ -1071,7 +1315,7 @@ static int bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
 	ERR_IF(!b->bm_pages) return 0;
 
 	spin_lock_irqsave(&b->bm_lock, flags);
-	if (bm_is_locked(b))
+	if ((val ? BM_DONT_SET : BM_DONT_CLEAR) & b->bm_flags)
 		bm_print_lock_info(mdev);
 
 	c = __bm_change_bits_to(mdev, s, e, val, KM_IRQ1);
@@ -1188,12 +1432,11 @@ int drbd_bm_test_bit(struct drbd_conf *mdev, const unsigned long bitnr)
 	ERR_IF(!b->bm_pages) return 0;
 
 	spin_lock_irqsave(&b->bm_lock, flags);
-	if (bm_is_locked(b))
+	if (BM_DONT_TEST & b->bm_flags)
 		bm_print_lock_info(mdev);
 	if (bitnr < b->bm_bits) {
-		unsigned long offset = bitnr>>LN2_BPL;
-		p_addr = bm_map_paddr(b, offset);
-		i = test_bit(bitnr & BPP_MASK, p_addr) ? 1 : 0;
+		p_addr = bm_map_pidx(b, bm_bit_to_page_idx(b, bitnr));
+		i = test_bit_le(bitnr & BITS_PER_PAGE_MASK, p_addr) ? 1 : 0;
 		bm_unmap(p_addr);
 	} else if (bitnr == b->bm_bits) {
 		i = -1;
@@ -1211,10 +1454,10 @@ int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsi
 {
 	unsigned long flags;
 	struct drbd_bitmap *b = mdev->bitmap;
-	unsigned long *p_addr = NULL, page_nr = -1;
+	unsigned long *p_addr = NULL;
 	unsigned long bitnr;
+	unsigned int page_nr = -1U;
 	int c = 0;
-	size_t w;
 
 	/* If this is called without a bitmap, that is a bug.  But just to be
 	 * robust in case we screwed up elsewhere, in that case pretend there
@@ -1224,20 +1467,20 @@ int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsi
 	ERR_IF(!b->bm_pages) return 1;
 
 	spin_lock_irqsave(&b->bm_lock, flags);
-	if (bm_is_locked(b))
+	if (BM_DONT_TEST & b->bm_flags)
 		bm_print_lock_info(mdev);
 	for (bitnr = s; bitnr <= e; bitnr++) {
-		w = bitnr >> LN2_BPL;
-		if (page_nr != w >> (PAGE_SHIFT - LN2_BPL + 3)) {
-			page_nr = w >> (PAGE_SHIFT - LN2_BPL + 3);
+		unsigned int idx = bm_bit_to_page_idx(b, bitnr);
+		if (page_nr != idx) {
+			page_nr = idx;
 			if (p_addr)
 				bm_unmap(p_addr);
-			p_addr = bm_map_paddr(b, w);
+			p_addr = bm_map_pidx(b, idx);
 		}
 		ERR_IF (bitnr >= b->bm_bits) {
 			dev_err(DEV, "bitnr=%lu bm_bits=%lu\n", bitnr, b->bm_bits);
 		} else {
-			c += (0 != test_bit(bitnr - (page_nr << (PAGE_SHIFT+3)), p_addr));
+			c += (0 != test_bit_le(bitnr - (page_nr << (PAGE_SHIFT+3)), p_addr));
 		}
 	}
 	if (p_addr)
@@ -1272,7 +1515,7 @@ int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr)
 	ERR_IF(!b->bm_pages) return 0;
 
 	spin_lock_irqsave(&b->bm_lock, flags);
-	if (bm_is_locked(b))
+	if (BM_DONT_TEST & b->bm_flags)
 		bm_print_lock_info(mdev);
 
 	s = S2W(enr);
@@ -1280,7 +1523,7 @@ int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr)
 	count = 0;
 	if (s < b->bm_words) {
 		int n = e-s;
-		p_addr = bm_map_paddr(b, s);
+		p_addr = bm_map_pidx(b, bm_word_to_page_idx(b, s));
 		bm = p_addr + MLPP(s);
 		while (n--)
 			count += hweight_long(*bm++);
@@ -1292,18 +1535,20 @@ int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr)
 	return count;
 }
 
-/* set all bits covered by the AL-extent al_enr */
+/* Set all bits covered by the AL-extent al_enr.
+ * Returns number of bits changed. */
 unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
 	unsigned long *p_addr, *bm;
 	unsigned long weight;
-	int count, s, e, i, do_now;
+	unsigned long s, e;
+	int count, i, do_now;
 	ERR_IF(!b) return 0;
 	ERR_IF(!b->bm_pages) return 0;
 
 	spin_lock_irq(&b->bm_lock);
-	if (bm_is_locked(b))
+	if (BM_DONT_SET & b->bm_flags)
 		bm_print_lock_info(mdev);
 	weight = b->bm_set;
 
@@ -1315,7 +1560,7 @@ unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr)
 	count = 0;
 	if (s < b->bm_words) {
 		i = do_now = e-s;
-		p_addr = bm_map_paddr(b, s);
+		p_addr = bm_map_pidx(b, bm_word_to_page_idx(b, s));
 		bm = p_addr + MLPP(s);
 		while (i--) {
 			count += hweight_long(*bm);
@@ -1327,7 +1572,7 @@ unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr)
 		if (e == b->bm_words)
 			b->bm_set -= bm_clear_surplus(b);
 	} else {
-		dev_err(DEV, "start offset (%d) too large in drbd_bm_ALe_set_all\n", s);
+		dev_err(DEV, "start offset (%lu) too large in drbd_bm_ALe_set_all\n", s);
 	}
 	weight = b->bm_set - weight;
 	spin_unlock_irq(&b->bm_lock);
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 3803a034893..b2699bb2e53 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -72,13 +72,6 @@ extern int fault_devs;
 extern char usermode_helper[];
 
 
-#ifndef TRUE
-#define TRUE 1
-#endif
-#ifndef FALSE
-#define FALSE 0
-#endif
-
 /* I don't remember why XCPU ...
  * This is used to wake the asender,
  * and to interrupt sending the sending task
@@ -104,6 +97,7 @@ extern char usermode_helper[];
 #define ID_SYNCER (-1ULL)
 #define ID_VACANT 0
 #define is_syncer_block_id(id) ((id) == ID_SYNCER)
+#define UUID_NEW_BM_OFFSET ((u64)0x0001000000000000ULL)
 
 struct drbd_conf;
 
@@ -137,20 +131,19 @@ enum {
 	DRBD_FAULT_MAX,
 };
 
-#ifdef CONFIG_DRBD_FAULT_INJECTION
 extern unsigned int
 _drbd_insert_fault(struct drbd_conf *mdev, unsigned int type);
+
 static inline int
 drbd_insert_fault(struct drbd_conf *mdev, unsigned int type) {
+#ifdef CONFIG_DRBD_FAULT_INJECTION
 	return fault_rate &&
 		(enable_faults & (1<<type)) &&
 		_drbd_insert_fault(mdev, type);
-}
-#define FAULT_ACTIVE(_m, _t) (drbd_insert_fault((_m), (_t)))
-
 #else
-#define FAULT_ACTIVE(_m, _t) (0)
+	return 0;
 #endif
+}
 
 /* integer division, round _UP_ to the next integer */
 #define div_ceil(A, B) ((A)/(B) + ((A)%(B) ? 1 : 0))
@@ -212,8 +205,10 @@ enum drbd_packets {
 	/* P_CKPT_FENCE_REQ      = 0x25, * currently reserved for protocol D */
 	/* P_CKPT_DISABLE_REQ    = 0x26, * currently reserved for protocol D */
 	P_DELAY_PROBE         = 0x27, /* is used on BOTH sockets */
+	P_OUT_OF_SYNC         = 0x28, /* Mark as out of sync (Outrunning), data socket */
+	P_RS_CANCEL           = 0x29, /* meta: Used to cancel RS_DATA_REQUEST packet by SyncSource */
 
-	P_MAX_CMD	      = 0x28,
+	P_MAX_CMD	      = 0x2A,
 	P_MAY_IGNORE	      = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
 	P_MAX_OPT_CMD	      = 0x101,
 
@@ -269,6 +264,7 @@ static inline const char *cmdname(enum drbd_packets cmd)
 		[P_RS_IS_IN_SYNC]	= "CsumRSIsInSync",
 		[P_COMPRESSED_BITMAP]   = "CBitmap",
 		[P_DELAY_PROBE]         = "DelayProbe",
+		[P_OUT_OF_SYNC]		= "OutOfSync",
 		[P_MAX_CMD]	        = NULL,
 	};
 
@@ -377,7 +373,7 @@ union p_header {
 #define DP_HARDBARRIER	      1 /* depricated */
 #define DP_RW_SYNC	      2 /* equals REQ_SYNC    */
 #define DP_MAY_SET_IN_SYNC    4
-#define DP_UNPLUG             8 /* equals REQ_UNPLUG  */
+#define DP_UNPLUG             8 /* not used anymore   */
 #define DP_FUA               16 /* equals REQ_FUA     */
 #define DP_FLUSH             32 /* equals REQ_FLUSH   */
 #define DP_DISCARD           64 /* equals REQ_DISCARD */
@@ -512,7 +508,7 @@ struct p_sizes {
 	u64	    d_size;  /* size of disk */
 	u64	    u_size;  /* user requested size */
 	u64	    c_size;  /* current exported size */
-	u32	    max_segment_size;  /* Maximal size of a BIO */
+	u32	    max_bio_size;  /* Maximal size of a BIO */
 	u16	    queue_order_type;  /* not yet implemented in DRBD*/
 	u16	    dds_flags; /* use enum dds_flags here. */
 } __packed;
@@ -550,6 +546,13 @@ struct p_discard {
 	u32	    pad;
 } __packed;
 
+struct p_block_desc {
+	struct p_header80 head;
+	u64 sector;
+	u32 blksize;
+	u32 pad;	/* to multiple of 8 Byte */
+} __packed;
+
 /* Valid values for the encoding field.
  * Bump proto version when changing this. */
 enum drbd_bitmap_code {
@@ -619,7 +622,7 @@ DCBP_set_pad_bits(struct p_compressed_bm *p, int n)
 /* one bitmap packet, including the p_header,
  * should fit within one _architecture independend_ page.
  * so we need to use the fixed size 4KiB page size
- * most architechtures have used for a long time.
+ * most architectures have used for a long time.
  */
 #define BM_PACKET_PAYLOAD_BYTES (4096 - sizeof(struct p_header80))
 #define BM_PACKET_WORDS (BM_PACKET_PAYLOAD_BYTES/sizeof(long))
@@ -647,6 +650,7 @@ union p_polymorph {
         struct p_block_req       block_req;
 	struct p_delay_probe93   delay_probe93;
 	struct p_rs_uuid         rs_uuid;
+	struct p_block_desc      block_desc;
 } __packed;
 
 /**********************************************************************/
@@ -677,13 +681,6 @@ static inline enum drbd_thread_state get_t_state(struct drbd_thread *thi)
 	return thi->t_state;
 }
 
-
-/*
- * Having this as the first member of a struct provides sort of "inheritance".
- * "derived" structs can be "drbd_queue_work()"ed.
- * The callback should know and cast back to the descendant struct.
- * drbd_request and drbd_epoch_entry are descendants of drbd_work.
- */
 struct drbd_work;
 typedef int (*drbd_work_cb)(struct drbd_conf *, struct drbd_work *, int cancel);
 struct drbd_work {
@@ -712,9 +709,6 @@ struct drbd_request {
 	 * starting a new epoch...
 	 */
 
-	/* up to here, the struct layout is identical to drbd_epoch_entry;
-	 * we might be able to use that to our advantage...  */
-
 	struct list_head tl_requests; /* ring list in the transfer log */
 	struct bio *master_bio;       /* master bio pointer */
 	unsigned long rq_state; /* see comments above _req_mod() */
@@ -816,7 +810,7 @@ enum {
 
 /* global flag bits */
 enum {
-	CREATE_BARRIER,		/* next P_DATA is preceeded by a P_BARRIER */
+	CREATE_BARRIER,		/* next P_DATA is preceded by a P_BARRIER */
 	SIGNAL_ASENDER,		/* whether asender wants to be interrupted */
 	SEND_PING,		/* whether asender should send a ping asap */
 
@@ -831,7 +825,7 @@ enum {
 	CRASHED_PRIMARY,	/* This node was a crashed primary.
 				 * Gets cleared when the state.conn
 				 * goes into C_CONNECTED state. */
-	WRITE_BM_AFTER_RESYNC,	/* A kmalloc() during resync failed */
+	NO_BARRIER_SUPP,	/* underlying block device doesn't implement barriers */
 	CONSIDER_RESYNC,
 
 	MD_NO_FUA,		/* Users wants us to not use FUA/FLUSH on meta data dev */
@@ -856,10 +850,37 @@ enum {
 	GOT_PING_ACK,		/* set when we receive a ping_ack packet, misc wait gets woken */
 	NEW_CUR_UUID,		/* Create new current UUID when thawing IO */
 	AL_SUSPENDED,		/* Activity logging is currently suspended. */
+	AHEAD_TO_SYNC_SOURCE,   /* Ahead -> SyncSource queued */
 };
 
 struct drbd_bitmap; /* opaque for drbd_conf */
 
+/* definition of bits in bm_flags to be used in drbd_bm_lock
+ * and drbd_bitmap_io and friends. */
+enum bm_flag {
+	/* do we need to kfree, or vfree bm_pages? */
+	BM_P_VMALLOCED = 0x10000, /* internal use only, will be masked out */
+
+	/* currently locked for bulk operation */
+	BM_LOCKED_MASK = 0x7,
+
+	/* in detail, that is: */
+	BM_DONT_CLEAR = 0x1,
+	BM_DONT_SET   = 0x2,
+	BM_DONT_TEST  = 0x4,
+
+	/* (test bit, count bit) allowed (common case) */
+	BM_LOCKED_TEST_ALLOWED = 0x3,
+
+	/* testing bits, as well as setting new bits allowed, but clearing bits
+	 * would be unexpected.  Used during bitmap receive.  Setting new bits
+	 * requires sending of "out-of-sync" information, though. */
+	BM_LOCKED_SET_ALLOWED = 0x1,
+
+	/* clear is not expected while bitmap is locked for bulk operation */
+};
+
+
 /* TODO sort members for performance
  * MAYBE group them further */
 
@@ -925,6 +946,7 @@ struct drbd_md_io {
 struct bm_io_work {
 	struct drbd_work w;
 	char *why;
+	enum bm_flag flags;
 	int (*io_fn)(struct drbd_conf *mdev);
 	void (*done)(struct drbd_conf *mdev, int rv);
 };
@@ -963,9 +985,12 @@ struct drbd_conf {
 	struct drbd_work  resync_work,
 			  unplug_work,
 			  go_diskless,
-			  md_sync_work;
+			  md_sync_work,
+			  start_resync_work;
 	struct timer_list resync_timer;
 	struct timer_list md_sync_timer;
+	struct timer_list start_resync_timer;
+	struct timer_list request_timer;
 #ifdef DRBD_DEBUG_MD_SYNC
 	struct {
 		unsigned int line;
@@ -1000,9 +1025,9 @@ struct drbd_conf {
 	struct hlist_head *tl_hash;
 	unsigned int tl_hash_s;
 
-	/* blocks to sync in this run [unit BM_BLOCK_SIZE] */
+	/* blocks to resync in this run [unit BM_BLOCK_SIZE] */
 	unsigned long rs_total;
-	/* number of sync IOs that failed in this run */
+	/* number of resync blocks that failed in this run */
 	unsigned long rs_failed;
 	/* Syncer's start time [unit jiffies] */
 	unsigned long rs_start;
@@ -1101,7 +1126,8 @@ struct drbd_conf {
 	int c_sync_rate; /* current resync rate after syncer throttle magic */
 	struct fifo_buffer rs_plan_s; /* correction values of resync planer */
 	int rs_in_flight; /* resync sectors in flight (to proxy, in proxy and from proxy) */
-	int rs_planed;    /* resync sectors already planed */
+	int rs_planed;    /* resync sectors already planned */
+	atomic_t ap_in_flight; /* App sectors in flight (waiting for ack) */
 };
 
 static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
@@ -1118,7 +1144,7 @@ static inline unsigned int mdev_to_minor(struct drbd_conf *mdev)
 	return mdev->minor;
 }
 
-/* returns 1 if it was successfull,
+/* returns 1 if it was successful,
  * returns 0 if there was no data socket.
  * so wherever you are going to use the data.socket, e.g. do
  * if (!drbd_get_data_sock(mdev))
@@ -1163,14 +1189,19 @@ enum dds_flags {
 };
 
 extern void drbd_init_set_defaults(struct drbd_conf *mdev);
-extern int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
-			union drbd_state mask, union drbd_state val);
+extern enum drbd_state_rv drbd_change_state(struct drbd_conf *mdev,
+					    enum chg_state_flags f,
+					    union drbd_state mask,
+					    union drbd_state val);
 extern void drbd_force_state(struct drbd_conf *, union drbd_state,
 			union drbd_state);
-extern int _drbd_request_state(struct drbd_conf *, union drbd_state,
-			union drbd_state, enum chg_state_flags);
-extern int __drbd_set_state(struct drbd_conf *, union drbd_state,
-			    enum chg_state_flags, struct completion *done);
+extern enum drbd_state_rv _drbd_request_state(struct drbd_conf *,
+					      union drbd_state,
+					      union drbd_state,
+					      enum chg_state_flags);
+extern enum drbd_state_rv __drbd_set_state(struct drbd_conf *, union drbd_state,
+					   enum chg_state_flags,
+					   struct completion *done);
 extern void print_st_err(struct drbd_conf *, union drbd_state,
 			union drbd_state, int);
 extern int  drbd_thread_start(struct drbd_thread *thi);
@@ -1195,7 +1226,7 @@ extern int drbd_send(struct drbd_conf *mdev, struct socket *sock,
 extern int drbd_send_protocol(struct drbd_conf *mdev);
 extern int drbd_send_uuids(struct drbd_conf *mdev);
 extern int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev);
-extern int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val);
+extern int drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev);
 extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags);
 extern int _drbd_send_state(struct drbd_conf *mdev);
 extern int drbd_send_state(struct drbd_conf *mdev);
@@ -1220,11 +1251,10 @@ extern int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
 			struct p_data *dp, int data_size);
 extern int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
 			    sector_t sector, int blksize, u64 block_id);
+extern int drbd_send_oos(struct drbd_conf *mdev, struct drbd_request *req);
 extern int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
 			   struct drbd_epoch_entry *e);
 extern int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req);
-extern int _drbd_send_barrier(struct drbd_conf *mdev,
-			struct drbd_tl_epoch *barrier);
 extern int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
 			      sector_t sector, int size, u64 block_id);
 extern int drbd_send_drequest_csum(struct drbd_conf *mdev,
@@ -1235,14 +1265,13 @@ extern int drbd_send_ov_request(struct drbd_conf *mdev,sector_t sector,int size)
 
 extern int drbd_send_bitmap(struct drbd_conf *mdev);
 extern int _drbd_send_bitmap(struct drbd_conf *mdev);
-extern int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode);
+extern int drbd_send_sr_reply(struct drbd_conf *mdev, enum drbd_state_rv retcode);
 extern void drbd_free_bc(struct drbd_backing_dev *ldev);
 extern void drbd_mdev_cleanup(struct drbd_conf *mdev);
+void drbd_print_uuids(struct drbd_conf *mdev, const char *text);
 
-/* drbd_meta-data.c (still in drbd_main.c) */
 extern void drbd_md_sync(struct drbd_conf *mdev);
 extern int  drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev);
-/* maybe define them below as inline? */
 extern void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
 extern void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
 extern void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
@@ -1261,10 +1290,12 @@ extern void drbd_md_mark_dirty_(struct drbd_conf *mdev,
 extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
 				 int (*io_fn)(struct drbd_conf *),
 				 void (*done)(struct drbd_conf *, int),
-				 char *why);
+				 char *why, enum bm_flag flags);
+extern int drbd_bitmap_io(struct drbd_conf *mdev,
+		int (*io_fn)(struct drbd_conf *),
+		char *why, enum bm_flag flags);
 extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
 extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
-extern int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why);
 extern void drbd_go_diskless(struct drbd_conf *mdev);
 extern void drbd_ldev_destroy(struct drbd_conf *mdev);
 
@@ -1313,6 +1344,7 @@ struct bm_extent {
 
 #define BME_NO_WRITES  0  /* bm_extent.flags: no more requests on this one! */
 #define BME_LOCKED     1  /* bm_extent.flags: syncer active on this one. */
+#define BME_PRIORITY   2  /* finish resync IO on this extent ASAP! App IO waiting! */
 
 /* drbd_bitmap.c */
 /*
@@ -1390,7 +1422,9 @@ struct bm_extent {
  * you should use 64bit OS for that much storage, anyways. */
 #define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0xffff7fff)
 #else
-#define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0x1LU << 32)
+/* we allow up to 1 PiB now on 64bit architecture with "flexible" meta data */
+#define DRBD_MAX_SECTORS_FLEX (1UL << 51)
+/* corresponds to (1UL << 38) bits right now. */
 #endif
 #endif
 
@@ -1398,7 +1432,7 @@ struct bm_extent {
  * With a value of 8 all IO in one 128K block make it to the same slot of the
  * hash table. */
 #define HT_SHIFT 8
-#define DRBD_MAX_SEGMENT_SIZE (1U<<(9+HT_SHIFT))
+#define DRBD_MAX_BIO_SIZE (1U<<(9+HT_SHIFT))
 
 #define DRBD_MAX_SIZE_H80_PACKET (1 << 15) /* The old header only allows packets up to 32Kib data */
 
@@ -1410,16 +1444,20 @@ extern int  drbd_bm_resize(struct drbd_conf *mdev, sector_t sectors, int set_new
 extern void drbd_bm_cleanup(struct drbd_conf *mdev);
 extern void drbd_bm_set_all(struct drbd_conf *mdev);
 extern void drbd_bm_clear_all(struct drbd_conf *mdev);
+/* set/clear/test only a few bits at a time */
 extern int  drbd_bm_set_bits(
 		struct drbd_conf *mdev, unsigned long s, unsigned long e);
 extern int  drbd_bm_clear_bits(
 		struct drbd_conf *mdev, unsigned long s, unsigned long e);
-/* bm_set_bits variant for use while holding drbd_bm_lock */
+extern int drbd_bm_count_bits(
+	struct drbd_conf *mdev, const unsigned long s, const unsigned long e);
+/* bm_set_bits variant for use while holding drbd_bm_lock,
+ * may process the whole bitmap in one go */
 extern void _drbd_bm_set_bits(struct drbd_conf *mdev,
 		const unsigned long s, const unsigned long e);
 extern int  drbd_bm_test_bit(struct drbd_conf *mdev, unsigned long bitnr);
 extern int  drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr);
-extern int  drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local);
+extern int  drbd_bm_write_page(struct drbd_conf *mdev, unsigned int idx) __must_hold(local);
 extern int  drbd_bm_read(struct drbd_conf *mdev) __must_hold(local);
 extern int  drbd_bm_write(struct drbd_conf *mdev) __must_hold(local);
 extern unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev,
@@ -1427,6 +1465,8 @@ extern unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev,
 extern size_t	     drbd_bm_words(struct drbd_conf *mdev);
 extern unsigned long drbd_bm_bits(struct drbd_conf *mdev);
 extern sector_t      drbd_bm_capacity(struct drbd_conf *mdev);
+
+#define DRBD_END_OF_BITMAP	(~(unsigned long)0)
 extern unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
 /* bm_find_next variants for use while you hold drbd_bm_lock() */
 extern unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
@@ -1437,14 +1477,12 @@ extern int drbd_bm_rs_done(struct drbd_conf *mdev);
 /* for receive_bitmap */
 extern void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset,
 		size_t number, unsigned long *buffer);
-/* for _drbd_send_bitmap and drbd_bm_write_sect */
+/* for _drbd_send_bitmap */
 extern void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset,
 		size_t number, unsigned long *buffer);
 
-extern void drbd_bm_lock(struct drbd_conf *mdev, char *why);
+extern void drbd_bm_lock(struct drbd_conf *mdev, char *why, enum bm_flag flags);
 extern void drbd_bm_unlock(struct drbd_conf *mdev);
-
-extern int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e);
 /* drbd_main.c */
 
 extern struct kmem_cache *drbd_request_cache;
@@ -1467,7 +1505,7 @@ extern void drbd_free_mdev(struct drbd_conf *mdev);
 extern int proc_details;
 
 /* drbd_req */
-extern int drbd_make_request_26(struct request_queue *q, struct bio *bio);
+extern int drbd_make_request(struct request_queue *q, struct bio *bio);
 extern int drbd_read_remote(struct drbd_conf *mdev, struct drbd_request *req);
 extern int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec);
 extern int is_valid_ar_handle(struct drbd_request *, sector_t);
@@ -1482,8 +1520,9 @@ enum determine_dev_size { dev_size_error = -1, unchanged = 0, shrunk = 1, grew =
 extern enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *, enum dds_flags) __must_hold(local);
 extern void resync_after_online_grow(struct drbd_conf *);
 extern void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int) __must_hold(local);
-extern int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role,
-		int force);
+extern enum drbd_state_rv drbd_set_role(struct drbd_conf *mdev,
+					enum drbd_role new_role,
+					int force);
 extern enum drbd_disk_state drbd_try_outdate_peer(struct drbd_conf *mdev);
 extern void drbd_try_outdate_peer_async(struct drbd_conf *mdev);
 extern int drbd_khelper(struct drbd_conf *mdev, char *cmd);
@@ -1499,6 +1538,7 @@ extern int drbd_resync_finished(struct drbd_conf *mdev);
 extern int drbd_md_sync_page_io(struct drbd_conf *mdev,
 		struct drbd_backing_dev *bdev, sector_t sector, int rw);
 extern void drbd_ov_oos_found(struct drbd_conf*, sector_t, int);
+extern void drbd_rs_controller_reset(struct drbd_conf *mdev);
 
 static inline void ov_oos_print(struct drbd_conf *mdev)
 {
@@ -1522,21 +1562,23 @@ extern int w_e_end_csum_rs_req(struct drbd_conf *, struct drbd_work *, int);
 extern int w_e_end_ov_reply(struct drbd_conf *, struct drbd_work *, int);
 extern int w_e_end_ov_req(struct drbd_conf *, struct drbd_work *, int);
 extern int w_ov_finished(struct drbd_conf *, struct drbd_work *, int);
-extern int w_resync_inactive(struct drbd_conf *, struct drbd_work *, int);
+extern int w_resync_timer(struct drbd_conf *, struct drbd_work *, int);
 extern int w_resume_next_sg(struct drbd_conf *, struct drbd_work *, int);
 extern int w_send_write_hint(struct drbd_conf *, struct drbd_work *, int);
-extern int w_make_resync_request(struct drbd_conf *, struct drbd_work *, int);
 extern int w_send_dblock(struct drbd_conf *, struct drbd_work *, int);
 extern int w_send_barrier(struct drbd_conf *, struct drbd_work *, int);
 extern int w_send_read_req(struct drbd_conf *, struct drbd_work *, int);
 extern int w_prev_work_done(struct drbd_conf *, struct drbd_work *, int);
 extern int w_e_reissue(struct drbd_conf *, struct drbd_work *, int);
 extern int w_restart_disk_io(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_oos(struct drbd_conf *, struct drbd_work *, int);
+extern int w_start_resync(struct drbd_conf *, struct drbd_work *, int);
 
 extern void resync_timer_fn(unsigned long data);
+extern void start_resync_timer_fn(unsigned long data);
 
 /* drbd_receiver.c */
-extern int drbd_rs_should_slow_down(struct drbd_conf *mdev);
+extern int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector);
 extern int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
 		const unsigned rw, const int fault_type);
 extern int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list);
@@ -1619,16 +1661,16 @@ extern int drbd_rs_del_all(struct drbd_conf *mdev);
 extern void drbd_rs_failed_io(struct drbd_conf *mdev,
 		sector_t sector, int size);
 extern int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *);
+extern void drbd_advance_rs_marks(struct drbd_conf *mdev, unsigned long still_to_go);
 extern void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector,
 		int size, const char *file, const unsigned int line);
 #define drbd_set_in_sync(mdev, sector, size) \
 	__drbd_set_in_sync(mdev, sector, size, __FILE__, __LINE__)
-extern void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector,
+extern int __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector,
 		int size, const char *file, const unsigned int line);
 #define drbd_set_out_of_sync(mdev, sector, size) \
 	__drbd_set_out_of_sync(mdev, sector, size, __FILE__, __LINE__)
 extern void drbd_al_apply_to_bm(struct drbd_conf *mdev);
-extern void drbd_al_to_on_disk_bm(struct drbd_conf *mdev);
 extern void drbd_al_shrink(struct drbd_conf *mdev);
 
 
@@ -1747,11 +1789,11 @@ static inline void drbd_state_unlock(struct drbd_conf *mdev)
 	wake_up(&mdev->misc_wait);
 }
 
-static inline int _drbd_set_state(struct drbd_conf *mdev,
-				   union drbd_state ns, enum chg_state_flags flags,
-				   struct completion *done)
+static inline enum drbd_state_rv
+_drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
+		enum chg_state_flags flags, struct completion *done)
 {
-	int rv;
+	enum drbd_state_rv rv;
 
 	read_lock(&global_state_lock);
 	rv = __drbd_set_state(mdev, ns, flags, done);
@@ -1982,17 +2024,17 @@ static inline int drbd_send_ping_ack(struct drbd_conf *mdev)
 
 static inline void drbd_thread_stop(struct drbd_thread *thi)
 {
-	_drbd_thread_stop(thi, FALSE, TRUE);
+	_drbd_thread_stop(thi, false, true);
 }
 
 static inline void drbd_thread_stop_nowait(struct drbd_thread *thi)
 {
-	_drbd_thread_stop(thi, FALSE, FALSE);
+	_drbd_thread_stop(thi, false, false);
 }
 
 static inline void drbd_thread_restart_nowait(struct drbd_thread *thi)
 {
-	_drbd_thread_stop(thi, TRUE, FALSE);
+	_drbd_thread_stop(thi, true, false);
 }
 
 /* counts how many answer packets packets we expect from our peer,
@@ -2037,7 +2079,7 @@ static inline void inc_ap_pending(struct drbd_conf *mdev)
 /* counts how many resync-related answers we still expect from the peer
  *		     increase			decrease
  * C_SYNC_TARGET sends P_RS_DATA_REQUEST (and expects P_RS_DATA_REPLY)
- * C_SYNC_SOURCE sends P_RS_DATA_REPLY   (and expects P_WRITE_ACK whith ID_SYNCER)
+ * C_SYNC_SOURCE sends P_RS_DATA_REPLY   (and expects P_WRITE_ACK with ID_SYNCER)
  *					   (or P_NEG_ACK with ID_SYNCER)
  */
 static inline void inc_rs_pending(struct drbd_conf *mdev)
@@ -2146,17 +2188,18 @@ extern int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
 static inline void drbd_get_syncer_progress(struct drbd_conf *mdev,
 		unsigned long *bits_left, unsigned int *per_mil_done)
 {
-	/*
-	 * this is to break it at compile time when we change that
-	 * (we may feel 4TB maximum storage per drbd is not enough)
-	 */
+	/* this is to break it at compile time when we change that, in case we
+	 * want to support more than (1<<32) bits on a 32bit arch. */
 	typecheck(unsigned long, mdev->rs_total);
 
 	/* note: both rs_total and rs_left are in bits, i.e. in
 	 * units of BM_BLOCK_SIZE.
 	 * for the percentage, we don't care. */
 
-	*bits_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
+	if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
+		*bits_left = mdev->ov_left;
+	else
+		*bits_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
 	/* >> 10 to prevent overflow,
 	 * +1 to prevent division by zero */
 	if (*bits_left > mdev->rs_total) {
@@ -2171,10 +2214,19 @@ static inline void drbd_get_syncer_progress(struct drbd_conf *mdev,
 				*bits_left, mdev->rs_total, mdev->rs_failed);
 		*per_mil_done = 0;
 	} else {
-		/* make sure the calculation happens in long context */
-		unsigned long tmp = 1000UL -
-				(*bits_left >> 10)*1000UL
-				/ ((mdev->rs_total >> 10) + 1UL);
+		/* Make sure the division happens in long context.
+		 * We allow up to one petabyte storage right now,
+		 * at a granularity of 4k per bit that is 2**38 bits.
+		 * After shift right and multiplication by 1000,
+		 * this should still fit easily into a 32bit long,
+		 * so we don't need a 64bit division on 32bit arch.
+		 * Note: currently we don't support such large bitmaps on 32bit
+		 * arch anyways, but no harm done to be prepared for it here.
+		 */
+		unsigned int shift = mdev->rs_total >= (1ULL << 32) ? 16 : 10;
+		unsigned long left = *bits_left >> shift;
+		unsigned long total = 1UL + (mdev->rs_total >> shift);
+		unsigned long tmp = 1000UL - left * 1000UL/total;
 		*per_mil_done = tmp;
 	}
 }
@@ -2193,8 +2245,9 @@ static inline int drbd_get_max_buffers(struct drbd_conf *mdev)
 	return mxb;
 }
 
-static inline int drbd_state_is_stable(union drbd_state s)
+static inline int drbd_state_is_stable(struct drbd_conf *mdev)
 {
+	union drbd_state s = mdev->state;
 
 	/* DO NOT add a default clause, we want the compiler to warn us
 	 * for any newly introduced state we may have forgotten to add here */
@@ -2211,11 +2264,9 @@ static inline int drbd_state_is_stable(union drbd_state s)
 	case C_VERIFY_T:
 	case C_PAUSED_SYNC_S:
 	case C_PAUSED_SYNC_T:
-		/* maybe stable, look at the disk state */
-		break;
-
-	/* no new io accepted during tansitional states
-	 * like handshake or teardown */
+	case C_AHEAD:
+	case C_BEHIND:
+		/* transitional states, IO allowed */
 	case C_DISCONNECTING:
 	case C_UNCONNECTED:
 	case C_TIMEOUT:
@@ -2226,7 +2277,15 @@ static inline int drbd_state_is_stable(union drbd_state s)
 	case C_WF_REPORT_PARAMS:
 	case C_STARTING_SYNC_S:
 	case C_STARTING_SYNC_T:
+		break;
+
+		/* Allow IO in BM exchange states with new protocols */
 	case C_WF_BITMAP_S:
+		if (mdev->agreed_pro_version < 96)
+			return 0;
+		break;
+
+		/* no new io accepted in these states */
 	case C_WF_BITMAP_T:
 	case C_WF_SYNC_UUID:
 	case C_MASK:
@@ -2261,41 +2320,47 @@ static inline int is_susp(union drbd_state s)
 	return s.susp || s.susp_nod || s.susp_fen;
 }
 
-static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
+static inline bool may_inc_ap_bio(struct drbd_conf *mdev)
 {
 	int mxb = drbd_get_max_buffers(mdev);
 
 	if (is_susp(mdev->state))
-		return 0;
+		return false;
 	if (test_bit(SUSPEND_IO, &mdev->flags))
-		return 0;
+		return false;
 
 	/* to avoid potential deadlock or bitmap corruption,
 	 * in various places, we only allow new application io
 	 * to start during "stable" states. */
 
 	/* no new io accepted when attaching or detaching the disk */
-	if (!drbd_state_is_stable(mdev->state))
-		return 0;
+	if (!drbd_state_is_stable(mdev))
+		return false;
 
 	/* since some older kernels don't have atomic_add_unless,
 	 * and we are within the spinlock anyways, we have this workaround.  */
 	if (atomic_read(&mdev->ap_bio_cnt) > mxb)
-		return 0;
+		return false;
 	if (test_bit(BITMAP_IO, &mdev->flags))
-		return 0;
-	return 1;
+		return false;
+	return true;
 }
 
-/* I'd like to use wait_event_lock_irq,
- * but I'm not sure when it got introduced,
- * and not sure when it has 3 or 4 arguments */
-static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
+static inline bool inc_ap_bio_cond(struct drbd_conf *mdev, int count)
 {
-	/* compare with after_state_ch,
-	 * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
-	DEFINE_WAIT(wait);
+	bool rv = false;
+
+	spin_lock_irq(&mdev->req_lock);
+	rv = may_inc_ap_bio(mdev);
+	if (rv)
+		atomic_add(count, &mdev->ap_bio_cnt);
+	spin_unlock_irq(&mdev->req_lock);
 
+	return rv;
+}
+
+static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
+{
 	/* we wait here
 	 *    as long as the device is suspended
 	 *    until the bitmap is no longer on the fly during connection
@@ -2304,16 +2369,7 @@ static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
 	 * to avoid races with the reconnect code,
 	 * we need to atomic_inc within the spinlock. */
 
-	spin_lock_irq(&mdev->req_lock);
-	while (!__inc_ap_bio_cond(mdev)) {
-		prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
-		spin_unlock_irq(&mdev->req_lock);
-		schedule();
-		finish_wait(&mdev->misc_wait, &wait);
-		spin_lock_irq(&mdev->req_lock);
-	}
-	atomic_add(count, &mdev->ap_bio_cnt);
-	spin_unlock_irq(&mdev->req_lock);
+	wait_event(mdev->misc_wait, inc_ap_bio_cond(mdev, count));
 }
 
 static inline void dec_ap_bio(struct drbd_conf *mdev)
@@ -2333,9 +2389,11 @@ static inline void dec_ap_bio(struct drbd_conf *mdev)
 	}
 }
 
-static inline void drbd_set_ed_uuid(struct drbd_conf *mdev, u64 val)
+static inline int drbd_set_ed_uuid(struct drbd_conf *mdev, u64 val)
 {
+	int changed = mdev->ed_uuid != val;
 	mdev->ed_uuid = val;
+	return changed;
 }
 
 static inline int seq_cmp(u32 a, u32 b)
@@ -2382,20 +2440,6 @@ static inline int drbd_queue_order_type(struct drbd_conf *mdev)
 	return QUEUE_ORDERED_NONE;
 }
 
-static inline void drbd_blk_run_queue(struct request_queue *q)
-{
-	if (q && q->unplug_fn)
-		q->unplug_fn(q);
-}
-
-static inline void drbd_kick_lo(struct drbd_conf *mdev)
-{
-	if (get_ldev(mdev)) {
-		drbd_blk_run_queue(bdev_get_queue(mdev->ldev->backing_bdev));
-		put_ldev(mdev);
-	}
-}
-
 static inline void drbd_md_flush(struct drbd_conf *mdev)
 {
 	int r;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 29cd0dc9fe4..5b525c179f3 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -85,7 +85,8 @@ MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
 MODULE_DESCRIPTION("drbd - Distributed Replicated Block Device v" REL_VERSION);
 MODULE_VERSION(REL_VERSION);
 MODULE_LICENSE("GPL");
-MODULE_PARM_DESC(minor_count, "Maximum number of drbd devices (1-255)");
+MODULE_PARM_DESC(minor_count, "Maximum number of drbd devices ("
+		 __stringify(DRBD_MINOR_COUNT_MIN) "-" __stringify(DRBD_MINOR_COUNT_MAX) ")");
 MODULE_ALIAS_BLOCKDEV_MAJOR(DRBD_MAJOR);
 
 #include <linux/moduleparam.h>
@@ -115,7 +116,7 @@ module_param(fault_devs, int, 0644);
 #endif
 
 /* module parameter, defined */
-unsigned int minor_count = 32;
+unsigned int minor_count = DRBD_MINOR_COUNT_DEF;
 int disable_sendpage;
 int allow_oos;
 unsigned int cn_idx = CN_IDX_DRBD;
@@ -335,6 +336,7 @@ bail:
 	drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
 }
 
+
 /**
  * _tl_restart() - Walks the transfer log, and applies an action to all requests
  * @mdev:	DRBD device.
@@ -456,7 +458,7 @@ void tl_restart(struct drbd_conf *mdev, enum drbd_req_event what)
 }
 
 /**
- * cl_wide_st_chg() - TRUE if the state change is a cluster wide one
+ * cl_wide_st_chg() - true if the state change is a cluster wide one
  * @mdev:	DRBD device.
  * @os:		old (current) state.
  * @ns:		new (wanted) state.
@@ -473,12 +475,13 @@ static int cl_wide_st_chg(struct drbd_conf *mdev,
 		(os.conn == C_CONNECTED && ns.conn == C_VERIFY_S);
 }
 
-int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
-		      union drbd_state mask, union drbd_state val)
+enum drbd_state_rv
+drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
+		  union drbd_state mask, union drbd_state val)
 {
 	unsigned long flags;
 	union drbd_state os, ns;
-	int rv;
+	enum drbd_state_rv rv;
 
 	spin_lock_irqsave(&mdev->req_lock, flags);
 	os = mdev->state;
@@ -502,20 +505,22 @@ void drbd_force_state(struct drbd_conf *mdev,
 	drbd_change_state(mdev, CS_HARD, mask, val);
 }
 
-static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns);
-static int is_valid_state_transition(struct drbd_conf *,
-				     union drbd_state, union drbd_state);
+static enum drbd_state_rv is_valid_state(struct drbd_conf *, union drbd_state);
+static enum drbd_state_rv is_valid_state_transition(struct drbd_conf *,
+						    union drbd_state,
+						    union drbd_state);
 static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
 				       union drbd_state ns, const char **warn_sync_abort);
 int drbd_send_state_req(struct drbd_conf *,
 			union drbd_state, union drbd_state);
 
-static enum drbd_state_ret_codes _req_st_cond(struct drbd_conf *mdev,
-				    union drbd_state mask, union drbd_state val)
+static enum drbd_state_rv
+_req_st_cond(struct drbd_conf *mdev, union drbd_state mask,
+	     union drbd_state val)
 {
 	union drbd_state os, ns;
 	unsigned long flags;
-	int rv;
+	enum drbd_state_rv rv;
 
 	if (test_and_clear_bit(CL_ST_CHG_SUCCESS, &mdev->flags))
 		return SS_CW_SUCCESS;
@@ -536,7 +541,7 @@ static enum drbd_state_ret_codes _req_st_cond(struct drbd_conf *mdev,
 		if (rv == SS_SUCCESS) {
 			rv = is_valid_state_transition(mdev, ns, os);
 			if (rv == SS_SUCCESS)
-				rv = 0; /* cont waiting, otherwise fail. */
+				rv = SS_UNKNOWN_ERROR; /* cont waiting, otherwise fail. */
 		}
 	}
 	spin_unlock_irqrestore(&mdev->req_lock, flags);
@@ -554,14 +559,14 @@ static enum drbd_state_ret_codes _req_st_cond(struct drbd_conf *mdev,
  * Should not be called directly, use drbd_request_state() or
  * _drbd_request_state().
  */
-static int drbd_req_state(struct drbd_conf *mdev,
-			  union drbd_state mask, union drbd_state val,
-			  enum chg_state_flags f)
+static enum drbd_state_rv
+drbd_req_state(struct drbd_conf *mdev, union drbd_state mask,
+	       union drbd_state val, enum chg_state_flags f)
 {
 	struct completion done;
 	unsigned long flags;
 	union drbd_state os, ns;
-	int rv;
+	enum drbd_state_rv rv;
 
 	init_completion(&done);
 
@@ -636,10 +641,11 @@ abort:
  * Cousin of drbd_request_state(), useful with the CS_WAIT_COMPLETE
  * flag, or when logging of failed state change requests is not desired.
  */
-int _drbd_request_state(struct drbd_conf *mdev,	union drbd_state mask,
-			union drbd_state val,	enum chg_state_flags f)
+enum drbd_state_rv
+_drbd_request_state(struct drbd_conf *mdev, union drbd_state mask,
+		    union drbd_state val, enum chg_state_flags f)
 {
-	int rv;
+	enum drbd_state_rv rv;
 
 	wait_event(mdev->state_wait,
 		   (rv = drbd_req_state(mdev, mask, val, f)) != SS_IN_TRANSIENT_STATE);
@@ -663,8 +669,8 @@ static void print_st(struct drbd_conf *mdev, char *name, union drbd_state ns)
 	    );
 }
 
-void print_st_err(struct drbd_conf *mdev,
-	union drbd_state os, union drbd_state ns, int err)
+void print_st_err(struct drbd_conf *mdev, union drbd_state os,
+	          union drbd_state ns, enum drbd_state_rv err)
 {
 	if (err == SS_IN_TRANSIENT_STATE)
 		return;
@@ -674,32 +680,18 @@ void print_st_err(struct drbd_conf *mdev,
 }
 
 
-#define drbd_peer_str drbd_role_str
-#define drbd_pdsk_str drbd_disk_str
-
-#define drbd_susp_str(A)     ((A) ? "1" : "0")
-#define drbd_aftr_isp_str(A) ((A) ? "1" : "0")
-#define drbd_peer_isp_str(A) ((A) ? "1" : "0")
-#define drbd_user_isp_str(A) ((A) ? "1" : "0")
-
-#define PSC(A) \
-	({ if (ns.A != os.A) { \
-		pbp += sprintf(pbp, #A "( %s -> %s ) ", \
-			      drbd_##A##_str(os.A), \
-			      drbd_##A##_str(ns.A)); \
-	} })
-
 /**
  * is_valid_state() - Returns an SS_ error code if ns is not valid
  * @mdev:	DRBD device.
  * @ns:		State to consider.
  */
-static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
+static enum drbd_state_rv
+is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
 {
 	/* See drbd_state_sw_errors in drbd_strings.c */
 
 	enum drbd_fencing_p fp;
-	int rv = SS_SUCCESS;
+	enum drbd_state_rv rv = SS_SUCCESS;
 
 	fp = FP_DONT_CARE;
 	if (get_ldev(mdev)) {
@@ -762,10 +754,11 @@ static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
  * @ns:		new state.
  * @os:		old state.
  */
-static int is_valid_state_transition(struct drbd_conf *mdev,
-				     union drbd_state ns, union drbd_state os)
+static enum drbd_state_rv
+is_valid_state_transition(struct drbd_conf *mdev, union drbd_state ns,
+			  union drbd_state os)
 {
-	int rv = SS_SUCCESS;
+	enum drbd_state_rv rv = SS_SUCCESS;
 
 	if ((ns.conn == C_STARTING_SYNC_T || ns.conn == C_STARTING_SYNC_S) &&
 	    os.conn > C_CONNECTED)
@@ -800,6 +793,10 @@ static int is_valid_state_transition(struct drbd_conf *mdev,
 	    os.conn < C_CONNECTED)
 		rv = SS_NEED_CONNECTION;
 
+	if ((ns.conn == C_SYNC_TARGET || ns.conn == C_SYNC_SOURCE)
+	    && os.conn < C_WF_REPORT_PARAMS)
+		rv = SS_NEED_CONNECTION; /* No NetworkFailure -> SyncTarget etc... */
+
 	return rv;
 }
 
@@ -817,6 +814,7 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
 				       union drbd_state ns, const char **warn_sync_abort)
 {
 	enum drbd_fencing_p fp;
+	enum drbd_disk_state disk_min, disk_max, pdsk_min, pdsk_max;
 
 	fp = FP_DONT_CARE;
 	if (get_ldev(mdev)) {
@@ -869,56 +867,6 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
 		ns.conn = C_CONNECTED;
 	}
 
-	if (ns.conn >= C_CONNECTED &&
-	    ((ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED) ||
-	     (ns.disk == D_NEGOTIATING && ns.conn == C_WF_BITMAP_T))) {
-		switch (ns.conn) {
-		case C_WF_BITMAP_T:
-		case C_PAUSED_SYNC_T:
-			ns.disk = D_OUTDATED;
-			break;
-		case C_CONNECTED:
-		case C_WF_BITMAP_S:
-		case C_SYNC_SOURCE:
-		case C_PAUSED_SYNC_S:
-			ns.disk = D_UP_TO_DATE;
-			break;
-		case C_SYNC_TARGET:
-			ns.disk = D_INCONSISTENT;
-			dev_warn(DEV, "Implicitly set disk state Inconsistent!\n");
-			break;
-		}
-		if (os.disk == D_OUTDATED && ns.disk == D_UP_TO_DATE)
-			dev_warn(DEV, "Implicitly set disk from Outdated to UpToDate\n");
-	}
-
-	if (ns.conn >= C_CONNECTED &&
-	    (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)) {
-		switch (ns.conn) {
-		case C_CONNECTED:
-		case C_WF_BITMAP_T:
-		case C_PAUSED_SYNC_T:
-		case C_SYNC_TARGET:
-			ns.pdsk = D_UP_TO_DATE;
-			break;
-		case C_WF_BITMAP_S:
-		case C_PAUSED_SYNC_S:
-			/* remap any consistent state to D_OUTDATED,
-			 * but disallow "upgrade" of not even consistent states.
-			 */
-			ns.pdsk =
-				(D_DISKLESS < os.pdsk && os.pdsk < D_OUTDATED)
-				? os.pdsk : D_OUTDATED;
-			break;
-		case C_SYNC_SOURCE:
-			ns.pdsk = D_INCONSISTENT;
-			dev_warn(DEV, "Implicitly set pdsk Inconsistent!\n");
-			break;
-		}
-		if (os.pdsk == D_OUTDATED && ns.pdsk == D_UP_TO_DATE)
-			dev_warn(DEV, "Implicitly set pdsk from Outdated to UpToDate\n");
-	}
-
 	/* Connection breaks down before we finished "Negotiating" */
 	if (ns.conn < C_CONNECTED && ns.disk == D_NEGOTIATING &&
 	    get_ldev_if_state(mdev, D_NEGOTIATING)) {
@@ -933,6 +881,94 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
 		put_ldev(mdev);
 	}
 
+	/* D_CONSISTENT and D_OUTDATED vanish when we get connected */
+	if (ns.conn >= C_CONNECTED && ns.conn < C_AHEAD) {
+		if (ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED)
+			ns.disk = D_UP_TO_DATE;
+		if (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)
+			ns.pdsk = D_UP_TO_DATE;
+	}
+
+	/* Implications of the connection stat on the disk states */
+	disk_min = D_DISKLESS;
+	disk_max = D_UP_TO_DATE;
+	pdsk_min = D_INCONSISTENT;
+	pdsk_max = D_UNKNOWN;
+	switch ((enum drbd_conns)ns.conn) {
+	case C_WF_BITMAP_T:
+	case C_PAUSED_SYNC_T:
+	case C_STARTING_SYNC_T:
+	case C_WF_SYNC_UUID:
+	case C_BEHIND:
+		disk_min = D_INCONSISTENT;
+		disk_max = D_OUTDATED;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_VERIFY_S:
+	case C_VERIFY_T:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_CONNECTED:
+		disk_min = D_DISKLESS;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_DISKLESS;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_WF_BITMAP_S:
+	case C_PAUSED_SYNC_S:
+	case C_STARTING_SYNC_S:
+	case C_AHEAD:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_INCONSISTENT;
+		pdsk_max = D_CONSISTENT; /* D_OUTDATED would be nice. But explicit outdate necessary*/
+		break;
+	case C_SYNC_TARGET:
+		disk_min = D_INCONSISTENT;
+		disk_max = D_INCONSISTENT;
+		pdsk_min = D_UP_TO_DATE;
+		pdsk_max = D_UP_TO_DATE;
+		break;
+	case C_SYNC_SOURCE:
+		disk_min = D_UP_TO_DATE;
+		disk_max = D_UP_TO_DATE;
+		pdsk_min = D_INCONSISTENT;
+		pdsk_max = D_INCONSISTENT;
+		break;
+	case C_STANDALONE:
+	case C_DISCONNECTING:
+	case C_UNCONNECTED:
+	case C_TIMEOUT:
+	case C_BROKEN_PIPE:
+	case C_NETWORK_FAILURE:
+	case C_PROTOCOL_ERROR:
+	case C_TEAR_DOWN:
+	case C_WF_CONNECTION:
+	case C_WF_REPORT_PARAMS:
+	case C_MASK:
+		break;
+	}
+	if (ns.disk > disk_max)
+		ns.disk = disk_max;
+
+	if (ns.disk < disk_min) {
+		dev_warn(DEV, "Implicitly set disk from %s to %s\n",
+			 drbd_disk_str(ns.disk), drbd_disk_str(disk_min));
+		ns.disk = disk_min;
+	}
+	if (ns.pdsk > pdsk_max)
+		ns.pdsk = pdsk_max;
+
+	if (ns.pdsk < pdsk_min) {
+		dev_warn(DEV, "Implicitly set pdsk from %s to %s\n",
+			 drbd_disk_str(ns.pdsk), drbd_disk_str(pdsk_min));
+		ns.pdsk = pdsk_min;
+	}
+
 	if (fp == FP_STONITH &&
 	    (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk > D_OUTDATED) &&
 	    !(os.role == R_PRIMARY && os.conn < C_CONNECTED && os.pdsk > D_OUTDATED))
@@ -961,6 +997,10 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
 /* helper for __drbd_set_state */
 static void set_ov_position(struct drbd_conf *mdev, enum drbd_conns cs)
 {
+	if (mdev->agreed_pro_version < 90)
+		mdev->ov_start_sector = 0;
+	mdev->rs_total = drbd_bm_bits(mdev);
+	mdev->ov_position = 0;
 	if (cs == C_VERIFY_T) {
 		/* starting online verify from an arbitrary position
 		 * does not fit well into the existing protocol.
@@ -970,11 +1010,15 @@ static void set_ov_position(struct drbd_conf *mdev, enum drbd_conns cs)
 		mdev->ov_start_sector = ~(sector_t)0;
 	} else {
 		unsigned long bit = BM_SECT_TO_BIT(mdev->ov_start_sector);
-		if (bit >= mdev->rs_total)
+		if (bit >= mdev->rs_total) {
 			mdev->ov_start_sector =
 				BM_BIT_TO_SECT(mdev->rs_total - 1);
+			mdev->rs_total = 1;
+		} else
+			mdev->rs_total -= bit;
 		mdev->ov_position = mdev->ov_start_sector;
 	}
+	mdev->ov_left = mdev->rs_total;
 }
 
 static void drbd_resume_al(struct drbd_conf *mdev)
@@ -992,12 +1036,12 @@ static void drbd_resume_al(struct drbd_conf *mdev)
  *
  * Caller needs to hold req_lock, and global_state_lock. Do not call directly.
  */
-int __drbd_set_state(struct drbd_conf *mdev,
-		    union drbd_state ns, enum chg_state_flags flags,
-		    struct completion *done)
+enum drbd_state_rv
+__drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
+	         enum chg_state_flags flags, struct completion *done)
 {
 	union drbd_state os;
-	int rv = SS_SUCCESS;
+	enum drbd_state_rv rv = SS_SUCCESS;
 	const char *warn_sync_abort = NULL;
 	struct after_state_chg_work *ascw;
 
@@ -1033,22 +1077,46 @@ int __drbd_set_state(struct drbd_conf *mdev,
 		dev_warn(DEV, "%s aborted.\n", warn_sync_abort);
 
 	{
-		char *pbp, pb[300];
-		pbp = pb;
-		*pbp = 0;
-		PSC(role);
-		PSC(peer);
-		PSC(conn);
-		PSC(disk);
-		PSC(pdsk);
-		if (is_susp(ns) != is_susp(os))
-			pbp += sprintf(pbp, "susp( %s -> %s ) ",
-				       drbd_susp_str(is_susp(os)),
-				       drbd_susp_str(is_susp(ns)));
-		PSC(aftr_isp);
-		PSC(peer_isp);
-		PSC(user_isp);
-		dev_info(DEV, "%s\n", pb);
+	char *pbp, pb[300];
+	pbp = pb;
+	*pbp = 0;
+	if (ns.role != os.role)
+		pbp += sprintf(pbp, "role( %s -> %s ) ",
+			       drbd_role_str(os.role),
+			       drbd_role_str(ns.role));
+	if (ns.peer != os.peer)
+		pbp += sprintf(pbp, "peer( %s -> %s ) ",
+			       drbd_role_str(os.peer),
+			       drbd_role_str(ns.peer));
+	if (ns.conn != os.conn)
+		pbp += sprintf(pbp, "conn( %s -> %s ) ",
+			       drbd_conn_str(os.conn),
+			       drbd_conn_str(ns.conn));
+	if (ns.disk != os.disk)
+		pbp += sprintf(pbp, "disk( %s -> %s ) ",
+			       drbd_disk_str(os.disk),
+			       drbd_disk_str(ns.disk));
+	if (ns.pdsk != os.pdsk)
+		pbp += sprintf(pbp, "pdsk( %s -> %s ) ",
+			       drbd_disk_str(os.pdsk),
+			       drbd_disk_str(ns.pdsk));
+	if (is_susp(ns) != is_susp(os))
+		pbp += sprintf(pbp, "susp( %d -> %d ) ",
+			       is_susp(os),
+			       is_susp(ns));
+	if (ns.aftr_isp != os.aftr_isp)
+		pbp += sprintf(pbp, "aftr_isp( %d -> %d ) ",
+			       os.aftr_isp,
+			       ns.aftr_isp);
+	if (ns.peer_isp != os.peer_isp)
+		pbp += sprintf(pbp, "peer_isp( %d -> %d ) ",
+			       os.peer_isp,
+			       ns.peer_isp);
+	if (ns.user_isp != os.user_isp)
+		pbp += sprintf(pbp, "user_isp( %d -> %d ) ",
+			       os.user_isp,
+			       ns.user_isp);
+	dev_info(DEV, "%s\n", pb);
 	}
 
 	/* solve the race between becoming unconfigured,
@@ -1074,6 +1142,10 @@ int __drbd_set_state(struct drbd_conf *mdev,
 		atomic_inc(&mdev->local_cnt);
 
 	mdev->state = ns;
+
+	if (os.disk == D_ATTACHING && ns.disk >= D_NEGOTIATING)
+		drbd_print_uuids(mdev, "attached to UUIDs");
+
 	wake_up(&mdev->misc_wait);
 	wake_up(&mdev->state_wait);
 
@@ -1081,7 +1153,7 @@ int __drbd_set_state(struct drbd_conf *mdev,
 	if ((os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) &&
 	    ns.conn < C_CONNECTED) {
 		mdev->ov_start_sector =
-			BM_BIT_TO_SECT(mdev->rs_total - mdev->ov_left);
+			BM_BIT_TO_SECT(drbd_bm_bits(mdev) - mdev->ov_left);
 		dev_info(DEV, "Online Verify reached sector %llu\n",
 			(unsigned long long)mdev->ov_start_sector);
 	}
@@ -1106,14 +1178,7 @@ int __drbd_set_state(struct drbd_conf *mdev,
 		unsigned long now = jiffies;
 		int i;
 
-		mdev->ov_position = 0;
-		mdev->rs_total = drbd_bm_bits(mdev);
-		if (mdev->agreed_pro_version >= 90)
-			set_ov_position(mdev, ns.conn);
-		else
-			mdev->ov_start_sector = 0;
-		mdev->ov_left = mdev->rs_total
-			      - BM_SECT_TO_BIT(mdev->ov_position);
+		set_ov_position(mdev, ns.conn);
 		mdev->rs_start = now;
 		mdev->rs_last_events = 0;
 		mdev->rs_last_sect_ev = 0;
@@ -1121,10 +1186,12 @@ int __drbd_set_state(struct drbd_conf *mdev,
 		mdev->ov_last_oos_start = 0;
 
 		for (i = 0; i < DRBD_SYNC_MARKS; i++) {
-			mdev->rs_mark_left[i] = mdev->rs_total;
+			mdev->rs_mark_left[i] = mdev->ov_left;
 			mdev->rs_mark_time[i] = now;
 		}
 
+		drbd_rs_controller_reset(mdev);
+
 		if (ns.conn == C_VERIFY_S) {
 			dev_info(DEV, "Starting Online Verify from sector %llu\n",
 					(unsigned long long)mdev->ov_position);
@@ -1228,6 +1295,26 @@ static void abw_start_sync(struct drbd_conf *mdev, int rv)
 	}
 }
 
+int drbd_bitmap_io_from_worker(struct drbd_conf *mdev,
+		int (*io_fn)(struct drbd_conf *),
+		char *why, enum bm_flag flags)
+{
+	int rv;
+
+	D_ASSERT(current == mdev->worker.task);
+
+	/* open coded non-blocking drbd_suspend_io(mdev); */
+	set_bit(SUSPEND_IO, &mdev->flags);
+
+	drbd_bm_lock(mdev, why, flags);
+	rv = io_fn(mdev);
+	drbd_bm_unlock(mdev);
+
+	drbd_resume_io(mdev);
+
+	return rv;
+}
+
 /**
  * after_state_ch() - Perform after state change actions that may sleep
  * @mdev:	DRBD device.
@@ -1266,16 +1353,14 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 
 	nsm.i = -1;
 	if (ns.susp_nod) {
-		if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED) {
-			if (ns.conn == C_CONNECTED)
-				what = resend, nsm.susp_nod = 0;
-			else /* ns.conn > C_CONNECTED */
-				dev_err(DEV, "Unexpected Resynd going on!\n");
-		}
+		if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)
+			what = resend;
 
 		if (os.disk == D_ATTACHING && ns.disk > D_ATTACHING)
-			what = restart_frozen_disk_io, nsm.susp_nod = 0;
+			what = restart_frozen_disk_io;
 
+		if (what != nothing)
+			nsm.susp_nod = 0;
 	}
 
 	if (ns.susp_fen) {
@@ -1306,13 +1391,30 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 		spin_unlock_irq(&mdev->req_lock);
 	}
 
+	/* Became sync source.  With protocol >= 96, we still need to send out
+	 * the sync uuid now. Need to do that before any drbd_send_state, or
+	 * the other side may go "paused sync" before receiving the sync uuids,
+	 * which is unexpected. */
+	if ((os.conn != C_SYNC_SOURCE && os.conn != C_PAUSED_SYNC_S) &&
+	    (ns.conn == C_SYNC_SOURCE || ns.conn == C_PAUSED_SYNC_S) &&
+	    mdev->agreed_pro_version >= 96 && get_ldev(mdev)) {
+		drbd_gen_and_send_sync_uuid(mdev);
+		put_ldev(mdev);
+	}
+
 	/* Do not change the order of the if above and the two below... */
 	if (os.pdsk == D_DISKLESS && ns.pdsk > D_DISKLESS) {      /* attach on the peer */
 		drbd_send_uuids(mdev);
 		drbd_send_state(mdev);
 	}
-	if (os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S)
-		drbd_queue_bitmap_io(mdev, &drbd_send_bitmap, NULL, "send_bitmap (WFBitMapS)");
+	/* No point in queuing send_bitmap if we don't have a connection
+	 * anymore, so check also the _current_ state, not only the new state
+	 * at the time this work was queued. */
+	if (os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S &&
+	    mdev->state.conn == C_WF_BITMAP_S)
+		drbd_queue_bitmap_io(mdev, &drbd_send_bitmap, NULL,
+				"send_bitmap (WFBitMapS)",
+				BM_LOCKED_TEST_ALLOWED);
 
 	/* Lost contact to peer's copy of the data */
 	if ((os.pdsk >= D_INCONSISTENT &&
@@ -1343,7 +1445,23 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 
 		/* D_DISKLESS Peer becomes secondary */
 		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
-			drbd_al_to_on_disk_bm(mdev);
+			/* We may still be Primary ourselves.
+			 * No harm done if the bitmap still changes,
+			 * redirtied pages will follow later. */
+			drbd_bitmap_io_from_worker(mdev, &drbd_bm_write,
+				"demote diskless peer", BM_LOCKED_SET_ALLOWED);
+		put_ldev(mdev);
+	}
+
+	/* Write out all changed bits on demote.
+	 * Though, no need to da that just yet
+	 * if there is a resync going on still */
+	if (os.role == R_PRIMARY && ns.role == R_SECONDARY &&
+		mdev->state.conn <= C_CONNECTED && get_ldev(mdev)) {
+		/* No changes to the bitmap expected this time, so assert that,
+		 * even though no harm was done if it did change. */
+		drbd_bitmap_io_from_worker(mdev, &drbd_bm_write,
+				"demote", BM_LOCKED_TEST_ALLOWED);
 		put_ldev(mdev);
 	}
 
@@ -1371,15 +1489,23 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
 		drbd_send_state(mdev);
 
+	if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
+		drbd_send_state(mdev);
+
 	/* We are in the progress to start a full sync... */
 	if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
 	    (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S))
-		drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, &abw_start_sync, "set_n_write from StartingSync");
+		/* no other bitmap changes expected during this phase */
+		drbd_queue_bitmap_io(mdev,
+			&drbd_bmio_set_n_write, &abw_start_sync,
+			"set_n_write from StartingSync", BM_LOCKED_TEST_ALLOWED);
 
 	/* We are invalidating our self... */
 	if (os.conn < C_CONNECTED && ns.conn < C_CONNECTED &&
 	    os.disk > D_INCONSISTENT && ns.disk == D_INCONSISTENT)
-		drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, NULL, "set_n_write from invalidate");
+		/* other bitmap operation expected during this phase */
+		drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, NULL,
+			"set_n_write from invalidate", BM_LOCKED_MASK);
 
 	/* first half of local IO error, failure to attach,
 	 * or administrative detach */
@@ -1434,10 +1560,8 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 
 		if (drbd_send_state(mdev))
 			dev_warn(DEV, "Notified peer that I'm now diskless.\n");
-		else
-			dev_err(DEV, "Sending state for being diskless failed\n");
 		/* corresponding get_ldev in __drbd_set_state
-		 * this may finaly trigger drbd_ldev_destroy. */
+		 * this may finally trigger drbd_ldev_destroy. */
 		put_ldev(mdev);
 	}
 
@@ -1459,6 +1583,19 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
 		drbd_send_state(mdev);
 
+	/* This triggers bitmap writeout of potentially still unwritten pages
+	 * if the resync finished cleanly, or aborted because of peer disk
+	 * failure, or because of connection loss.
+	 * For resync aborted because of local disk failure, we cannot do
+	 * any bitmap writeout anymore.
+	 * No harm done if some bits change during this phase.
+	 */
+	if (os.conn > C_CONNECTED && ns.conn <= C_CONNECTED && get_ldev(mdev)) {
+		drbd_queue_bitmap_io(mdev, &drbd_bm_write, NULL,
+			"write from resync_finished", BM_LOCKED_SET_ALLOWED);
+		put_ldev(mdev);
+	}
+
 	/* free tl_hash if we Got thawed and are C_STANDALONE */
 	if (ns.conn == C_STANDALONE && !is_susp(ns) && mdev->tl_hash)
 		drbd_free_tl_hash(mdev);
@@ -1559,7 +1696,7 @@ int drbd_thread_start(struct drbd_thread *thi)
 		if (!try_module_get(THIS_MODULE)) {
 			dev_err(DEV, "Failed to get module reference in drbd_thread_start\n");
 			spin_unlock_irqrestore(&thi->t_lock, flags);
-			return FALSE;
+			return false;
 		}
 
 		init_completion(&thi->stop);
@@ -1576,7 +1713,7 @@ int drbd_thread_start(struct drbd_thread *thi)
 			dev_err(DEV, "Couldn't start thread\n");
 
 			module_put(THIS_MODULE);
-			return FALSE;
+			return false;
 		}
 		spin_lock_irqsave(&thi->t_lock, flags);
 		thi->task = nt;
@@ -1596,7 +1733,7 @@ int drbd_thread_start(struct drbd_thread *thi)
 		break;
 	}
 
-	return TRUE;
+	return true;
 }
 
 
@@ -1694,8 +1831,8 @@ int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
 {
 	int sent, ok;
 
-	ERR_IF(!h) return FALSE;
-	ERR_IF(!size) return FALSE;
+	ERR_IF(!h) return false;
+	ERR_IF(!size) return false;
 
 	h->magic   = BE_DRBD_MAGIC;
 	h->command = cpu_to_be16(cmd);
@@ -1704,8 +1841,8 @@ int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
 	sent = drbd_send(mdev, sock, h, size, msg_flags);
 
 	ok = (sent == size);
-	if (!ok)
-		dev_err(DEV, "short sent %s size=%d sent=%d\n",
+	if (!ok && !signal_pending(current))
+		dev_warn(DEV, "short sent %s size=%d sent=%d\n",
 		    cmdname(cmd), (int)size, sent);
 	return ok;
 }
@@ -1840,7 +1977,7 @@ int drbd_send_protocol(struct drbd_conf *mdev)
 		else {
 			dev_err(DEV, "--dry-run is not supported by peer");
 			kfree(p);
-			return 0;
+			return -1;
 		}
 	}
 	p->conn_flags    = cpu_to_be32(cf);
@@ -1888,12 +2025,36 @@ int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev)
 	return _drbd_send_uuids(mdev, 8);
 }
 
+void drbd_print_uuids(struct drbd_conf *mdev, const char *text)
+{
+	if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+		u64 *uuid = mdev->ldev->md.uuid;
+		dev_info(DEV, "%s %016llX:%016llX:%016llX:%016llX\n",
+		     text,
+		     (unsigned long long)uuid[UI_CURRENT],
+		     (unsigned long long)uuid[UI_BITMAP],
+		     (unsigned long long)uuid[UI_HISTORY_START],
+		     (unsigned long long)uuid[UI_HISTORY_END]);
+		put_ldev(mdev);
+	} else {
+		dev_info(DEV, "%s effective data uuid: %016llX\n",
+				text,
+				(unsigned long long)mdev->ed_uuid);
+	}
+}
 
-int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val)
+int drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev)
 {
 	struct p_rs_uuid p;
+	u64 uuid;
+
+	D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
 
-	p.uuid = cpu_to_be64(val);
+	uuid = mdev->ldev->md.uuid[UI_BITMAP] + UUID_NEW_BM_OFFSET;
+	drbd_uuid_set(mdev, UI_BITMAP, uuid);
+	drbd_print_uuids(mdev, "updated sync UUID");
+	drbd_md_sync(mdev);
+	p.uuid = cpu_to_be64(uuid);
 
 	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SYNC_UUID,
 			     (struct p_header80 *)&p, sizeof(p));
@@ -1921,7 +2082,7 @@ int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags fl
 	p.d_size = cpu_to_be64(d_size);
 	p.u_size = cpu_to_be64(u_size);
 	p.c_size = cpu_to_be64(trigger_reply ? 0 : drbd_get_capacity(mdev->this_bdev));
-	p.max_segment_size = cpu_to_be32(queue_max_segment_size(mdev->rq_queue));
+	p.max_bio_size = cpu_to_be32(queue_max_hw_sectors(mdev->rq_queue) << 9);
 	p.queue_order_type = cpu_to_be16(q_order_type);
 	p.dds_flags = cpu_to_be16(flags);
 
@@ -1972,7 +2133,7 @@ int drbd_send_state_req(struct drbd_conf *mdev,
 			     (struct p_header80 *)&p, sizeof(p));
 }
 
-int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode)
+int drbd_send_sr_reply(struct drbd_conf *mdev, enum drbd_state_rv retcode)
 {
 	struct p_req_state_reply p;
 
@@ -2076,9 +2237,15 @@ int fill_bitmap_rle_bits(struct drbd_conf *mdev,
 	return len;
 }
 
-enum { OK, FAILED, DONE }
+/**
+ * send_bitmap_rle_or_plain
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
 send_bitmap_rle_or_plain(struct drbd_conf *mdev,
-	struct p_header80 *h, struct bm_xfer_ctx *c)
+			 struct p_header80 *h, struct bm_xfer_ctx *c)
 {
 	struct p_compressed_bm *p = (void*)h;
 	unsigned long num_words;
@@ -2088,7 +2255,7 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev,
 	len = fill_bitmap_rle_bits(mdev, p, c);
 
 	if (len < 0)
-		return FAILED;
+		return -EIO;
 
 	if (len) {
 		DCBP_set_code(p, RLE_VLI_Bits);
@@ -2118,11 +2285,14 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev,
 		if (c->bit_offset > c->bm_bits)
 			c->bit_offset = c->bm_bits;
 	}
-	ok = ok ? ((len == 0) ? DONE : OK) : FAILED;
-
-	if (ok == DONE)
-		INFO_bm_xfer_stats(mdev, "send", c);
-	return ok;
+	if (ok) {
+		if (len == 0) {
+			INFO_bm_xfer_stats(mdev, "send", c);
+			return 0;
+		} else
+			return 1;
+	}
+	return -EIO;
 }
 
 /* See the comment at receive_bitmap() */
@@ -2130,16 +2300,16 @@ int _drbd_send_bitmap(struct drbd_conf *mdev)
 {
 	struct bm_xfer_ctx c;
 	struct p_header80 *p;
-	int ret;
+	int err;
 
-	ERR_IF(!mdev->bitmap) return FALSE;
+	ERR_IF(!mdev->bitmap) return false;
 
 	/* maybe we should use some per thread scratch page,
 	 * and allocate that during initial device creation? */
 	p = (struct p_header80 *) __get_free_page(GFP_NOIO);
 	if (!p) {
 		dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
-		return FALSE;
+		return false;
 	}
 
 	if (get_ldev(mdev)) {
@@ -2165,11 +2335,11 @@ int _drbd_send_bitmap(struct drbd_conf *mdev)
 	};
 
 	do {
-		ret = send_bitmap_rle_or_plain(mdev, p, &c);
-	} while (ret == OK);
+		err = send_bitmap_rle_or_plain(mdev, p, &c);
+	} while (err > 0);
 
 	free_page((unsigned long) p);
-	return (ret == DONE);
+	return err == 0;
 }
 
 int drbd_send_bitmap(struct drbd_conf *mdev)
@@ -2192,7 +2362,7 @@ int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr, u32 set_size)
 	p.set_size = cpu_to_be32(set_size);
 
 	if (mdev->state.conn < C_CONNECTED)
-		return FALSE;
+		return false;
 	ok = drbd_send_cmd(mdev, USE_META_SOCKET, P_BARRIER_ACK,
 			(struct p_header80 *)&p, sizeof(p));
 	return ok;
@@ -2220,7 +2390,7 @@ static int _drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
 	p.seq_num  = cpu_to_be32(atomic_add_return(1, &mdev->packet_seq));
 
 	if (!mdev->meta.socket || mdev->state.conn < C_CONNECTED)
-		return FALSE;
+		return false;
 	ok = drbd_send_cmd(mdev, USE_META_SOCKET, cmd,
 				(struct p_header80 *)&p, sizeof(p));
 	return ok;
@@ -2326,8 +2496,8 @@ int drbd_send_ov_request(struct drbd_conf *mdev, sector_t sector, int size)
 }
 
 /* called on sndtimeo
- * returns FALSE if we should retry,
- * TRUE if we think connection is dead
+ * returns false if we should retry,
+ * true if we think connection is dead
  */
 static int we_should_drop_the_connection(struct drbd_conf *mdev, struct socket *sock)
 {
@@ -2340,7 +2510,7 @@ static int we_should_drop_the_connection(struct drbd_conf *mdev, struct socket *
 		|| mdev->state.conn < C_CONNECTED;
 
 	if (drop_it)
-		return TRUE;
+		return true;
 
 	drop_it = !--mdev->ko_count;
 	if (!drop_it) {
@@ -2477,12 +2647,11 @@ static u32 bio_flags_to_wire(struct drbd_conf *mdev, unsigned long bi_rw)
 {
 	if (mdev->agreed_pro_version >= 95)
 		return  (bi_rw & REQ_SYNC ? DP_RW_SYNC : 0) |
-			(bi_rw & REQ_UNPLUG ? DP_UNPLUG : 0) |
 			(bi_rw & REQ_FUA ? DP_FUA : 0) |
 			(bi_rw & REQ_FLUSH ? DP_FLUSH : 0) |
 			(bi_rw & REQ_DISCARD ? DP_DISCARD : 0);
 	else
-		return bi_rw & (REQ_SYNC | REQ_UNPLUG) ? DP_RW_SYNC : 0;
+		return bi_rw & REQ_SYNC ? DP_RW_SYNC : 0;
 }
 
 /* Used to send write requests
@@ -2532,13 +2701,39 @@ int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
 	if (ok && dgs) {
 		dgb = mdev->int_dig_out;
 		drbd_csum_bio(mdev, mdev->integrity_w_tfm, req->master_bio, dgb);
-		ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
+		ok = dgs == drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
 	}
 	if (ok) {
-		if (mdev->net_conf->wire_protocol == DRBD_PROT_A)
+		/* For protocol A, we have to memcpy the payload into
+		 * socket buffers, as we may complete right away
+		 * as soon as we handed it over to tcp, at which point the data
+		 * pages may become invalid.
+		 *
+		 * For data-integrity enabled, we copy it as well, so we can be
+		 * sure that even if the bio pages may still be modified, it
+		 * won't change the data on the wire, thus if the digest checks
+		 * out ok after sending on this side, but does not fit on the
+		 * receiving side, we sure have detected corruption elsewhere.
+		 */
+		if (mdev->net_conf->wire_protocol == DRBD_PROT_A || dgs)
 			ok = _drbd_send_bio(mdev, req->master_bio);
 		else
 			ok = _drbd_send_zc_bio(mdev, req->master_bio);
+
+		/* double check digest, sometimes buffers have been modified in flight. */
+		if (dgs > 0 && dgs <= 64) {
+			/* 64 byte, 512 bit, is the larges digest size
+			 * currently supported in kernel crypto. */
+			unsigned char digest[64];
+			drbd_csum_bio(mdev, mdev->integrity_w_tfm, req->master_bio, digest);
+			if (memcmp(mdev->int_dig_out, digest, dgs)) {
+				dev_warn(DEV,
+					"Digest mismatch, buffer modified by upper layers during write: %llus +%u\n",
+					(unsigned long long)req->sector, req->size);
+			}
+		} /* else if (dgs > 64) {
+		     ... Be noisy about digest too large ...
+		} */
 	}
 
 	drbd_put_data_sock(mdev);
@@ -2588,7 +2783,7 @@ int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
 	if (ok && dgs) {
 		dgb = mdev->int_dig_out;
 		drbd_csum_ee(mdev, mdev->integrity_w_tfm, e, dgb);
-		ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
+		ok = dgs == drbd_send(mdev, mdev->data.socket, dgb, dgs, 0);
 	}
 	if (ok)
 		ok = _drbd_send_zc_ee(mdev, e);
@@ -2598,6 +2793,16 @@ int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
 	return ok;
 }
 
+int drbd_send_oos(struct drbd_conf *mdev, struct drbd_request *req)
+{
+	struct p_block_desc p;
+
+	p.sector  = cpu_to_be64(req->sector);
+	p.blksize = cpu_to_be32(req->size);
+
+	return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_OUT_OF_SYNC, &p.head, sizeof(p));
+}
+
 /*
   drbd_send distinguishes two cases:
 
@@ -2719,35 +2924,6 @@ static int drbd_release(struct gendisk *gd, fmode_t mode)
 	return 0;
 }
 
-static void drbd_unplug_fn(struct request_queue *q)
-{
-	struct drbd_conf *mdev = q->queuedata;
-
-	/* unplug FIRST */
-	spin_lock_irq(q->queue_lock);
-	blk_remove_plug(q);
-	spin_unlock_irq(q->queue_lock);
-
-	/* only if connected */
-	spin_lock_irq(&mdev->req_lock);
-	if (mdev->state.pdsk >= D_INCONSISTENT && mdev->state.conn >= C_CONNECTED) {
-		D_ASSERT(mdev->state.role == R_PRIMARY);
-		if (test_and_clear_bit(UNPLUG_REMOTE, &mdev->flags)) {
-			/* add to the data.work queue,
-			 * unless already queued.
-			 * XXX this might be a good addition to drbd_queue_work
-			 * anyways, to detect "double queuing" ... */
-			if (list_empty(&mdev->unplug_work.list))
-				drbd_queue_work(&mdev->data.work,
-						&mdev->unplug_work);
-		}
-	}
-	spin_unlock_irq(&mdev->req_lock);
-
-	if (mdev->state.disk >= D_INCONSISTENT)
-		drbd_kick_lo(mdev);
-}
-
 static void drbd_set_defaults(struct drbd_conf *mdev)
 {
 	/* This way we get a compile error when sync_conf grows,
@@ -2800,6 +2976,7 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	atomic_set(&mdev->pp_in_use_by_net, 0);
 	atomic_set(&mdev->rs_sect_in, 0);
 	atomic_set(&mdev->rs_sect_ev, 0);
+	atomic_set(&mdev->ap_in_flight, 0);
 
 	mutex_init(&mdev->md_io_mutex);
 	mutex_init(&mdev->data.mutex);
@@ -2828,19 +3005,27 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	INIT_LIST_HEAD(&mdev->unplug_work.list);
 	INIT_LIST_HEAD(&mdev->go_diskless.list);
 	INIT_LIST_HEAD(&mdev->md_sync_work.list);
+	INIT_LIST_HEAD(&mdev->start_resync_work.list);
 	INIT_LIST_HEAD(&mdev->bm_io_work.w.list);
 
-	mdev->resync_work.cb  = w_resync_inactive;
+	mdev->resync_work.cb  = w_resync_timer;
 	mdev->unplug_work.cb  = w_send_write_hint;
 	mdev->go_diskless.cb  = w_go_diskless;
 	mdev->md_sync_work.cb = w_md_sync;
 	mdev->bm_io_work.w.cb = w_bitmap_io;
+	mdev->start_resync_work.cb = w_start_resync;
 	init_timer(&mdev->resync_timer);
 	init_timer(&mdev->md_sync_timer);
+	init_timer(&mdev->start_resync_timer);
+	init_timer(&mdev->request_timer);
 	mdev->resync_timer.function = resync_timer_fn;
 	mdev->resync_timer.data = (unsigned long) mdev;
 	mdev->md_sync_timer.function = md_sync_timer_fn;
 	mdev->md_sync_timer.data = (unsigned long) mdev;
+	mdev->start_resync_timer.function = start_resync_timer_fn;
+	mdev->start_resync_timer.data = (unsigned long) mdev;
+	mdev->request_timer.function = request_timer_fn;
+	mdev->request_timer.data = (unsigned long) mdev;
 
 	init_waitqueue_head(&mdev->misc_wait);
 	init_waitqueue_head(&mdev->state_wait);
@@ -2911,6 +3096,8 @@ void drbd_mdev_cleanup(struct drbd_conf *mdev)
 	D_ASSERT(list_empty(&mdev->resync_work.list));
 	D_ASSERT(list_empty(&mdev->unplug_work.list));
 	D_ASSERT(list_empty(&mdev->go_diskless.list));
+
+	drbd_set_defaults(mdev);
 }
 
 
@@ -2953,7 +3140,7 @@ static void drbd_destroy_mempools(void)
 static int drbd_create_mempools(void)
 {
 	struct page *page;
-	const int number = (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE) * minor_count;
+	const int number = (DRBD_MAX_BIO_SIZE/PAGE_SIZE) * minor_count;
 	int i;
 
 	/* prepare our caches and mempools */
@@ -3117,11 +3304,20 @@ static void drbd_cleanup(void)
 
 	unregister_reboot_notifier(&drbd_notifier);
 
+	/* first remove proc,
+	 * drbdsetup uses it's presence to detect
+	 * whether DRBD is loaded.
+	 * If we would get stuck in proc removal,
+	 * but have netlink already deregistered,
+	 * some drbdsetup commands may wait forever
+	 * for an answer.
+	 */
+	if (drbd_proc)
+		remove_proc_entry("drbd", NULL);
+
 	drbd_nl_cleanup();
 
 	if (minor_table) {
-		if (drbd_proc)
-			remove_proc_entry("drbd", NULL);
 		i = minor_count;
 		while (i--)
 			drbd_delete_device(i);
@@ -3149,7 +3345,7 @@ static int drbd_congested(void *congested_data, int bdi_bits)
 	char reason = '-';
 	int r = 0;
 
-	if (!__inc_ap_bio_cond(mdev)) {
+	if (!may_inc_ap_bio(mdev)) {
 		/* DRBD has frozen IO */
 		r = bdi_bits;
 		reason = 'd';
@@ -3202,7 +3398,7 @@ struct drbd_conf *drbd_new_device(unsigned int minor)
 		goto out_no_disk;
 	mdev->vdisk = disk;
 
-	set_disk_ro(disk, TRUE);
+	set_disk_ro(disk, true);
 
 	disk->queue = q;
 	disk->major = DRBD_MAJOR;
@@ -3218,13 +3414,11 @@ struct drbd_conf *drbd_new_device(unsigned int minor)
 	q->backing_dev_info.congested_fn = drbd_congested;
 	q->backing_dev_info.congested_data = mdev;
 
-	blk_queue_make_request(q, drbd_make_request_26);
-	blk_queue_max_segment_size(q, DRBD_MAX_SEGMENT_SIZE);
+	blk_queue_make_request(q, drbd_make_request);
+	blk_queue_max_hw_sectors(q, DRBD_MAX_BIO_SIZE >> 9);
 	blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
 	blk_queue_merge_bvec(q, drbd_merge_bvec);
-	q->queue_lock = &mdev->req_lock; /* needed since we use */
-		/* plugging on a queue, that actually has no requests! */
-	q->unplug_fn = drbd_unplug_fn;
+	q->queue_lock = &mdev->req_lock;
 
 	mdev->md_io_page = alloc_page(GFP_KERNEL);
 	if (!mdev->md_io_page)
@@ -3283,6 +3477,7 @@ void drbd_free_mdev(struct drbd_conf *mdev)
 	put_disk(mdev->vdisk);
 	blk_cleanup_queue(mdev->rq_queue);
 	free_cpumask_var(mdev->cpu_mask);
+	drbd_free_tl_hash(mdev);
 	kfree(mdev);
 }
 
@@ -3298,7 +3493,7 @@ int __init drbd_init(void)
 		return -EINVAL;
 	}
 
-	if (1 > minor_count || minor_count > 255) {
+	if (minor_count < DRBD_MINOR_COUNT_MIN || minor_count > DRBD_MINOR_COUNT_MAX) {
 		printk(KERN_ERR
 			"drbd: invalid minor_count (%d)\n", minor_count);
 #ifdef MODULE
@@ -3480,7 +3675,7 @@ void drbd_md_sync(struct drbd_conf *mdev)
 	if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
 		/* this was a try anyways ... */
 		dev_err(DEV, "meta data update failed!\n");
-		drbd_chk_io_error(mdev, 1, TRUE);
+		drbd_chk_io_error(mdev, 1, true);
 	}
 
 	/* Update mdev->ldev->md.la_size_sect,
@@ -3496,7 +3691,7 @@ void drbd_md_sync(struct drbd_conf *mdev)
  * @mdev:	DRBD device.
  * @bdev:	Device from which the meta data should be read in.
  *
- * Return 0 (NO_ERROR) on success, and an enum drbd_ret_codes in case
+ * Return 0 (NO_ERROR) on success, and an enum drbd_ret_code in case
  * something goes wrong.  Currently only: ERR_IO_MD_DISK, ERR_MD_INVALID.
  */
 int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
@@ -3511,7 +3706,7 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
 	buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
 
 	if (!drbd_md_sync_page_io(mdev, bdev, bdev->md.md_offset, READ)) {
-		/* NOTE: cant do normal error processing here as this is
+		/* NOTE: can't do normal error processing here as this is
 		   called BEFORE disk is attached */
 		dev_err(DEV, "Error while reading metadata.\n");
 		rv = ERR_IO_MD_DISK;
@@ -3566,28 +3761,6 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
 	return rv;
 }
 
-static void debug_drbd_uuid(struct drbd_conf *mdev, enum drbd_uuid_index index)
-{
-	static char *uuid_str[UI_EXTENDED_SIZE] = {
-		[UI_CURRENT] = "CURRENT",
-		[UI_BITMAP] = "BITMAP",
-		[UI_HISTORY_START] = "HISTORY_START",
-		[UI_HISTORY_END] = "HISTORY_END",
-		[UI_SIZE] = "SIZE",
-		[UI_FLAGS] = "FLAGS",
-	};
-
-	if (index >= UI_EXTENDED_SIZE) {
-		dev_warn(DEV, " uuid_index >= EXTENDED_SIZE\n");
-		return;
-	}
-
-	dynamic_dev_dbg(DEV, " uuid[%s] now %016llX\n",
-		 uuid_str[index],
-		 (unsigned long long)mdev->ldev->md.uuid[index]);
-}
-
-
 /**
  * drbd_md_mark_dirty() - Mark meta data super block as dirty
  * @mdev:	DRBD device.
@@ -3617,10 +3790,8 @@ static void drbd_uuid_move_history(struct drbd_conf *mdev) __must_hold(local)
 {
 	int i;
 
-	for (i = UI_HISTORY_START; i < UI_HISTORY_END; i++) {
+	for (i = UI_HISTORY_START; i < UI_HISTORY_END; i++)
 		mdev->ldev->md.uuid[i+1] = mdev->ldev->md.uuid[i];
-		debug_drbd_uuid(mdev, i+1);
-	}
 }
 
 void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
@@ -3635,7 +3806,6 @@ void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
 	}
 
 	mdev->ldev->md.uuid[idx] = val;
-	debug_drbd_uuid(mdev, idx);
 	drbd_md_mark_dirty(mdev);
 }
 
@@ -3645,7 +3815,6 @@ void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
 	if (mdev->ldev->md.uuid[idx]) {
 		drbd_uuid_move_history(mdev);
 		mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[idx];
-		debug_drbd_uuid(mdev, UI_HISTORY_START);
 	}
 	_drbd_uuid_set(mdev, idx, val);
 }
@@ -3660,14 +3829,16 @@ void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
 void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local)
 {
 	u64 val;
+	unsigned long long bm_uuid = mdev->ldev->md.uuid[UI_BITMAP];
+
+	if (bm_uuid)
+		dev_warn(DEV, "bm UUID was already set: %llX\n", bm_uuid);
 
-	dev_info(DEV, "Creating new current UUID\n");
-	D_ASSERT(mdev->ldev->md.uuid[UI_BITMAP] == 0);
 	mdev->ldev->md.uuid[UI_BITMAP] = mdev->ldev->md.uuid[UI_CURRENT];
-	debug_drbd_uuid(mdev, UI_BITMAP);
 
 	get_random_bytes(&val, sizeof(u64));
 	_drbd_uuid_set(mdev, UI_CURRENT, val);
+	drbd_print_uuids(mdev, "new current UUID");
 	/* get it to stable storage _now_ */
 	drbd_md_sync(mdev);
 }
@@ -3681,16 +3852,12 @@ void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local)
 		drbd_uuid_move_history(mdev);
 		mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[UI_BITMAP];
 		mdev->ldev->md.uuid[UI_BITMAP] = 0;
-		debug_drbd_uuid(mdev, UI_HISTORY_START);
-		debug_drbd_uuid(mdev, UI_BITMAP);
 	} else {
-		if (mdev->ldev->md.uuid[UI_BITMAP])
-			dev_warn(DEV, "bm UUID already set");
+		unsigned long long bm_uuid = mdev->ldev->md.uuid[UI_BITMAP];
+		if (bm_uuid)
+			dev_warn(DEV, "bm UUID was already set: %llX\n", bm_uuid);
 
-		mdev->ldev->md.uuid[UI_BITMAP] = val;
-		mdev->ldev->md.uuid[UI_BITMAP] &= ~((u64)1);
-
-		debug_drbd_uuid(mdev, UI_BITMAP);
+		mdev->ldev->md.uuid[UI_BITMAP] = val & ~((u64)1);
 	}
 	drbd_md_mark_dirty(mdev);
 }
@@ -3746,15 +3913,19 @@ int drbd_bmio_clear_n_write(struct drbd_conf *mdev)
 static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused)
 {
 	struct bm_io_work *work = container_of(w, struct bm_io_work, w);
-	int rv;
+	int rv = -EIO;
 
 	D_ASSERT(atomic_read(&mdev->ap_bio_cnt) == 0);
 
-	drbd_bm_lock(mdev, work->why);
-	rv = work->io_fn(mdev);
-	drbd_bm_unlock(mdev);
+	if (get_ldev(mdev)) {
+		drbd_bm_lock(mdev, work->why, work->flags);
+		rv = work->io_fn(mdev);
+		drbd_bm_unlock(mdev);
+		put_ldev(mdev);
+	}
 
 	clear_bit(BITMAP_IO, &mdev->flags);
+	smp_mb__after_clear_bit();
 	wake_up(&mdev->misc_wait);
 
 	if (work->done)
@@ -3762,6 +3933,7 @@ static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused)
 
 	clear_bit(BITMAP_IO_QUEUED, &mdev->flags);
 	work->why = NULL;
+	work->flags = 0;
 
 	return 1;
 }
@@ -3816,7 +3988,7 @@ void drbd_go_diskless(struct drbd_conf *mdev)
 void drbd_queue_bitmap_io(struct drbd_conf *mdev,
 			  int (*io_fn)(struct drbd_conf *),
 			  void (*done)(struct drbd_conf *, int),
-			  char *why)
+			  char *why, enum bm_flag flags)
 {
 	D_ASSERT(current == mdev->worker.task);
 
@@ -3830,15 +4002,15 @@ void drbd_queue_bitmap_io(struct drbd_conf *mdev,
 	mdev->bm_io_work.io_fn = io_fn;
 	mdev->bm_io_work.done = done;
 	mdev->bm_io_work.why = why;
+	mdev->bm_io_work.flags = flags;
 
+	spin_lock_irq(&mdev->req_lock);
 	set_bit(BITMAP_IO, &mdev->flags);
 	if (atomic_read(&mdev->ap_bio_cnt) == 0) {
-		if (list_empty(&mdev->bm_io_work.w.list)) {
-			set_bit(BITMAP_IO_QUEUED, &mdev->flags);
+		if (!test_and_set_bit(BITMAP_IO_QUEUED, &mdev->flags))
 			drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
-		} else
-			dev_err(DEV, "FIXME avoided double queuing bm_io_work\n");
 	}
+	spin_unlock_irq(&mdev->req_lock);
 }
 
 /**
@@ -3850,19 +4022,22 @@ void drbd_queue_bitmap_io(struct drbd_conf *mdev,
  * freezes application IO while that the actual IO operations runs. This
  * functions MAY NOT be called from worker context.
  */
-int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why)
+int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *),
+		char *why, enum bm_flag flags)
 {
 	int rv;
 
 	D_ASSERT(current != mdev->worker.task);
 
-	drbd_suspend_io(mdev);
+	if ((flags & BM_LOCKED_SET_ALLOWED) == 0)
+		drbd_suspend_io(mdev);
 
-	drbd_bm_lock(mdev, why);
+	drbd_bm_lock(mdev, why, flags);
 	rv = io_fn(mdev);
 	drbd_bm_unlock(mdev);
 
-	drbd_resume_io(mdev);
+	if ((flags & BM_LOCKED_SET_ALLOWED) == 0)
+		drbd_resume_io(mdev);
 
 	return rv;
 }
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index fe81c851ca8..03b29f78a37 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -288,10 +288,11 @@ void drbd_try_outdate_peer_async(struct drbd_conf *mdev)
 		dev_err(DEV, "out of mem, failed to invoke fence-peer helper\n");
 }
 
-int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
+enum drbd_state_rv
+drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 {
 	const int max_tries = 4;
-	int r = 0;
+	enum drbd_state_rv rv = SS_UNKNOWN_ERROR;
 	int try = 0;
 	int forced = 0;
 	union drbd_state mask, val;
@@ -306,17 +307,17 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 	val.i  = 0; val.role  = new_role;
 
 	while (try++ < max_tries) {
-		r = _drbd_request_state(mdev, mask, val, CS_WAIT_COMPLETE);
+		rv = _drbd_request_state(mdev, mask, val, CS_WAIT_COMPLETE);
 
 		/* in case we first succeeded to outdate,
 		 * but now suddenly could establish a connection */
-		if (r == SS_CW_FAILED_BY_PEER && mask.pdsk != 0) {
+		if (rv == SS_CW_FAILED_BY_PEER && mask.pdsk != 0) {
 			val.pdsk = 0;
 			mask.pdsk = 0;
 			continue;
 		}
 
-		if (r == SS_NO_UP_TO_DATE_DISK && force &&
+		if (rv == SS_NO_UP_TO_DATE_DISK && force &&
 		    (mdev->state.disk < D_UP_TO_DATE &&
 		     mdev->state.disk >= D_INCONSISTENT)) {
 			mask.disk = D_MASK;
@@ -325,7 +326,7 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 			continue;
 		}
 
-		if (r == SS_NO_UP_TO_DATE_DISK &&
+		if (rv == SS_NO_UP_TO_DATE_DISK &&
 		    mdev->state.disk == D_CONSISTENT && mask.pdsk == 0) {
 			D_ASSERT(mdev->state.pdsk == D_UNKNOWN);
 			nps = drbd_try_outdate_peer(mdev);
@@ -341,9 +342,9 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 			continue;
 		}
 
-		if (r == SS_NOTHING_TO_DO)
+		if (rv == SS_NOTHING_TO_DO)
 			goto fail;
-		if (r == SS_PRIMARY_NOP && mask.pdsk == 0) {
+		if (rv == SS_PRIMARY_NOP && mask.pdsk == 0) {
 			nps = drbd_try_outdate_peer(mdev);
 
 			if (force && nps > D_OUTDATED) {
@@ -356,25 +357,24 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 
 			continue;
 		}
-		if (r == SS_TWO_PRIMARIES) {
+		if (rv == SS_TWO_PRIMARIES) {
 			/* Maybe the peer is detected as dead very soon...
 			   retry at most once more in this case. */
-			__set_current_state(TASK_INTERRUPTIBLE);
-			schedule_timeout((mdev->net_conf->ping_timeo+1)*HZ/10);
+			schedule_timeout_interruptible((mdev->net_conf->ping_timeo+1)*HZ/10);
 			if (try < max_tries)
 				try = max_tries - 1;
 			continue;
 		}
-		if (r < SS_SUCCESS) {
-			r = _drbd_request_state(mdev, mask, val,
+		if (rv < SS_SUCCESS) {
+			rv = _drbd_request_state(mdev, mask, val,
 						CS_VERBOSE + CS_WAIT_COMPLETE);
-			if (r < SS_SUCCESS)
+			if (rv < SS_SUCCESS)
 				goto fail;
 		}
 		break;
 	}
 
-	if (r < SS_SUCCESS)
+	if (rv < SS_SUCCESS)
 		goto fail;
 
 	if (forced)
@@ -384,7 +384,7 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 	wait_event(mdev->misc_wait, atomic_read(&mdev->ap_pending_cnt) == 0);
 
 	if (new_role == R_SECONDARY) {
-		set_disk_ro(mdev->vdisk, TRUE);
+		set_disk_ro(mdev->vdisk, true);
 		if (get_ldev(mdev)) {
 			mdev->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
 			put_ldev(mdev);
@@ -394,7 +394,7 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 			mdev->net_conf->want_lose = 0;
 			put_net_conf(mdev);
 		}
-		set_disk_ro(mdev->vdisk, FALSE);
+		set_disk_ro(mdev->vdisk, false);
 		if (get_ldev(mdev)) {
 			if (((mdev->state.conn < C_CONNECTED ||
 			       mdev->state.pdsk <= D_FAILED)
@@ -406,10 +406,8 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 		}
 	}
 
-	if ((new_role == R_SECONDARY) && get_ldev(mdev)) {
-		drbd_al_to_on_disk_bm(mdev);
-		put_ldev(mdev);
-	}
+	/* writeout of activity log covered areas of the bitmap
+	 * to stable storage done in after state change already */
 
 	if (mdev->state.conn >= C_WF_REPORT_PARAMS) {
 		/* if this was forced, we should consider sync */
@@ -423,7 +421,7 @@ int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
 	kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
  fail:
 	mutex_unlock(&mdev->state_mutex);
-	return r;
+	return rv;
 }
 
 static struct drbd_conf *ensure_mdev(int minor, int create)
@@ -528,17 +526,19 @@ static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
 	}
 }
 
+/* input size is expected to be in KB */
 char *ppsize(char *buf, unsigned long long size)
 {
-	/* Needs 9 bytes at max. */
+	/* Needs 9 bytes at max including trailing NUL:
+	 * -1ULL ==> "16384 EB" */
 	static char units[] = { 'K', 'M', 'G', 'T', 'P', 'E' };
 	int base = 0;
-	while (size >= 10000) {
+	while (size >= 10000 && base < sizeof(units)-1) {
 		/* shift + round */
 		size = (size >> 10) + !!(size & (1<<9));
 		base++;
 	}
-	sprintf(buf, "%lu %cB", (long)size, units[base]);
+	sprintf(buf, "%u %cB", (unsigned)size, units[base]);
 
 	return buf;
 }
@@ -642,11 +642,19 @@ enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *mdev, enum dds_
 		|| prev_size	   != mdev->ldev->md.md_size_sect;
 
 	if (la_size_changed || md_moved) {
+		int err;
+
 		drbd_al_shrink(mdev); /* All extents inactive. */
 		dev_info(DEV, "Writing the whole bitmap, %s\n",
 			 la_size_changed && md_moved ? "size changed and md moved" :
 			 la_size_changed ? "size changed" : "md moved");
-		rv = drbd_bitmap_io(mdev, &drbd_bm_write, "size changed"); /* does drbd_resume_io() ! */
+		/* next line implicitly does drbd_suspend_io()+drbd_resume_io() */
+		err = drbd_bitmap_io(mdev, &drbd_bm_write,
+				"size changed", BM_LOCKED_MASK);
+		if (err) {
+			rv = dev_size_error;
+			goto out;
+		}
 		drbd_md_mark_dirty(mdev);
 	}
 
@@ -765,22 +773,21 @@ static int drbd_check_al_size(struct drbd_conf *mdev)
 	return 0;
 }
 
-void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_seg_s) __must_hold(local)
+void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_bio_size) __must_hold(local)
 {
 	struct request_queue * const q = mdev->rq_queue;
 	struct request_queue * const b = mdev->ldev->backing_bdev->bd_disk->queue;
 	int max_segments = mdev->ldev->dc.max_bio_bvecs;
+	int max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
 
-	max_seg_s = min(queue_max_sectors(b) * queue_logical_block_size(b), max_seg_s);
-
-	blk_queue_max_hw_sectors(q, max_seg_s >> 9);
-	blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
-	blk_queue_max_segment_size(q, max_seg_s);
 	blk_queue_logical_block_size(q, 512);
-	blk_queue_segment_boundary(q, PAGE_SIZE-1);
-	blk_stack_limits(&q->limits, &b->limits, 0);
+	blk_queue_max_hw_sectors(q, max_hw_sectors);
+	/* This is the workaround for "bio would need to, but cannot, be split" */
+	blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
+	blk_queue_segment_boundary(q, PAGE_CACHE_SIZE-1);
+	blk_queue_stack_limits(q, b);
 
-	dev_info(DEV, "max_segment_size ( = BIO size ) = %u\n", queue_max_segment_size(q));
+	dev_info(DEV, "max BIO size = %u\n", queue_max_hw_sectors(q) << 9);
 
 	if (q->backing_dev_info.ra_pages != b->backing_dev_info.ra_pages) {
 		dev_info(DEV, "Adjusting my ra_pages to backing device's (%lu -> %lu)\n",
@@ -850,7 +857,7 @@ static void drbd_suspend_al(struct drbd_conf *mdev)
 static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 			     struct drbd_nl_cfg_reply *reply)
 {
-	enum drbd_ret_codes retcode;
+	enum drbd_ret_code retcode;
 	enum determine_dev_size dd;
 	sector_t max_possible_sectors;
 	sector_t min_md_device_sectors;
@@ -858,8 +865,8 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 	struct block_device *bdev;
 	struct lru_cache *resync_lru = NULL;
 	union drbd_state ns, os;
-	unsigned int max_seg_s;
-	int rv;
+	unsigned int max_bio_size;
+	enum drbd_state_rv rv;
 	int cp_discovered = 0;
 	int logical_block_size;
 
@@ -1005,9 +1012,10 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 	/* and for any other previously queued work */
 	drbd_flush_workqueue(mdev);
 
-	retcode = _drbd_request_state(mdev, NS(disk, D_ATTACHING), CS_VERBOSE);
+	rv = _drbd_request_state(mdev, NS(disk, D_ATTACHING), CS_VERBOSE);
+	retcode = rv;  /* FIXME: Type mismatch. */
 	drbd_resume_io(mdev);
-	if (retcode < SS_SUCCESS)
+	if (rv < SS_SUCCESS)
 		goto fail;
 
 	if (!get_ldev_if_state(mdev, D_ATTACHING))
@@ -1109,20 +1117,20 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 	mdev->read_cnt = 0;
 	mdev->writ_cnt = 0;
 
-	max_seg_s = DRBD_MAX_SEGMENT_SIZE;
+	max_bio_size = DRBD_MAX_BIO_SIZE;
 	if (mdev->state.conn == C_CONNECTED) {
 		/* We are Primary, Connected, and now attach a new local
 		 * backing store. We must not increase the user visible maximum
 		 * bio size on this device to something the peer may not be
 		 * able to handle. */
 		if (mdev->agreed_pro_version < 94)
-			max_seg_s = queue_max_segment_size(mdev->rq_queue);
+			max_bio_size = queue_max_hw_sectors(mdev->rq_queue) << 9;
 		else if (mdev->agreed_pro_version == 94)
-			max_seg_s = DRBD_MAX_SIZE_H80_PACKET;
+			max_bio_size = DRBD_MAX_SIZE_H80_PACKET;
 		/* else: drbd 8.3.9 and later, stay with default */
 	}
 
-	drbd_setup_queue_param(mdev, max_seg_s);
+	drbd_setup_queue_param(mdev, max_bio_size);
 
 	/* If I am currently not R_PRIMARY,
 	 * but meta data primary indicator is set,
@@ -1154,12 +1162,14 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 	if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
 		dev_info(DEV, "Assuming that all blocks are out of sync "
 		     "(aka FullSync)\n");
-		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from attaching")) {
+		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write,
+			"set_n_write from attaching", BM_LOCKED_MASK)) {
 			retcode = ERR_IO_MD_DISK;
 			goto force_diskless_dec;
 		}
 	} else {
-		if (drbd_bitmap_io(mdev, &drbd_bm_read, "read from attaching") < 0) {
+		if (drbd_bitmap_io(mdev, &drbd_bm_read,
+			"read from attaching", BM_LOCKED_MASK) < 0) {
 			retcode = ERR_IO_MD_DISK;
 			goto force_diskless_dec;
 		}
@@ -1167,7 +1177,11 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 
 	if (cp_discovered) {
 		drbd_al_apply_to_bm(mdev);
-		drbd_al_to_on_disk_bm(mdev);
+		if (drbd_bitmap_io(mdev, &drbd_bm_write,
+			"crashed primary apply AL", BM_LOCKED_MASK)) {
+			retcode = ERR_IO_MD_DISK;
+			goto force_diskless_dec;
+		}
 	}
 
 	if (_drbd_bm_total_weight(mdev) == drbd_bm_bits(mdev))
@@ -1279,7 +1293,7 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 			    struct drbd_nl_cfg_reply *reply)
 {
 	int i, ns;
-	enum drbd_ret_codes retcode;
+	enum drbd_ret_code retcode;
 	struct net_conf *new_conf = NULL;
 	struct crypto_hash *tfm = NULL;
 	struct crypto_hash *integrity_w_tfm = NULL;
@@ -1324,6 +1338,8 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 	new_conf->wire_protocol    = DRBD_PROT_C;
 	new_conf->ping_timeo	   = DRBD_PING_TIMEO_DEF;
 	new_conf->rr_conflict	   = DRBD_RR_CONFLICT_DEF;
+	new_conf->on_congestion    = DRBD_ON_CONGESTION_DEF;
+	new_conf->cong_extents     = DRBD_CONG_EXTENTS_DEF;
 
 	if (!net_conf_from_tags(mdev, nlp->tag_list, new_conf)) {
 		retcode = ERR_MANDATORY_TAG;
@@ -1345,6 +1361,11 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 		}
 	}
 
+	if (new_conf->on_congestion != OC_BLOCK && new_conf->wire_protocol != DRBD_PROT_A) {
+		retcode = ERR_CONG_NOT_PROTO_A;
+		goto fail;
+	}
+
 	if (mdev->state.role == R_PRIMARY && new_conf->want_lose) {
 		retcode = ERR_DISCARD;
 		goto fail;
@@ -1525,6 +1546,21 @@ static int drbd_nl_disconnect(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nl
 			      struct drbd_nl_cfg_reply *reply)
 {
 	int retcode;
+	struct disconnect dc;
+
+	memset(&dc, 0, sizeof(struct disconnect));
+	if (!disconnect_from_tags(mdev, nlp->tag_list, &dc)) {
+		retcode = ERR_MANDATORY_TAG;
+		goto fail;
+	}
+
+	if (dc.force) {
+		spin_lock_irq(&mdev->req_lock);
+		if (mdev->state.conn >= C_WF_CONNECTION)
+			_drbd_set_state(_NS(mdev, conn, C_DISCONNECTING), CS_HARD, NULL);
+		spin_unlock_irq(&mdev->req_lock);
+		goto done;
+	}
 
 	retcode = _drbd_request_state(mdev, NS(conn, C_DISCONNECTING), CS_ORDERED);
 
@@ -1842,6 +1878,10 @@ static int drbd_nl_invalidate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nl
 {
 	int retcode;
 
+	/* If there is still bitmap IO pending, probably because of a previous
+	 * resync just being finished, wait for it before requesting a new resync. */
+	wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
+
 	retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T), CS_ORDERED);
 
 	if (retcode < SS_SUCCESS && retcode != SS_NEED_CONNECTION)
@@ -1877,6 +1917,10 @@ static int drbd_nl_invalidate_peer(struct drbd_conf *mdev, struct drbd_nl_cfg_re
 {
 	int retcode;
 
+	/* If there is still bitmap IO pending, probably because of a previous
+	 * resync just being finished, wait for it before requesting a new resync. */
+	wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
+
 	retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_S), CS_ORDERED);
 
 	if (retcode < SS_SUCCESS) {
@@ -1885,9 +1929,9 @@ static int drbd_nl_invalidate_peer(struct drbd_conf *mdev, struct drbd_nl_cfg_re
 			   into a full resync. */
 			retcode = drbd_request_state(mdev, NS(pdsk, D_INCONSISTENT));
 			if (retcode >= SS_SUCCESS) {
-				/* open coded drbd_bitmap_io() */
 				if (drbd_bitmap_io(mdev, &drbd_bmio_set_susp_al,
-						   "set_n_write from invalidate_peer"))
+					"set_n_write from invalidate_peer",
+					BM_LOCKED_SET_ALLOWED))
 					retcode = ERR_IO_MD_DISK;
 			}
 		} else
@@ -1914,9 +1958,17 @@ static int drbd_nl_resume_sync(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
 			       struct drbd_nl_cfg_reply *reply)
 {
 	int retcode = NO_ERROR;
+	union drbd_state s;
 
-	if (drbd_request_state(mdev, NS(user_isp, 0)) == SS_NOTHING_TO_DO)
-		retcode = ERR_PAUSE_IS_CLEAR;
+	if (drbd_request_state(mdev, NS(user_isp, 0)) == SS_NOTHING_TO_DO) {
+		s = mdev->state;
+		if (s.conn == C_PAUSED_SYNC_S || s.conn == C_PAUSED_SYNC_T) {
+			retcode = s.aftr_isp ? ERR_PIC_AFTER_DEP :
+				  s.peer_isp ? ERR_PIC_PEER_DEP : ERR_PAUSE_IS_CLEAR;
+		} else {
+			retcode = ERR_PAUSE_IS_CLEAR;
+		}
+	}
 
 	reply->ret_code = retcode;
 	return 0;
@@ -2054,6 +2106,11 @@ static int drbd_nl_start_ov(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 		reply->ret_code = ERR_MANDATORY_TAG;
 		return 0;
 	}
+
+	/* If there is still bitmap IO pending, e.g. previous resync or verify
+	 * just being finished, wait for it before requesting a new resync. */
+	wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
+
 	/* w_make_ov_request expects position to be aligned */
 	mdev->ov_start_sector = args.start_sector & ~BM_SECT_PER_BIT;
 	reply->ret_code = drbd_request_state(mdev,NS(conn,C_VERIFY_S));
@@ -2097,7 +2154,8 @@ static int drbd_nl_new_c_uuid(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nl
 	drbd_uuid_new_current(mdev); /* New current, previous to UI_BITMAP */
 
 	if (args.clear_bm) {
-		err = drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write, "clear_n_write from new_c_uuid");
+		err = drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write,
+			"clear_n_write from new_c_uuid", BM_LOCKED_MASK);
 		if (err) {
 			dev_err(DEV, "Writing bitmap failed with %d\n",err);
 			retcode = ERR_IO_MD_DISK;
@@ -2105,6 +2163,7 @@ static int drbd_nl_new_c_uuid(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nl
 		if (skip_initial_sync) {
 			drbd_send_uuids_skip_initial_sync(mdev);
 			_drbd_uuid_set(mdev, UI_BITMAP, 0);
+			drbd_print_uuids(mdev, "cleared bitmap UUID");
 			spin_lock_irq(&mdev->req_lock);
 			_drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
 					CS_VERBOSE, NULL);
@@ -2189,7 +2248,8 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
 		goto fail;
 	}
 
-	if (nlp->packet_type >= P_nl_after_last_packet) {
+	if (nlp->packet_type >= P_nl_after_last_packet ||
+	    nlp->packet_type == P_return_code_only) {
 		retcode = ERR_PACKET_NR;
 		goto fail;
 	}
@@ -2205,7 +2265,7 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
 	reply_size += cm->reply_body_size;
 
 	/* allocation not in the IO path, cqueue thread context */
-	cn_reply = kmalloc(reply_size, GFP_KERNEL);
+	cn_reply = kzalloc(reply_size, GFP_KERNEL);
 	if (!cn_reply) {
 		retcode = ERR_NOMEM;
 		goto fail;
@@ -2213,7 +2273,7 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
 	reply = (struct drbd_nl_cfg_reply *) cn_reply->data;
 
 	reply->packet_type =
-		cm->reply_body_size ? nlp->packet_type : P_nl_after_last_packet;
+		cm->reply_body_size ? nlp->packet_type : P_return_code_only;
 	reply->minor = nlp->drbd_minor;
 	reply->ret_code = NO_ERROR; /* Might by modified by cm->function. */
 	/* reply->tag_list; might be modified by cm->function. */
@@ -2376,7 +2436,7 @@ void drbd_bcast_ee(struct drbd_conf *mdev,
 	/* receiver thread context, which is not in the writeout path (of this node),
 	 * but may be in the writeout path of the _other_ node.
 	 * GFP_NOIO to avoid potential "distributed deadlock". */
-	cn_reply = kmalloc(
+	cn_reply = kzalloc(
 		sizeof(struct cn_msg)+
 		sizeof(struct drbd_nl_cfg_reply)+
 		sizeof(struct dump_ee_tag_len_struct)+
@@ -2398,10 +2458,11 @@ void drbd_bcast_ee(struct drbd_conf *mdev,
 	tl = tl_add_int(tl, T_ee_sector, &e->sector);
 	tl = tl_add_int(tl, T_ee_block_id, &e->block_id);
 
+	/* dump the first 32k */
+	len = min_t(unsigned, e->size, 32 << 10);
 	put_unaligned(T_ee_data, tl++);
-	put_unaligned(e->size, tl++);
+	put_unaligned(len, tl++);
 
-	len = e->size;
 	page = e->pages;
 	page_chain_for_each(page) {
 		void *d = kmap_atomic(page, KM_USER0);
@@ -2410,6 +2471,8 @@ void drbd_bcast_ee(struct drbd_conf *mdev,
 		kunmap_atomic(d, KM_USER0);
 		tl = (unsigned short*)((char*)tl + l);
 		len -= l;
+		if (len == 0)
+			break;
 	}
 	put_unaligned(TT_END, tl++); /* Close the tag list */
 
@@ -2508,6 +2571,7 @@ void drbd_nl_send_reply(struct cn_msg *req, int ret_code)
 		(struct drbd_nl_cfg_reply *)cn_reply->data;
 	int rr;
 
+	memset(buffer, 0, sizeof(buffer));
 	cn_reply->id = req->id;
 
 	cn_reply->seq = req->seq;
@@ -2515,6 +2579,7 @@ void drbd_nl_send_reply(struct cn_msg *req, int ret_code)
 	cn_reply->len = sizeof(struct drbd_nl_cfg_reply);
 	cn_reply->flags = 0;
 
+	reply->packet_type = P_return_code_only;
 	reply->minor = ((struct drbd_nl_cfg_req *)req->data)->drbd_minor;
 	reply->ret_code = ret_code;
 
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
index 7e6ac307e2d..2959cdfb77f 100644
--- a/drivers/block/drbd/drbd_proc.c
+++ b/drivers/block/drbd/drbd_proc.c
@@ -34,6 +34,7 @@
 #include "drbd_int.h"
 
 static int drbd_proc_open(struct inode *inode, struct file *file);
+static int drbd_proc_release(struct inode *inode, struct file *file);
 
 
 struct proc_dir_entry *drbd_proc;
@@ -42,9 +43,22 @@ const struct file_operations drbd_proc_fops = {
 	.open		= drbd_proc_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= single_release,
+	.release	= drbd_proc_release,
 };
 
+void seq_printf_with_thousands_grouping(struct seq_file *seq, long v)
+{
+	/* v is in kB/sec. We don't expect TiByte/sec yet. */
+	if (unlikely(v >= 1000000)) {
+		/* cool: > GiByte/s */
+		seq_printf(seq, "%ld,", v / 1000000);
+		v /= 1000000;
+		seq_printf(seq, "%03ld,%03ld", v/1000, v % 1000);
+	} else if (likely(v >= 1000))
+		seq_printf(seq, "%ld,%03ld", v/1000, v % 1000);
+	else
+		seq_printf(seq, "%ld", v);
+}
 
 /*lge
  * progress bars shamelessly adapted from driver/md/md.c
@@ -71,10 +85,15 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 		seq_printf(seq, ".");
 	seq_printf(seq, "] ");
 
-	seq_printf(seq, "sync'ed:%3u.%u%% ", res / 10, res % 10);
-	/* if more than 1 GB display in MB */
-	if (mdev->rs_total > 0x100000L)
-		seq_printf(seq, "(%lu/%lu)M\n\t",
+	if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
+		seq_printf(seq, "verified:");
+	else
+		seq_printf(seq, "sync'ed:");
+	seq_printf(seq, "%3u.%u%% ", res / 10, res % 10);
+
+	/* if more than a few GB, display in MB */
+	if (mdev->rs_total > (4UL << (30 - BM_BLOCK_SHIFT)))
+		seq_printf(seq, "(%lu/%lu)M",
 			    (unsigned long) Bit2KB(rs_left >> 10),
 			    (unsigned long) Bit2KB(mdev->rs_total >> 10));
 	else
@@ -94,6 +113,7 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	/* Rolling marks. last_mark+1 may just now be modified.  last_mark+2 is
 	 * at least (DRBD_SYNC_MARKS-2)*DRBD_SYNC_MARK_STEP old, and has at
 	 * least DRBD_SYNC_MARK_STEP time before it will be modified. */
+	/* ------------------------ ~18s average ------------------------ */
 	i = (mdev->rs_last_mark + 2) % DRBD_SYNC_MARKS;
 	dt = (jiffies - mdev->rs_mark_time[i]) / HZ;
 	if (dt > (DRBD_SYNC_MARK_STEP * DRBD_SYNC_MARKS))
@@ -107,14 +127,24 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	seq_printf(seq, "finish: %lu:%02lu:%02lu",
 		rt / 3600, (rt % 3600) / 60, rt % 60);
 
-	/* current speed average over (SYNC_MARKS * SYNC_MARK_STEP) jiffies */
 	dbdt = Bit2KB(db/dt);
-	if (dbdt > 1000)
-		seq_printf(seq, " speed: %ld,%03ld",
-			dbdt/1000, dbdt % 1000);
-	else
-		seq_printf(seq, " speed: %ld", dbdt);
+	seq_printf(seq, " speed: ");
+	seq_printf_with_thousands_grouping(seq, dbdt);
+	seq_printf(seq, " (");
+	/* ------------------------- ~3s average ------------------------ */
+	if (proc_details >= 1) {
+		/* this is what drbd_rs_should_slow_down() uses */
+		i = (mdev->rs_last_mark + DRBD_SYNC_MARKS-1) % DRBD_SYNC_MARKS;
+		dt = (jiffies - mdev->rs_mark_time[i]) / HZ;
+		if (!dt)
+			dt++;
+		db = mdev->rs_mark_left[i] - rs_left;
+		dbdt = Bit2KB(db/dt);
+		seq_printf_with_thousands_grouping(seq, dbdt);
+		seq_printf(seq, " -- ");
+	}
 
+	/* --------------------- long term average ---------------------- */
 	/* mean speed since syncer started
 	 * we do account for PausedSync periods */
 	dt = (jiffies - mdev->rs_start - mdev->rs_paused) / HZ;
@@ -122,20 +152,34 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 		dt = 1;
 	db = mdev->rs_total - rs_left;
 	dbdt = Bit2KB(db/dt);
-	if (dbdt > 1000)
-		seq_printf(seq, " (%ld,%03ld)",
-			dbdt/1000, dbdt % 1000);
-	else
-		seq_printf(seq, " (%ld)", dbdt);
+	seq_printf_with_thousands_grouping(seq, dbdt);
+	seq_printf(seq, ")");
 
-	if (mdev->state.conn == C_SYNC_TARGET) {
-		if (mdev->c_sync_rate > 1000)
-			seq_printf(seq, " want: %d,%03d",
-				   mdev->c_sync_rate / 1000, mdev->c_sync_rate % 1000);
-		else
-			seq_printf(seq, " want: %d", mdev->c_sync_rate);
+	if (mdev->state.conn == C_SYNC_TARGET ||
+	    mdev->state.conn == C_VERIFY_S) {
+		seq_printf(seq, " want: ");
+		seq_printf_with_thousands_grouping(seq, mdev->c_sync_rate);
 	}
 	seq_printf(seq, " K/sec%s\n", stalled ? " (stalled)" : "");
+
+	if (proc_details >= 1) {
+		/* 64 bit:
+		 * we convert to sectors in the display below. */
+		unsigned long bm_bits = drbd_bm_bits(mdev);
+		unsigned long bit_pos;
+		if (mdev->state.conn == C_VERIFY_S ||
+		    mdev->state.conn == C_VERIFY_T)
+			bit_pos = bm_bits - mdev->ov_left;
+		else
+			bit_pos = mdev->bm_resync_fo;
+		/* Total sectors may be slightly off for oddly
+		 * sized devices. So what. */
+		seq_printf(seq,
+			"\t%3d%% sector pos: %llu/%llu\n",
+			(int)(bit_pos / (bm_bits/100+1)),
+			(unsigned long long)bit_pos * BM_SECT_PER_BIT,
+			(unsigned long long)bm_bits * BM_SECT_PER_BIT);
+	}
 }
 
 static void resync_dump_detail(struct seq_file *seq, struct lc_element *e)
@@ -232,20 +276,16 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
 			   mdev->epochs,
 			   write_ordering_chars[mdev->write_ordering]
 			);
-			seq_printf(seq, " oos:%lu\n",
-				   Bit2KB(drbd_bm_total_weight(mdev)));
+			seq_printf(seq, " oos:%llu\n",
+				   Bit2KB((unsigned long long)
+					   drbd_bm_total_weight(mdev)));
 		}
 		if (mdev->state.conn == C_SYNC_SOURCE ||
-		    mdev->state.conn == C_SYNC_TARGET)
+		    mdev->state.conn == C_SYNC_TARGET ||
+		    mdev->state.conn == C_VERIFY_S ||
+		    mdev->state.conn == C_VERIFY_T)
 			drbd_syncer_progress(mdev, seq);
 
-		if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
-			seq_printf(seq, "\t%3d%%      %lu/%lu\n",
-				   (int)((mdev->rs_total-mdev->ov_left) /
-					 (mdev->rs_total/100+1)),
-				   mdev->rs_total - mdev->ov_left,
-				   mdev->rs_total);
-
 		if (proc_details >= 1 && get_ldev_if_state(mdev, D_FAILED)) {
 			lc_seq_printf_stats(seq, mdev->resync);
 			lc_seq_printf_stats(seq, mdev->act_log);
@@ -265,7 +305,15 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
 
 static int drbd_proc_open(struct inode *inode, struct file *file)
 {
-	return single_open(file, drbd_seq_show, PDE(inode)->data);
+	if (try_module_get(THIS_MODULE))
+		return single_open(file, drbd_seq_show, PDE(inode)->data);
+	return -ENODEV;
+}
+
+static int drbd_proc_release(struct inode *inode, struct file *file)
+{
+	module_put(THIS_MODULE);
+	return single_release(inode, file);
 }
 
 /* PROC FS stuff end */
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 24487d4fb20..fd26666c0b0 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -187,15 +187,6 @@ static struct page *drbd_pp_first_pages_or_try_alloc(struct drbd_conf *mdev, int
 	return NULL;
 }
 
-/* kick lower level device, if we have more than (arbitrary number)
- * reference counts on it, which typically are locally submitted io
- * requests.  don't use unacked_cnt, so we speed up proto A and B, too. */
-static void maybe_kick_lo(struct drbd_conf *mdev)
-{
-	if (atomic_read(&mdev->local_cnt) >= mdev->net_conf->unplug_watermark)
-		drbd_kick_lo(mdev);
-}
-
 static void reclaim_net_ee(struct drbd_conf *mdev, struct list_head *to_be_freed)
 {
 	struct drbd_epoch_entry *e;
@@ -219,7 +210,6 @@ static void drbd_kick_lo_and_reclaim_net(struct drbd_conf *mdev)
 	LIST_HEAD(reclaimed);
 	struct drbd_epoch_entry *e, *t;
 
-	maybe_kick_lo(mdev);
 	spin_lock_irq(&mdev->req_lock);
 	reclaim_net_ee(mdev, &reclaimed);
 	spin_unlock_irq(&mdev->req_lock);
@@ -287,7 +277,7 @@ static void drbd_pp_free(struct drbd_conf *mdev, struct page *page, int is_net)
 	atomic_t *a = is_net ? &mdev->pp_in_use_by_net : &mdev->pp_in_use;
 	int i;
 
-	if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count)
+	if (drbd_pp_vacant > (DRBD_MAX_BIO_SIZE/PAGE_SIZE)*minor_count)
 		i = page_chain_free(page);
 	else {
 		struct page *tmp;
@@ -329,7 +319,7 @@ struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
 	struct page *page;
 	unsigned nr_pages = (data_size + PAGE_SIZE -1) >> PAGE_SHIFT;
 
-	if (FAULT_ACTIVE(mdev, DRBD_FAULT_AL_EE))
+	if (drbd_insert_fault(mdev, DRBD_FAULT_AL_EE))
 		return NULL;
 
 	e = mempool_alloc(drbd_ee_mempool, gfp_mask & ~__GFP_HIGHMEM);
@@ -436,8 +426,7 @@ void _drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
 	while (!list_empty(head)) {
 		prepare_to_wait(&mdev->ee_wait, &wait, TASK_UNINTERRUPTIBLE);
 		spin_unlock_irq(&mdev->req_lock);
-		drbd_kick_lo(mdev);
-		schedule();
+		io_schedule();
 		finish_wait(&mdev->ee_wait, &wait);
 		spin_lock_irq(&mdev->req_lock);
 	}
@@ -736,16 +725,16 @@ static int drbd_socket_okay(struct drbd_conf *mdev, struct socket **sock)
 	char tb[4];
 
 	if (!*sock)
-		return FALSE;
+		return false;
 
 	rr = drbd_recv_short(mdev, *sock, tb, 4, MSG_DONTWAIT | MSG_PEEK);
 
 	if (rr > 0 || rr == -EAGAIN) {
-		return TRUE;
+		return true;
 	} else {
 		sock_release(*sock);
 		*sock = NULL;
-		return FALSE;
+		return false;
 	}
 }
 
@@ -779,8 +768,7 @@ static int drbd_connect(struct drbd_conf *mdev)
 			if (s || ++try >= 3)
 				break;
 			/* give the other side time to call bind() & listen() */
-			__set_current_state(TASK_INTERRUPTIBLE);
-			schedule_timeout(HZ / 10);
+			schedule_timeout_interruptible(HZ / 10);
 		}
 
 		if (s) {
@@ -799,8 +787,7 @@ static int drbd_connect(struct drbd_conf *mdev)
 		}
 
 		if (sock && msock) {
-			__set_current_state(TASK_INTERRUPTIBLE);
-			schedule_timeout(HZ / 10);
+			schedule_timeout_interruptible(HZ / 10);
 			ok = drbd_socket_okay(mdev, &sock);
 			ok = drbd_socket_okay(mdev, &msock) && ok;
 			if (ok)
@@ -875,7 +862,7 @@ retry:
 	msock->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
 
 	/* we don't want delays.
-	 * we use TCP_CORK where apropriate, though */
+	 * we use TCP_CORK where appropriate, though */
 	drbd_tcp_nodelay(sock);
 	drbd_tcp_nodelay(msock);
 
@@ -917,7 +904,7 @@ retry:
 		put_ldev(mdev);
 	}
 
-	if (!drbd_send_protocol(mdev))
+	if (drbd_send_protocol(mdev) == -1)
 		return -1;
 	drbd_send_sync_param(mdev, &mdev->sync_conf);
 	drbd_send_sizes(mdev, 0, 0);
@@ -925,6 +912,7 @@ retry:
 	drbd_send_state(mdev);
 	clear_bit(USE_DEGR_WFC_T, &mdev->flags);
 	clear_bit(RESIZE_PENDING, &mdev->flags);
+	mod_timer(&mdev->request_timer, jiffies + HZ); /* just start it here. */
 
 	return 1;
 
@@ -943,8 +931,9 @@ static int drbd_recv_header(struct drbd_conf *mdev, enum drbd_packets *cmd, unsi
 
 	r = drbd_recv(mdev, h, sizeof(*h));
 	if (unlikely(r != sizeof(*h))) {
-		dev_err(DEV, "short read expecting header on sock: r=%d\n", r);
-		return FALSE;
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read expecting header on sock: r=%d\n", r);
+		return false;
 	}
 
 	if (likely(h->h80.magic == BE_DRBD_MAGIC)) {
@@ -958,11 +947,11 @@ static int drbd_recv_header(struct drbd_conf *mdev, enum drbd_packets *cmd, unsi
 		    be32_to_cpu(h->h80.magic),
 		    be16_to_cpu(h->h80.command),
 		    be16_to_cpu(h->h80.length));
-		return FALSE;
+		return false;
 	}
 	mdev->last_received = jiffies;
 
-	return TRUE;
+	return true;
 }
 
 static void drbd_flush(struct drbd_conf *mdev)
@@ -1085,6 +1074,16 @@ void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo)
  * @mdev:	DRBD device.
  * @e:		epoch entry
  * @rw:		flag field, see bio->bi_rw
+ *
+ * May spread the pages to multiple bios,
+ * depending on bio_add_page restrictions.
+ *
+ * Returns 0 if all bios have been submitted,
+ * -ENOMEM if we could not allocate enough bios,
+ * -ENOSPC (any better suggestion?) if we have not been able to bio_add_page a
+ *  single page to an empty bio (which should never happen and likely indicates
+ *  that the lower level IO stack is in some way broken). This has been observed
+ *  on certain Xen deployments.
  */
 /* TODO allocate from our own bio_set. */
 int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
@@ -1097,6 +1096,7 @@ int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
 	unsigned ds = e->size;
 	unsigned n_bios = 0;
 	unsigned nr_pages = (ds + PAGE_SIZE -1) >> PAGE_SHIFT;
+	int err = -ENOMEM;
 
 	/* In most cases, we will only need one bio.  But in case the lower
 	 * level restrictions happen to be different at this offset on this
@@ -1111,8 +1111,6 @@ next_bio:
 	/* > e->sector, unless this is the first bio */
 	bio->bi_sector = sector;
 	bio->bi_bdev = mdev->ldev->backing_bdev;
-	/* we special case some flags in the multi-bio case, see below
-	 * (REQ_UNPLUG) */
 	bio->bi_rw = rw;
 	bio->bi_private = e;
 	bio->bi_end_io = drbd_endio_sec;
@@ -1124,8 +1122,17 @@ next_bio:
 	page_chain_for_each(page) {
 		unsigned len = min_t(unsigned, ds, PAGE_SIZE);
 		if (!bio_add_page(bio, page, len, 0)) {
-			/* a single page must always be possible! */
-			BUG_ON(bio->bi_vcnt == 0);
+			/* A single page must always be possible!
+			 * But in case it fails anyways,
+			 * we deal with it, and complain (below). */
+			if (bio->bi_vcnt == 0) {
+				dev_err(DEV,
+					"bio_add_page failed for len=%u, "
+					"bi_vcnt=0 (bi_sector=%llu)\n",
+					len, (unsigned long long)bio->bi_sector);
+				err = -ENOSPC;
+				goto fail;
+			}
 			goto next_bio;
 		}
 		ds -= len;
@@ -1141,13 +1148,8 @@ next_bio:
 		bios = bios->bi_next;
 		bio->bi_next = NULL;
 
-		/* strip off REQ_UNPLUG unless it is the last bio */
-		if (bios)
-			bio->bi_rw &= ~REQ_UNPLUG;
-
 		drbd_generic_make_request(mdev, fault_type, bio);
 	} while (bios);
-	maybe_kick_lo(mdev);
 	return 0;
 
 fail:
@@ -1156,7 +1158,7 @@ fail:
 		bios = bios->bi_next;
 		bio_put(bio);
 	}
-	return -ENOMEM;
+	return err;
 }
 
 static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
@@ -1167,9 +1169,6 @@ static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsign
 
 	inc_unacked(mdev);
 
-	if (mdev->net_conf->wire_protocol != DRBD_PROT_C)
-		drbd_kick_lo(mdev);
-
 	mdev->current_epoch->barrier_nr = p->barrier;
 	rv = drbd_may_finish_epoch(mdev, mdev->current_epoch, EV_GOT_BARRIER_NR);
 
@@ -1181,7 +1180,7 @@ static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsign
 	switch (mdev->write_ordering) {
 	case WO_none:
 		if (rv == FE_RECYCLED)
-			return TRUE;
+			return true;
 
 		/* receiver context, in the writeout path of the other node.
 		 * avoid potential distributed deadlock */
@@ -1209,10 +1208,10 @@ static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsign
 		D_ASSERT(atomic_read(&epoch->active) == 0);
 		D_ASSERT(epoch->flags == 0);
 
-		return TRUE;
+		return true;
 	default:
 		dev_err(DEV, "Strangeness in mdev->write_ordering %d\n", mdev->write_ordering);
-		return FALSE;
+		return false;
 	}
 
 	epoch->flags = 0;
@@ -1230,7 +1229,7 @@ static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsign
 	}
 	spin_unlock(&mdev->epoch_lock);
 
-	return TRUE;
+	return true;
 }
 
 /* used from receive_RSDataReply (recv_resync_read)
@@ -1252,21 +1251,25 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
 	if (dgs) {
 		rr = drbd_recv(mdev, dig_in, dgs);
 		if (rr != dgs) {
-			dev_warn(DEV, "short read receiving data digest: read %d expected %d\n",
-			     rr, dgs);
+			if (!signal_pending(current))
+				dev_warn(DEV,
+					"short read receiving data digest: read %d expected %d\n",
+					rr, dgs);
 			return NULL;
 		}
 	}
 
 	data_size -= dgs;
 
+	ERR_IF(data_size == 0) return NULL;
 	ERR_IF(data_size &  0x1ff) return NULL;
-	ERR_IF(data_size >  DRBD_MAX_SEGMENT_SIZE) return NULL;
+	ERR_IF(data_size >  DRBD_MAX_BIO_SIZE) return NULL;
 
 	/* even though we trust out peer,
 	 * we sometimes have to double check. */
 	if (sector + (data_size>>9) > capacity) {
-		dev_err(DEV, "capacity: %llus < sector: %llus + size: %u\n",
+		dev_err(DEV, "request from peer beyond end of local disk: "
+			"capacity: %llus < sector: %llus + size: %u\n",
 			(unsigned long long)capacity,
 			(unsigned long long)sector, data_size);
 		return NULL;
@@ -1285,15 +1288,16 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
 		unsigned len = min_t(int, ds, PAGE_SIZE);
 		data = kmap(page);
 		rr = drbd_recv(mdev, data, len);
-		if (FAULT_ACTIVE(mdev, DRBD_FAULT_RECEIVE)) {
+		if (drbd_insert_fault(mdev, DRBD_FAULT_RECEIVE)) {
 			dev_err(DEV, "Fault injection: Corrupting data on receive\n");
 			data[0] = data[0] ^ (unsigned long)-1;
 		}
 		kunmap(page);
 		if (rr != len) {
 			drbd_free_ee(mdev, e);
-			dev_warn(DEV, "short read receiving data: read %d expected %d\n",
-			     rr, len);
+			if (!signal_pending(current))
+				dev_warn(DEV, "short read receiving data: read %d expected %d\n",
+				rr, len);
 			return NULL;
 		}
 		ds -= rr;
@@ -1302,7 +1306,8 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
 	if (dgs) {
 		drbd_csum_ee(mdev, mdev->integrity_r_tfm, e, dig_vv);
 		if (memcmp(dig_in, dig_vv, dgs)) {
-			dev_err(DEV, "Digest integrity check FAILED.\n");
+			dev_err(DEV, "Digest integrity check FAILED: %llus +%u\n",
+				(unsigned long long)sector, data_size);
 			drbd_bcast_ee(mdev, "digest failed",
 					dgs, dig_in, dig_vv, e);
 			drbd_free_ee(mdev, e);
@@ -1323,7 +1328,7 @@ static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
 	void *data;
 
 	if (!data_size)
-		return TRUE;
+		return true;
 
 	page = drbd_pp_alloc(mdev, 1, 1);
 
@@ -1332,8 +1337,10 @@ static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
 		rr = drbd_recv(mdev, data, min_t(int, data_size, PAGE_SIZE));
 		if (rr != min_t(int, data_size, PAGE_SIZE)) {
 			rv = 0;
-			dev_warn(DEV, "short read receiving data: read %d expected %d\n",
-			     rr, min_t(int, data_size, PAGE_SIZE));
+			if (!signal_pending(current))
+				dev_warn(DEV,
+					"short read receiving data: read %d expected %d\n",
+					rr, min_t(int, data_size, PAGE_SIZE));
 			break;
 		}
 		data_size -= rr;
@@ -1358,8 +1365,10 @@ static int recv_dless_read(struct drbd_conf *mdev, struct drbd_request *req,
 	if (dgs) {
 		rr = drbd_recv(mdev, dig_in, dgs);
 		if (rr != dgs) {
-			dev_warn(DEV, "short read receiving data reply digest: read %d expected %d\n",
-			     rr, dgs);
+			if (!signal_pending(current))
+				dev_warn(DEV,
+					"short read receiving data reply digest: read %d expected %d\n",
+					rr, dgs);
 			return 0;
 		}
 	}
@@ -1380,9 +1389,10 @@ static int recv_dless_read(struct drbd_conf *mdev, struct drbd_request *req,
 			     expect);
 		kunmap(bvec->bv_page);
 		if (rr != expect) {
-			dev_warn(DEV, "short read receiving data reply: "
-			     "read %d expected %d\n",
-			     rr, expect);
+			if (!signal_pending(current))
+				dev_warn(DEV, "short read receiving data reply: "
+					"read %d expected %d\n",
+					rr, expect);
 			return 0;
 		}
 		data_size -= rr;
@@ -1446,11 +1456,10 @@ static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_si
 
 	atomic_add(data_size >> 9, &mdev->rs_sect_ev);
 	if (drbd_submit_ee(mdev, e, WRITE, DRBD_FAULT_RS_WR) == 0)
-		return TRUE;
+		return true;
 
-	/* drbd_submit_ee currently fails for one reason only:
-	 * not being able to allocate enough bios.
-	 * Is dropping the connection going to help? */
+	/* don't care for the reason here */
+	dev_err(DEV, "submit failed, triggering re-connect\n");
 	spin_lock_irq(&mdev->req_lock);
 	list_del(&e->w.list);
 	spin_unlock_irq(&mdev->req_lock);
@@ -1458,7 +1467,7 @@ static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_si
 	drbd_free_ee(mdev, e);
 fail:
 	put_ldev(mdev);
-	return FALSE;
+	return false;
 }
 
 static int receive_DataReply(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
@@ -1475,7 +1484,7 @@ static int receive_DataReply(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 	spin_unlock_irq(&mdev->req_lock);
 	if (unlikely(!req)) {
 		dev_err(DEV, "Got a corrupt block_id/sector pair(1).\n");
-		return FALSE;
+		return false;
 	}
 
 	/* hlist_del(&req->colision) is done in _req_may_be_done, to avoid
@@ -1632,16 +1641,15 @@ static int drbd_wait_peer_seq(struct drbd_conf *mdev, const u32 packet_seq)
 	return ret;
 }
 
-static unsigned long write_flags_to_bio(struct drbd_conf *mdev, u32 dpf)
+/* see also bio_flags_to_wire()
+ * DRBD_REQ_*, because we need to semantically map the flags to data packet
+ * flags and back. We may replicate to other kernel versions. */
+static unsigned long wire_flags_to_bio(struct drbd_conf *mdev, u32 dpf)
 {
-	if (mdev->agreed_pro_version >= 95)
-		return  (dpf & DP_RW_SYNC ? REQ_SYNC : 0) |
-			(dpf & DP_UNPLUG ? REQ_UNPLUG : 0) |
-			(dpf & DP_FUA ? REQ_FUA : 0) |
-			(dpf & DP_FLUSH ? REQ_FUA : 0) |
-			(dpf & DP_DISCARD ? REQ_DISCARD : 0);
-	else
-		return dpf & DP_RW_SYNC ? (REQ_SYNC | REQ_UNPLUG) : 0;
+	return  (dpf & DP_RW_SYNC ? REQ_SYNC : 0) |
+		(dpf & DP_FUA ? REQ_FUA : 0) |
+		(dpf & DP_FLUSH ? REQ_FLUSH : 0) |
+		(dpf & DP_DISCARD ? REQ_DISCARD : 0);
 }
 
 /* mirrored write */
@@ -1654,9 +1662,6 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 	u32 dp_flags;
 
 	if (!get_ldev(mdev)) {
-		if (__ratelimit(&drbd_ratelimit_state))
-			dev_err(DEV, "Can not write mirrored data block "
-			    "to local disk.\n");
 		spin_lock(&mdev->peer_seq_lock);
 		if (mdev->peer_seq+1 == be32_to_cpu(p->seq_num))
 			mdev->peer_seq++;
@@ -1676,23 +1681,23 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 	e = read_in_block(mdev, p->block_id, sector, data_size);
 	if (!e) {
 		put_ldev(mdev);
-		return FALSE;
+		return false;
 	}
 
 	e->w.cb = e_end_block;
 
+	dp_flags = be32_to_cpu(p->dp_flags);
+	rw |= wire_flags_to_bio(mdev, dp_flags);
+
+	if (dp_flags & DP_MAY_SET_IN_SYNC)
+		e->flags |= EE_MAY_SET_IN_SYNC;
+
 	spin_lock(&mdev->epoch_lock);
 	e->epoch = mdev->current_epoch;
 	atomic_inc(&e->epoch->epoch_size);
 	atomic_inc(&e->epoch->active);
 	spin_unlock(&mdev->epoch_lock);
 
-	dp_flags = be32_to_cpu(p->dp_flags);
-	rw |= write_flags_to_bio(mdev, dp_flags);
-
-	if (dp_flags & DP_MAY_SET_IN_SYNC)
-		e->flags |= EE_MAY_SET_IN_SYNC;
-
 	/* I'm the receiver, I do hold a net_cnt reference. */
 	if (!mdev->net_conf->two_primaries) {
 		spin_lock_irq(&mdev->req_lock);
@@ -1795,7 +1800,7 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 				put_ldev(mdev);
 				wake_asender(mdev);
 				finish_wait(&mdev->misc_wait, &wait);
-				return TRUE;
+				return true;
 			}
 
 			if (signal_pending(current)) {
@@ -1851,11 +1856,10 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 	}
 
 	if (drbd_submit_ee(mdev, e, rw, DRBD_FAULT_DT_WR) == 0)
-		return TRUE;
+		return true;
 
-	/* drbd_submit_ee currently fails for one reason only:
-	 * not being able to allocate enough bios.
-	 * Is dropping the connection going to help? */
+	/* don't care for the reason here */
+	dev_err(DEV, "submit failed, triggering re-connect\n");
 	spin_lock_irq(&mdev->req_lock);
 	list_del(&e->w.list);
 	hlist_del_init(&e->colision);
@@ -1864,12 +1868,10 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 		drbd_al_complete_io(mdev, e->sector);
 
 out_interrupted:
-	/* yes, the epoch_size now is imbalanced.
-	 * but we drop the connection anyways, so we don't have a chance to
-	 * receive a barrier... atomic_inc(&mdev->epoch_size); */
+	drbd_may_finish_epoch(mdev, e->epoch, EV_PUT + EV_CLEANUP);
 	put_ldev(mdev);
 	drbd_free_ee(mdev, e);
-	return FALSE;
+	return false;
 }
 
 /* We may throttle resync, if the lower device seems to be busy,
@@ -1883,10 +1885,11 @@ out_interrupted:
  * The current sync rate used here uses only the most recent two step marks,
  * to have a short time average so we can react faster.
  */
-int drbd_rs_should_slow_down(struct drbd_conf *mdev)
+int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector)
 {
 	struct gendisk *disk = mdev->ldev->backing_bdev->bd_contains->bd_disk;
 	unsigned long db, dt, dbdt;
+	struct lc_element *tmp;
 	int curr_events;
 	int throttle = 0;
 
@@ -1894,9 +1897,22 @@ int drbd_rs_should_slow_down(struct drbd_conf *mdev)
 	if (mdev->sync_conf.c_min_rate == 0)
 		return 0;
 
+	spin_lock_irq(&mdev->al_lock);
+	tmp = lc_find(mdev->resync, BM_SECT_TO_EXT(sector));
+	if (tmp) {
+		struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+		if (test_bit(BME_PRIORITY, &bm_ext->flags)) {
+			spin_unlock_irq(&mdev->al_lock);
+			return 0;
+		}
+		/* Do not slow down if app IO is already waiting for this extent */
+	}
+	spin_unlock_irq(&mdev->al_lock);
+
 	curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +
 		      (int)part_stat_read(&disk->part0, sectors[1]) -
 			atomic_read(&mdev->rs_sect_ev);
+
 	if (!mdev->rs_last_events || curr_events - mdev->rs_last_events > 64) {
 		unsigned long rs_left;
 		int i;
@@ -1905,8 +1921,12 @@ int drbd_rs_should_slow_down(struct drbd_conf *mdev)
 
 		/* sync speed average over the last 2*DRBD_SYNC_MARK_STEP,
 		 * approx. */
-		i = (mdev->rs_last_mark + DRBD_SYNC_MARKS-2) % DRBD_SYNC_MARKS;
-		rs_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
+		i = (mdev->rs_last_mark + DRBD_SYNC_MARKS-1) % DRBD_SYNC_MARKS;
+
+		if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
+			rs_left = mdev->ov_left;
+		else
+			rs_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
 
 		dt = ((long)jiffies - (long)mdev->rs_mark_time[i]) / HZ;
 		if (!dt)
@@ -1934,15 +1954,15 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
 	sector = be64_to_cpu(p->sector);
 	size   = be32_to_cpu(p->blksize);
 
-	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+	if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_BIO_SIZE) {
 		dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
 				(unsigned long long)sector, size);
-		return FALSE;
+		return false;
 	}
 	if (sector + (size>>9) > capacity) {
 		dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
 				(unsigned long long)sector, size);
-		return FALSE;
+		return false;
 	}
 
 	if (!get_ldev_if_state(mdev, D_UP_TO_DATE)) {
@@ -1979,7 +1999,7 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
 	e = drbd_alloc_ee(mdev, p->block_id, sector, size, GFP_NOIO);
 	if (!e) {
 		put_ldev(mdev);
-		return FALSE;
+		return false;
 	}
 
 	switch (cmd) {
@@ -1992,6 +2012,8 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
 	case P_RS_DATA_REQUEST:
 		e->w.cb = w_e_end_rsdata_req;
 		fault_type = DRBD_FAULT_RS_RD;
+		/* used in the sector offset progress display */
+		mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
 		break;
 
 	case P_OV_REPLY:
@@ -2013,7 +2035,11 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
 		if (cmd == P_CSUM_RS_REQUEST) {
 			D_ASSERT(mdev->agreed_pro_version >= 89);
 			e->w.cb = w_e_end_csum_rs_req;
+			/* used in the sector offset progress display */
+			mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
 		} else if (cmd == P_OV_REPLY) {
+			/* track progress, we may need to throttle */
+			atomic_add(size >> 9, &mdev->rs_sect_in);
 			e->w.cb = w_e_end_ov_reply;
 			dec_rs_pending(mdev);
 			/* drbd_rs_begin_io done when we sent this request,
@@ -2025,9 +2051,16 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
 	case P_OV_REQUEST:
 		if (mdev->ov_start_sector == ~(sector_t)0 &&
 		    mdev->agreed_pro_version >= 90) {
+			unsigned long now = jiffies;
+			int i;
 			mdev->ov_start_sector = sector;
 			mdev->ov_position = sector;
-			mdev->ov_left = mdev->rs_total - BM_SECT_TO_BIT(sector);
+			mdev->ov_left = drbd_bm_bits(mdev) - BM_SECT_TO_BIT(sector);
+			mdev->rs_total = mdev->ov_left;
+			for (i = 0; i < DRBD_SYNC_MARKS; i++) {
+				mdev->rs_mark_left[i] = mdev->ov_left;
+				mdev->rs_mark_time[i] = now;
+			}
 			dev_info(DEV, "Online Verify start sector: %llu\n",
 					(unsigned long long)sector);
 		}
@@ -2064,9 +2097,9 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
 	 * we would also throttle its application reads.
 	 * In that case, throttling is done on the SyncTarget only.
 	 */
-	if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev))
-		msleep(100);
-	if (drbd_rs_begin_io(mdev, e->sector))
+	if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev, sector))
+		schedule_timeout_uninterruptible(HZ/10);
+	if (drbd_rs_begin_io(mdev, sector))
 		goto out_free_e;
 
 submit_for_resync:
@@ -2079,11 +2112,10 @@ submit:
 	spin_unlock_irq(&mdev->req_lock);
 
 	if (drbd_submit_ee(mdev, e, READ, fault_type) == 0)
-		return TRUE;
+		return true;
 
-	/* drbd_submit_ee currently fails for one reason only:
-	 * not being able to allocate enough bios.
-	 * Is dropping the connection going to help? */
+	/* don't care for the reason here */
+	dev_err(DEV, "submit failed, triggering re-connect\n");
 	spin_lock_irq(&mdev->req_lock);
 	list_del(&e->w.list);
 	spin_unlock_irq(&mdev->req_lock);
@@ -2092,7 +2124,7 @@ submit:
 out_free_e:
 	put_ldev(mdev);
 	drbd_free_ee(mdev, e);
-	return FALSE;
+	return false;
 }
 
 static int drbd_asb_recover_0p(struct drbd_conf *mdev) __must_hold(local)
@@ -2169,10 +2201,7 @@ static int drbd_asb_recover_0p(struct drbd_conf *mdev) __must_hold(local)
 
 static int drbd_asb_recover_1p(struct drbd_conf *mdev) __must_hold(local)
 {
-	int self, peer, hg, rv = -100;
-
-	self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
-	peer = mdev->p_uuid[UI_BITMAP] & 1;
+	int hg, rv = -100;
 
 	switch (mdev->net_conf->after_sb_1p) {
 	case ASB_DISCARD_YOUNGER_PRI:
@@ -2199,12 +2228,14 @@ static int drbd_asb_recover_1p(struct drbd_conf *mdev) __must_hold(local)
 	case ASB_CALL_HELPER:
 		hg = drbd_asb_recover_0p(mdev);
 		if (hg == -1 && mdev->state.role == R_PRIMARY) {
-			self = drbd_set_role(mdev, R_SECONDARY, 0);
+			enum drbd_state_rv rv2;
+
+			drbd_set_role(mdev, R_SECONDARY, 0);
 			 /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
 			  * we might be here in C_WF_REPORT_PARAMS which is transient.
 			  * we do not need to wait for the after state change work either. */
-			self = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
-			if (self != SS_SUCCESS) {
+			rv2 = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+			if (rv2 != SS_SUCCESS) {
 				drbd_khelper(mdev, "pri-lost-after-sb");
 			} else {
 				dev_warn(DEV, "Successfully gave up primary role.\n");
@@ -2219,10 +2250,7 @@ static int drbd_asb_recover_1p(struct drbd_conf *mdev) __must_hold(local)
 
 static int drbd_asb_recover_2p(struct drbd_conf *mdev) __must_hold(local)
 {
-	int self, peer, hg, rv = -100;
-
-	self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
-	peer = mdev->p_uuid[UI_BITMAP] & 1;
+	int hg, rv = -100;
 
 	switch (mdev->net_conf->after_sb_2p) {
 	case ASB_DISCARD_YOUNGER_PRI:
@@ -2242,11 +2270,13 @@ static int drbd_asb_recover_2p(struct drbd_conf *mdev) __must_hold(local)
 	case ASB_CALL_HELPER:
 		hg = drbd_asb_recover_0p(mdev);
 		if (hg == -1) {
+			enum drbd_state_rv rv2;
+
 			 /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
 			  * we might be here in C_WF_REPORT_PARAMS which is transient.
 			  * we do not need to wait for the after state change work either. */
-			self = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
-			if (self != SS_SUCCESS) {
+			rv2 = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+			if (rv2 != SS_SUCCESS) {
 				drbd_khelper(mdev, "pri-lost-after-sb");
 			} else {
 				dev_warn(DEV, "Successfully gave up primary role.\n");
@@ -2285,6 +2315,8 @@ static void drbd_uuid_dump(struct drbd_conf *mdev, char *text, u64 *uuid,
    -2	C_SYNC_TARGET set BitMap
  -100	after split brain, disconnect
 -1000	unrelated data
+-1091   requires proto 91
+-1096   requires proto 96
  */
 static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(local)
 {
@@ -2314,7 +2346,7 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
 		if (mdev->p_uuid[UI_BITMAP] == (u64)0 && mdev->ldev->md.uuid[UI_BITMAP] != (u64)0) {
 
 			if (mdev->agreed_pro_version < 91)
-				return -1001;
+				return -1091;
 
 			if ((mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
 			    (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1))) {
@@ -2335,7 +2367,7 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
 		if (mdev->ldev->md.uuid[UI_BITMAP] == (u64)0 && mdev->p_uuid[UI_BITMAP] != (u64)0) {
 
 			if (mdev->agreed_pro_version < 91)
-				return -1001;
+				return -1091;
 
 			if ((mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_BITMAP] & ~((u64)1)) &&
 			    (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1))) {
@@ -2380,17 +2412,22 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
 	*rule_nr = 51;
 	peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
 	if (self == peer) {
-		self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
-		peer = mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1);
-		if (self == peer) {
+		if (mdev->agreed_pro_version < 96 ?
+		    (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) ==
+		    (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1)) :
+		    peer + UUID_NEW_BM_OFFSET == (mdev->p_uuid[UI_BITMAP] & ~((u64)1))) {
 			/* The last P_SYNC_UUID did not get though. Undo the last start of
 			   resync as sync source modifications of the peer's UUIDs. */
 
 			if (mdev->agreed_pro_version < 91)
-				return -1001;
+				return -1091;
 
 			mdev->p_uuid[UI_BITMAP] = mdev->p_uuid[UI_HISTORY_START];
 			mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_HISTORY_START + 1];
+
+			dev_info(DEV, "Did not got last syncUUID packet, corrected:\n");
+			drbd_uuid_dump(mdev, "peer", mdev->p_uuid, mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+
 			return -1;
 		}
 	}
@@ -2412,20 +2449,20 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
 	*rule_nr = 71;
 	self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
 	if (self == peer) {
-		self = mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1);
-		peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
-		if (self == peer) {
+		if (mdev->agreed_pro_version < 96 ?
+		    (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) ==
+		    (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) :
+		    self + UUID_NEW_BM_OFFSET == (mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1))) {
 			/* The last P_SYNC_UUID did not get though. Undo the last start of
 			   resync as sync source modifications of our UUIDs. */
 
 			if (mdev->agreed_pro_version < 91)
-				return -1001;
+				return -1091;
 
 			_drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_HISTORY_START]);
 			_drbd_uuid_set(mdev, UI_HISTORY_START, mdev->ldev->md.uuid[UI_HISTORY_START + 1]);
 
-			dev_info(DEV, "Undid last start of resync:\n");
-
+			dev_info(DEV, "Last syncUUID did not get through, corrected:\n");
 			drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
 				       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
 
@@ -2488,8 +2525,8 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_rol
 		dev_alert(DEV, "Unrelated data, aborting!\n");
 		return C_MASK;
 	}
-	if (hg == -1001) {
-		dev_alert(DEV, "To resolve this both sides have to support at least protocol\n");
+	if (hg < -1000) {
+		dev_alert(DEV, "To resolve this both sides have to support at least protocol %d\n", -hg - 1000);
 		return C_MASK;
 	}
 
@@ -2588,7 +2625,8 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_rol
 
 	if (abs(hg) >= 2) {
 		dev_info(DEV, "Writing the whole bitmap, full sync required after drbd_sync_handshake.\n");
-		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from sync_handshake"))
+		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from sync_handshake",
+					BM_LOCKED_SET_ALLOWED))
 			return C_MASK;
 	}
 
@@ -2682,7 +2720,7 @@ static int receive_protocol(struct drbd_conf *mdev, enum drbd_packets cmd, unsig
 		unsigned char *my_alg = mdev->net_conf->integrity_alg;
 
 		if (drbd_recv(mdev, p_integrity_alg, data_size) != data_size)
-			return FALSE;
+			return false;
 
 		p_integrity_alg[SHARED_SECRET_MAX-1] = 0;
 		if (strcmp(p_integrity_alg, my_alg)) {
@@ -2693,11 +2731,11 @@ static int receive_protocol(struct drbd_conf *mdev, enum drbd_packets cmd, unsig
 		     my_alg[0] ? my_alg : (unsigned char *)"<not-used>");
 	}
 
-	return TRUE;
+	return true;
 
 disconnect:
 	drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-	return FALSE;
+	return false;
 }
 
 /* helper function
@@ -2729,7 +2767,7 @@ struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_conf *mdev,
 
 static int receive_SyncParam(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int packet_size)
 {
-	int ok = TRUE;
+	int ok = true;
 	struct p_rs_param_95 *p = &mdev->data.rbuf.rs_param_95;
 	unsigned int header_size, data_size, exp_max_sz;
 	struct crypto_hash *verify_tfm = NULL;
@@ -2747,7 +2785,7 @@ static int receive_SyncParam(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 	if (packet_size > exp_max_sz) {
 		dev_err(DEV, "SyncParam packet too long: received %u, expected <= %u bytes\n",
 		    packet_size, exp_max_sz);
-		return FALSE;
+		return false;
 	}
 
 	if (apv <= 88) {
@@ -2767,7 +2805,7 @@ static int receive_SyncParam(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 	memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
 
 	if (drbd_recv(mdev, &p->head.payload, header_size) != header_size)
-		return FALSE;
+		return false;
 
 	mdev->sync_conf.rate	  = be32_to_cpu(p->rate);
 
@@ -2777,11 +2815,11 @@ static int receive_SyncParam(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 				dev_err(DEV, "verify-alg too long, "
 				    "peer wants %u, accepting only %u byte\n",
 						data_size, SHARED_SECRET_MAX);
-				return FALSE;
+				return false;
 			}
 
 			if (drbd_recv(mdev, p->verify_alg, data_size) != data_size)
-				return FALSE;
+				return false;
 
 			/* we expect NUL terminated string */
 			/* but just in case someone tries to be evil */
@@ -2875,7 +2913,7 @@ disconnect:
 	/* but free the verify_tfm again, if csums_tfm did not work out */
 	crypto_free_hash(verify_tfm);
 	drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-	return FALSE;
+	return false;
 }
 
 static void drbd_setup_order_type(struct drbd_conf *mdev, int peer)
@@ -2901,7 +2939,7 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 {
 	struct p_sizes *p = &mdev->data.rbuf.sizes;
 	enum determine_dev_size dd = unchanged;
-	unsigned int max_seg_s;
+	unsigned int max_bio_size;
 	sector_t p_size, p_usize, my_usize;
 	int ldsc = 0; /* local disk size changed */
 	enum dds_flags ddsf;
@@ -2912,7 +2950,7 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 	if (p_size == 0 && mdev->state.disk == D_DISKLESS) {
 		dev_err(DEV, "some backing storage is needed\n");
 		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-		return FALSE;
+		return false;
 	}
 
 	/* just store the peer's disk size for now.
@@ -2949,18 +2987,17 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
 			mdev->ldev->dc.disk_size = my_usize;
 			put_ldev(mdev);
-			return FALSE;
+			return false;
 		}
 		put_ldev(mdev);
 	}
-#undef min_not_zero
 
 	ddsf = be16_to_cpu(p->dds_flags);
 	if (get_ldev(mdev)) {
 		dd = drbd_determin_dev_size(mdev, ddsf);
 		put_ldev(mdev);
 		if (dd == dev_size_error)
-			return FALSE;
+			return false;
 		drbd_md_sync(mdev);
 	} else {
 		/* I am diskless, need to accept the peer's size. */
@@ -2974,14 +3011,14 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 		}
 
 		if (mdev->agreed_pro_version < 94)
-			max_seg_s = be32_to_cpu(p->max_segment_size);
+			max_bio_size = be32_to_cpu(p->max_bio_size);
 		else if (mdev->agreed_pro_version == 94)
-			max_seg_s = DRBD_MAX_SIZE_H80_PACKET;
+			max_bio_size = DRBD_MAX_SIZE_H80_PACKET;
 		else /* drbd 8.3.8 onwards */
-			max_seg_s = DRBD_MAX_SEGMENT_SIZE;
+			max_bio_size = DRBD_MAX_BIO_SIZE;
 
-		if (max_seg_s != queue_max_segment_size(mdev->rq_queue))
-			drbd_setup_queue_param(mdev, max_seg_s);
+		if (max_bio_size != queue_max_hw_sectors(mdev->rq_queue) << 9)
+			drbd_setup_queue_param(mdev, max_bio_size);
 
 		drbd_setup_order_type(mdev, be16_to_cpu(p->queue_order_type));
 		put_ldev(mdev);
@@ -3007,14 +3044,14 @@ static int receive_sizes(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 		}
 	}
 
-	return TRUE;
+	return true;
 }
 
 static int receive_uuids(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
 {
 	struct p_uuids *p = &mdev->data.rbuf.uuids;
 	u64 *p_uuid;
-	int i;
+	int i, updated_uuids = 0;
 
 	p_uuid = kmalloc(sizeof(u64)*UI_EXTENDED_SIZE, GFP_NOIO);
 
@@ -3031,7 +3068,7 @@ static int receive_uuids(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 		dev_err(DEV, "Can only connect to data with current UUID=%016llX\n",
 		    (unsigned long long)mdev->ed_uuid);
 		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-		return FALSE;
+		return false;
 	}
 
 	if (get_ldev(mdev)) {
@@ -3043,19 +3080,21 @@ static int receive_uuids(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 		if (skip_initial_sync) {
 			dev_info(DEV, "Accepted new current UUID, preparing to skip initial sync\n");
 			drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write,
-					"clear_n_write from receive_uuids");
+					"clear_n_write from receive_uuids",
+					BM_LOCKED_TEST_ALLOWED);
 			_drbd_uuid_set(mdev, UI_CURRENT, p_uuid[UI_CURRENT]);
 			_drbd_uuid_set(mdev, UI_BITMAP, 0);
 			_drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
 					CS_VERBOSE, NULL);
 			drbd_md_sync(mdev);
+			updated_uuids = 1;
 		}
 		put_ldev(mdev);
 	} else if (mdev->state.disk < D_INCONSISTENT &&
 		   mdev->state.role == R_PRIMARY) {
 		/* I am a diskless primary, the peer just created a new current UUID
 		   for me. */
-		drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
+		updated_uuids = drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
 	}
 
 	/* Before we test for the disk state, we should wait until an eventually
@@ -3064,9 +3103,12 @@ static int receive_uuids(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 	   new disk state... */
 	wait_event(mdev->misc_wait, !test_bit(CLUSTER_ST_CHANGE, &mdev->flags));
 	if (mdev->state.conn >= C_CONNECTED && mdev->state.disk < D_INCONSISTENT)
-		drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
+		updated_uuids |= drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
 
-	return TRUE;
+	if (updated_uuids)
+		drbd_print_uuids(mdev, "receiver updated UUIDs to");
+
+	return true;
 }
 
 /**
@@ -3103,7 +3145,7 @@ static int receive_req_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 {
 	struct p_req_state *p = &mdev->data.rbuf.req_state;
 	union drbd_state mask, val;
-	int rv;
+	enum drbd_state_rv rv;
 
 	mask.i = be32_to_cpu(p->mask);
 	val.i = be32_to_cpu(p->val);
@@ -3111,7 +3153,7 @@ static int receive_req_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 	if (test_bit(DISCARD_CONCURRENT, &mdev->flags) &&
 	    test_bit(CLUSTER_ST_CHANGE, &mdev->flags)) {
 		drbd_send_sr_reply(mdev, SS_CONCURRENT_ST_CHG);
-		return TRUE;
+		return true;
 	}
 
 	mask = convert_state(mask);
@@ -3122,7 +3164,7 @@ static int receive_req_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 	drbd_send_sr_reply(mdev, rv);
 	drbd_md_sync(mdev);
 
-	return TRUE;
+	return true;
 }
 
 static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
@@ -3167,7 +3209,7 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 			 peer_state.conn == C_CONNECTED) {
 			if (drbd_bm_total_weight(mdev) <= mdev->rs_failed)
 				drbd_resync_finished(mdev);
-			return TRUE;
+			return true;
 		}
 	}
 
@@ -3183,6 +3225,9 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 	if (ns.conn == C_WF_REPORT_PARAMS)
 		ns.conn = C_CONNECTED;
 
+	if (peer_state.conn == C_AHEAD)
+		ns.conn = C_BEHIND;
+
 	if (mdev->p_uuid && peer_state.disk >= D_NEGOTIATING &&
 	    get_ldev_if_state(mdev, D_NEGOTIATING)) {
 		int cr; /* consider resync */
@@ -3217,10 +3262,10 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 				real_peer_disk = D_DISKLESS;
 			} else {
 				if (test_and_clear_bit(CONN_DRY_RUN, &mdev->flags))
-					return FALSE;
+					return false;
 				D_ASSERT(os.conn == C_WF_REPORT_PARAMS);
 				drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-				return FALSE;
+				return false;
 			}
 		}
 	}
@@ -3245,7 +3290,7 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 		drbd_uuid_new_current(mdev);
 		clear_bit(NEW_CUR_UUID, &mdev->flags);
 		drbd_force_state(mdev, NS2(conn, C_PROTOCOL_ERROR, susp, 0));
-		return FALSE;
+		return false;
 	}
 	rv = _drbd_set_state(mdev, ns, cs_flags, NULL);
 	ns = mdev->state;
@@ -3253,7 +3298,7 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 
 	if (rv < SS_SUCCESS) {
 		drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-		return FALSE;
+		return false;
 	}
 
 	if (os.conn > C_WF_REPORT_PARAMS) {
@@ -3271,7 +3316,7 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 
 	drbd_md_sync(mdev); /* update connected indicator, la_size, ... */
 
-	return TRUE;
+	return true;
 }
 
 static int receive_sync_uuid(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
@@ -3280,6 +3325,7 @@ static int receive_sync_uuid(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 
 	wait_event(mdev->misc_wait,
 		   mdev->state.conn == C_WF_SYNC_UUID ||
+		   mdev->state.conn == C_BEHIND ||
 		   mdev->state.conn < C_CONNECTED ||
 		   mdev->state.disk < D_NEGOTIATING);
 
@@ -3291,32 +3337,42 @@ static int receive_sync_uuid(struct drbd_conf *mdev, enum drbd_packets cmd, unsi
 		_drbd_uuid_set(mdev, UI_CURRENT, be64_to_cpu(p->uuid));
 		_drbd_uuid_set(mdev, UI_BITMAP, 0UL);
 
+		drbd_print_uuids(mdev, "updated sync uuid");
 		drbd_start_resync(mdev, C_SYNC_TARGET);
 
 		put_ldev(mdev);
 	} else
 		dev_err(DEV, "Ignoring SyncUUID packet!\n");
 
-	return TRUE;
+	return true;
 }
 
-enum receive_bitmap_ret { OK, DONE, FAILED };
-
-static enum receive_bitmap_ret
+/**
+ * receive_bitmap_plain
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
 receive_bitmap_plain(struct drbd_conf *mdev, unsigned int data_size,
 		     unsigned long *buffer, struct bm_xfer_ctx *c)
 {
 	unsigned num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
 	unsigned want = num_words * sizeof(long);
+	int err;
 
 	if (want != data_size) {
 		dev_err(DEV, "%s:want (%u) != data_size (%u)\n", __func__, want, data_size);
-		return FAILED;
+		return -EIO;
 	}
 	if (want == 0)
-		return DONE;
-	if (drbd_recv(mdev, buffer, want) != want)
-		return FAILED;
+		return 0;
+	err = drbd_recv(mdev, buffer, want);
+	if (err != want) {
+		if (err >= 0)
+			err = -EIO;
+		return err;
+	}
 
 	drbd_bm_merge_lel(mdev, c->word_offset, num_words, buffer);
 
@@ -3325,10 +3381,16 @@ receive_bitmap_plain(struct drbd_conf *mdev, unsigned int data_size,
 	if (c->bit_offset > c->bm_bits)
 		c->bit_offset = c->bm_bits;
 
-	return OK;
+	return 1;
 }
 
-static enum receive_bitmap_ret
+/**
+ * recv_bm_rle_bits
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
 recv_bm_rle_bits(struct drbd_conf *mdev,
 		struct p_compressed_bm *p,
 		struct bm_xfer_ctx *c)
@@ -3348,18 +3410,18 @@ recv_bm_rle_bits(struct drbd_conf *mdev,
 
 	bits = bitstream_get_bits(&bs, &look_ahead, 64);
 	if (bits < 0)
-		return FAILED;
+		return -EIO;
 
 	for (have = bits; have > 0; s += rl, toggle = !toggle) {
 		bits = vli_decode_bits(&rl, look_ahead);
 		if (bits <= 0)
-			return FAILED;
+			return -EIO;
 
 		if (toggle) {
 			e = s + rl -1;
 			if (e >= c->bm_bits) {
 				dev_err(DEV, "bitmap overflow (e:%lu) while decoding bm RLE packet\n", e);
-				return FAILED;
+				return -EIO;
 			}
 			_drbd_bm_set_bits(mdev, s, e);
 		}
@@ -3369,14 +3431,14 @@ recv_bm_rle_bits(struct drbd_conf *mdev,
 				have, bits, look_ahead,
 				(unsigned int)(bs.cur.b - p->code),
 				(unsigned int)bs.buf_len);
-			return FAILED;
+			return -EIO;
 		}
 		look_ahead >>= bits;
 		have -= bits;
 
 		bits = bitstream_get_bits(&bs, &tmp, 64 - have);
 		if (bits < 0)
-			return FAILED;
+			return -EIO;
 		look_ahead |= tmp << have;
 		have += bits;
 	}
@@ -3384,10 +3446,16 @@ recv_bm_rle_bits(struct drbd_conf *mdev,
 	c->bit_offset = s;
 	bm_xfer_ctx_bit_to_word_offset(c);
 
-	return (s == c->bm_bits) ? DONE : OK;
+	return (s != c->bm_bits);
 }
 
-static enum receive_bitmap_ret
+/**
+ * decode_bitmap_c
+ *
+ * Return 0 when done, 1 when another iteration is needed, and a negative error
+ * code upon failure.
+ */
+static int
 decode_bitmap_c(struct drbd_conf *mdev,
 		struct p_compressed_bm *p,
 		struct bm_xfer_ctx *c)
@@ -3401,7 +3469,7 @@ decode_bitmap_c(struct drbd_conf *mdev,
 
 	dev_err(DEV, "receive_bitmap_c: unknown encoding %u\n", p->encoding);
 	drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
-	return FAILED;
+	return -EIO;
 }
 
 void INFO_bm_xfer_stats(struct drbd_conf *mdev,
@@ -3450,13 +3518,13 @@ static int receive_bitmap(struct drbd_conf *mdev, enum drbd_packets cmd, unsigne
 {
 	struct bm_xfer_ctx c;
 	void *buffer;
-	enum receive_bitmap_ret ret;
-	int ok = FALSE;
+	int err;
+	int ok = false;
 	struct p_header80 *h = &mdev->data.rbuf.header.h80;
 
-	wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_bio_cnt));
-
-	drbd_bm_lock(mdev, "receive bitmap");
+	drbd_bm_lock(mdev, "receive bitmap", BM_LOCKED_SET_ALLOWED);
+	/* you are supposed to send additional out-of-sync information
+	 * if you actually set bits during this phase */
 
 	/* maybe we should use some per thread scratch page,
 	 * and allocate that during initial device creation? */
@@ -3471,9 +3539,9 @@ static int receive_bitmap(struct drbd_conf *mdev, enum drbd_packets cmd, unsigne
 		.bm_words = drbd_bm_words(mdev),
 	};
 
-	do {
+	for(;;) {
 		if (cmd == P_BITMAP) {
-			ret = receive_bitmap_plain(mdev, data_size, buffer, &c);
+			err = receive_bitmap_plain(mdev, data_size, buffer, &c);
 		} else if (cmd == P_COMPRESSED_BITMAP) {
 			/* MAYBE: sanity check that we speak proto >= 90,
 			 * and the feature is enabled! */
@@ -3490,9 +3558,9 @@ static int receive_bitmap(struct drbd_conf *mdev, enum drbd_packets cmd, unsigne
 				goto out;
 			if (data_size <= (sizeof(*p) - sizeof(p->head))) {
 				dev_err(DEV, "ReportCBitmap packet too small (l:%u)\n", data_size);
-				return FAILED;
+				goto out;
 			}
-			ret = decode_bitmap_c(mdev, p, &c);
+			err = decode_bitmap_c(mdev, p, &c);
 		} else {
 			dev_warn(DEV, "receive_bitmap: cmd neither ReportBitMap nor ReportCBitMap (is 0x%x)", cmd);
 			goto out;
@@ -3501,24 +3569,26 @@ static int receive_bitmap(struct drbd_conf *mdev, enum drbd_packets cmd, unsigne
 		c.packets[cmd == P_BITMAP]++;
 		c.bytes[cmd == P_BITMAP] += sizeof(struct p_header80) + data_size;
 
-		if (ret != OK)
+		if (err <= 0) {
+			if (err < 0)
+				goto out;
 			break;
-
+		}
 		if (!drbd_recv_header(mdev, &cmd, &data_size))
 			goto out;
-	} while (ret == OK);
-	if (ret == FAILED)
-		goto out;
+	}
 
 	INFO_bm_xfer_stats(mdev, "receive", &c);
 
 	if (mdev->state.conn == C_WF_BITMAP_T) {
+		enum drbd_state_rv rv;
+
 		ok = !drbd_send_bitmap(mdev);
 		if (!ok)
 			goto out;
 		/* Omit CS_ORDERED with this state transition to avoid deadlocks. */
-		ok = _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
-		D_ASSERT(ok == SS_SUCCESS);
+		rv = _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+		D_ASSERT(rv == SS_SUCCESS);
 	} else if (mdev->state.conn != C_WF_BITMAP_S) {
 		/* admin may have requested C_DISCONNECTING,
 		 * other threads may have noticed network errors */
@@ -3526,7 +3596,7 @@ static int receive_bitmap(struct drbd_conf *mdev, enum drbd_packets cmd, unsigne
 		    drbd_conn_str(mdev->state.conn));
 	}
 
-	ok = TRUE;
+	ok = true;
  out:
 	drbd_bm_unlock(mdev);
 	if (ok && mdev->state.conn == C_WF_BITMAP_S)
@@ -3556,14 +3626,30 @@ static int receive_skip(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 
 static int receive_UnplugRemote(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
 {
-	if (mdev->state.disk >= D_INCONSISTENT)
-		drbd_kick_lo(mdev);
-
 	/* Make sure we've acked all the TCP data associated
 	 * with the data requests being unplugged */
 	drbd_tcp_quickack(mdev->data.socket);
 
-	return TRUE;
+	return true;
+}
+
+static int receive_out_of_sync(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
+{
+	struct p_block_desc *p = &mdev->data.rbuf.block_desc;
+
+	switch (mdev->state.conn) {
+	case C_WF_SYNC_UUID:
+	case C_WF_BITMAP_T:
+	case C_BEHIND:
+			break;
+	default:
+		dev_err(DEV, "ASSERT FAILED cstate = %s, expected: WFSyncUUID|WFBitMapT|Behind\n",
+				drbd_conn_str(mdev->state.conn));
+	}
+
+	drbd_set_out_of_sync(mdev, be64_to_cpu(p->sector), be32_to_cpu(p->blksize));
+
+	return true;
 }
 
 typedef int (*drbd_cmd_handler_f)(struct drbd_conf *, enum drbd_packets cmd, unsigned int to_receive);
@@ -3596,6 +3682,7 @@ static struct data_cmd drbd_cmd_handler[] = {
 	[P_OV_REPLY]        = { 1, sizeof(struct p_block_req), receive_DataRequest },
 	[P_CSUM_RS_REQUEST] = { 1, sizeof(struct p_block_req), receive_DataRequest },
 	[P_DELAY_PROBE]     = { 0, sizeof(struct p_delay_probe93), receive_skip },
+	[P_OUT_OF_SYNC]     = { 0, sizeof(struct p_block_desc), receive_out_of_sync },
 	/* anything missing from this table is in
 	 * the asender_tbl, see get_asender_cmd */
 	[P_MAX_CMD]	    = { 0, 0, NULL },
@@ -3635,7 +3722,8 @@ static void drbdd(struct drbd_conf *mdev)
 		if (shs) {
 			rv = drbd_recv(mdev, &header->h80.payload, shs);
 			if (unlikely(rv != shs)) {
-				dev_err(DEV, "short read while reading sub header: rv=%d\n", rv);
+				if (!signal_pending(current))
+					dev_warn(DEV, "short read while reading sub header: rv=%d\n", rv);
 				goto err_out;
 			}
 		}
@@ -3707,9 +3795,6 @@ static void drbd_disconnect(struct drbd_conf *mdev)
 
 	if (mdev->state.conn == C_STANDALONE)
 		return;
-	if (mdev->state.conn >= C_WF_CONNECTION)
-		dev_err(DEV, "ASSERT FAILED cstate = %s, expected < WFConnection\n",
-				drbd_conn_str(mdev->state.conn));
 
 	/* asender does not clean up anything. it must not interfere, either */
 	drbd_thread_stop(&mdev->asender);
@@ -3738,6 +3823,8 @@ static void drbd_disconnect(struct drbd_conf *mdev)
 	atomic_set(&mdev->rs_pending_cnt, 0);
 	wake_up(&mdev->misc_wait);
 
+	del_timer(&mdev->request_timer);
+
 	/* make sure syncer is stopped and w_resume_next_sg queued */
 	del_timer_sync(&mdev->resync_timer);
 	resync_timer_fn((unsigned long)mdev);
@@ -3783,13 +3870,6 @@ static void drbd_disconnect(struct drbd_conf *mdev)
 	if (os.conn == C_DISCONNECTING) {
 		wait_event(mdev->net_cnt_wait, atomic_read(&mdev->net_cnt) == 0);
 
-		if (!is_susp(mdev->state)) {
-			/* we must not free the tl_hash
-			 * while application io is still on the fly */
-			wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_bio_cnt));
-			drbd_free_tl_hash(mdev);
-		}
-
 		crypto_free_hash(mdev->cram_hmac_tfm);
 		mdev->cram_hmac_tfm = NULL;
 
@@ -3798,6 +3878,10 @@ static void drbd_disconnect(struct drbd_conf *mdev)
 		drbd_request_state(mdev, NS(conn, C_STANDALONE));
 	}
 
+	/* serialize with bitmap writeout triggered by the state change,
+	 * if any. */
+	wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
+
 	/* tcp_close and release of sendpage pages can be deferred.  I don't
 	 * want to use SO_LINGER, because apparently it can be deferred for
 	 * more than 20 seconds (longest time I checked).
@@ -3898,7 +3982,8 @@ static int drbd_do_handshake(struct drbd_conf *mdev)
 	rv = drbd_recv(mdev, &p->head.payload, expect);
 
 	if (rv != expect) {
-		dev_err(DEV, "short read receiving handshake packet: l=%u\n", rv);
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read receiving handshake packet: l=%u\n", rv);
 		return 0;
 	}
 
@@ -4000,7 +4085,8 @@ static int drbd_do_auth(struct drbd_conf *mdev)
 	rv = drbd_recv(mdev, peers_ch, length);
 
 	if (rv != length) {
-		dev_err(DEV, "short read AuthChallenge: l=%u\n", rv);
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read AuthChallenge: l=%u\n", rv);
 		rv = 0;
 		goto fail;
 	}
@@ -4047,7 +4133,8 @@ static int drbd_do_auth(struct drbd_conf *mdev)
 	rv = drbd_recv(mdev, response , resp_size);
 
 	if (rv != resp_size) {
-		dev_err(DEV, "short read receiving AuthResponse: l=%u\n", rv);
+		if (!signal_pending(current))
+			dev_warn(DEV, "short read receiving AuthResponse: l=%u\n", rv);
 		rv = 0;
 		goto fail;
 	}
@@ -4099,8 +4186,7 @@ int drbdd_init(struct drbd_thread *thi)
 		h = drbd_connect(mdev);
 		if (h == 0) {
 			drbd_disconnect(mdev);
-			__set_current_state(TASK_INTERRUPTIBLE);
-			schedule_timeout(HZ);
+			schedule_timeout_interruptible(HZ);
 		}
 		if (h == -1) {
 			dev_warn(DEV, "Discarding network configuration.\n");
@@ -4138,7 +4224,7 @@ static int got_RqSReply(struct drbd_conf *mdev, struct p_header80 *h)
 	}
 	wake_up(&mdev->state_wait);
 
-	return TRUE;
+	return true;
 }
 
 static int got_Ping(struct drbd_conf *mdev, struct p_header80 *h)
@@ -4154,7 +4240,7 @@ static int got_PingAck(struct drbd_conf *mdev, struct p_header80 *h)
 	if (!test_and_set_bit(GOT_PING_ACK, &mdev->flags))
 		wake_up(&mdev->misc_wait);
 
-	return TRUE;
+	return true;
 }
 
 static int got_IsInSync(struct drbd_conf *mdev, struct p_header80 *h)
@@ -4177,7 +4263,7 @@ static int got_IsInSync(struct drbd_conf *mdev, struct p_header80 *h)
 	dec_rs_pending(mdev);
 	atomic_add(blksize >> 9, &mdev->rs_sect_in);
 
-	return TRUE;
+	return true;
 }
 
 /* when we receive the ACK for a write request,
@@ -4201,8 +4287,6 @@ static struct drbd_request *_ack_id_to_req(struct drbd_conf *mdev,
 			return req;
 		}
 	}
-	dev_err(DEV, "_ack_id_to_req: failed to find req %p, sector %llus in list\n",
-		(void *)(unsigned long)id, (unsigned long long)sector);
 	return NULL;
 }
 
@@ -4220,15 +4304,17 @@ static int validate_req_change_req_state(struct drbd_conf *mdev,
 	req = validator(mdev, id, sector);
 	if (unlikely(!req)) {
 		spin_unlock_irq(&mdev->req_lock);
-		dev_err(DEV, "%s: got a corrupt block_id/sector pair\n", func);
-		return FALSE;
+
+		dev_err(DEV, "%s: failed to find req %p, sector %llus\n", func,
+			(void *)(unsigned long)id, (unsigned long long)sector);
+		return false;
 	}
 	__req_mod(req, what, &m);
 	spin_unlock_irq(&mdev->req_lock);
 
 	if (m.bio)
 		complete_master_bio(mdev, &m);
-	return TRUE;
+	return true;
 }
 
 static int got_BlockAck(struct drbd_conf *mdev, struct p_header80 *h)
@@ -4243,7 +4329,7 @@ static int got_BlockAck(struct drbd_conf *mdev, struct p_header80 *h)
 	if (is_syncer_block_id(p->block_id)) {
 		drbd_set_in_sync(mdev, sector, blksize);
 		dec_rs_pending(mdev);
-		return TRUE;
+		return true;
 	}
 	switch (be16_to_cpu(h->command)) {
 	case P_RS_WRITE_ACK:
@@ -4264,7 +4350,7 @@ static int got_BlockAck(struct drbd_conf *mdev, struct p_header80 *h)
 		break;
 	default:
 		D_ASSERT(0);
-		return FALSE;
+		return false;
 	}
 
 	return validate_req_change_req_state(mdev, p->block_id, sector,
@@ -4275,20 +4361,44 @@ static int got_NegAck(struct drbd_conf *mdev, struct p_header80 *h)
 {
 	struct p_block_ack *p = (struct p_block_ack *)h;
 	sector_t sector = be64_to_cpu(p->sector);
-
-	if (__ratelimit(&drbd_ratelimit_state))
-		dev_warn(DEV, "Got NegAck packet. Peer is in troubles?\n");
+	int size = be32_to_cpu(p->blksize);
+	struct drbd_request *req;
+	struct bio_and_error m;
 
 	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
 
 	if (is_syncer_block_id(p->block_id)) {
-		int size = be32_to_cpu(p->blksize);
 		dec_rs_pending(mdev);
 		drbd_rs_failed_io(mdev, sector, size);
-		return TRUE;
+		return true;
 	}
-	return validate_req_change_req_state(mdev, p->block_id, sector,
-		_ack_id_to_req, __func__ , neg_acked);
+
+	spin_lock_irq(&mdev->req_lock);
+	req = _ack_id_to_req(mdev, p->block_id, sector);
+	if (!req) {
+		spin_unlock_irq(&mdev->req_lock);
+		if (mdev->net_conf->wire_protocol == DRBD_PROT_A ||
+		    mdev->net_conf->wire_protocol == DRBD_PROT_B) {
+			/* Protocol A has no P_WRITE_ACKs, but has P_NEG_ACKs.
+			   The master bio might already be completed, therefore the
+			   request is no longer in the collision hash.
+			   => Do not try to validate block_id as request. */
+			/* In Protocol B we might already have got a P_RECV_ACK
+			   but then get a P_NEG_ACK after wards. */
+			drbd_set_out_of_sync(mdev, sector, size);
+			return true;
+		} else {
+			dev_err(DEV, "%s: failed to find req %p, sector %llus\n", __func__,
+				(void *)(unsigned long)p->block_id, (unsigned long long)sector);
+			return false;
+		}
+	}
+	__req_mod(req, neg_acked, &m);
+	spin_unlock_irq(&mdev->req_lock);
+
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+	return true;
 }
 
 static int got_NegDReply(struct drbd_conf *mdev, struct p_header80 *h)
@@ -4319,11 +4429,20 @@ static int got_NegRSDReply(struct drbd_conf *mdev, struct p_header80 *h)
 
 	if (get_ldev_if_state(mdev, D_FAILED)) {
 		drbd_rs_complete_io(mdev, sector);
-		drbd_rs_failed_io(mdev, sector, size);
+		switch (be16_to_cpu(h->command)) {
+		case P_NEG_RS_DREPLY:
+			drbd_rs_failed_io(mdev, sector, size);
+		case P_RS_CANCEL:
+			break;
+		default:
+			D_ASSERT(0);
+			put_ldev(mdev);
+			return false;
+		}
 		put_ldev(mdev);
 	}
 
-	return TRUE;
+	return true;
 }
 
 static int got_BarrierAck(struct drbd_conf *mdev, struct p_header80 *h)
@@ -4332,7 +4451,14 @@ static int got_BarrierAck(struct drbd_conf *mdev, struct p_header80 *h)
 
 	tl_release(mdev, p->barrier, be32_to_cpu(p->set_size));
 
-	return TRUE;
+	if (mdev->state.conn == C_AHEAD &&
+	    atomic_read(&mdev->ap_in_flight) == 0 &&
+	    !test_and_set_bit(AHEAD_TO_SYNC_SOURCE, &mdev->current_epoch->flags)) {
+		mdev->start_resync_timer.expires = jiffies + HZ;
+		add_timer(&mdev->start_resync_timer);
+	}
+
+	return true;
 }
 
 static int got_OVResult(struct drbd_conf *mdev, struct p_header80 *h)
@@ -4353,12 +4479,18 @@ static int got_OVResult(struct drbd_conf *mdev, struct p_header80 *h)
 		ov_oos_print(mdev);
 
 	if (!get_ldev(mdev))
-		return TRUE;
+		return true;
 
 	drbd_rs_complete_io(mdev, sector);
 	dec_rs_pending(mdev);
 
-	if (--mdev->ov_left == 0) {
+	--mdev->ov_left;
+
+	/* let's advance progress step marks only for every other megabyte */
+	if ((mdev->ov_left & 0x200) == 0x200)
+		drbd_advance_rs_marks(mdev, mdev->ov_left);
+
+	if (mdev->ov_left == 0) {
 		w = kmalloc(sizeof(*w), GFP_NOIO);
 		if (w) {
 			w->cb = w_ov_finished;
@@ -4370,12 +4502,12 @@ static int got_OVResult(struct drbd_conf *mdev, struct p_header80 *h)
 		}
 	}
 	put_ldev(mdev);
-	return TRUE;
+	return true;
 }
 
 static int got_skip(struct drbd_conf *mdev, struct p_header80 *h)
 {
-	return TRUE;
+	return true;
 }
 
 struct asender_cmd {
@@ -4403,6 +4535,7 @@ static struct asender_cmd *get_asender_cmd(int cmd)
 	[P_STATE_CHG_REPLY] = { sizeof(struct p_req_state_reply), got_RqSReply },
 	[P_RS_IS_IN_SYNC]   = { sizeof(struct p_block_ack), got_IsInSync },
 	[P_DELAY_PROBE]     = { sizeof(struct p_delay_probe93), got_skip },
+	[P_RS_CANCEL]       = { sizeof(struct p_block_ack), got_NegRSDReply},
 	[P_MAX_CMD]	    = { 0, NULL },
 	};
 	if (cmd > P_MAX_CMD || asender_tbl[cmd].process == NULL)
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 11a75d32a2e..5c0c8be1bb0 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -140,9 +140,14 @@ static void _about_to_complete_local_write(struct drbd_conf *mdev,
 	struct hlist_node *n;
 	struct hlist_head *slot;
 
-	/* before we can signal completion to the upper layers,
-	 * we may need to close the current epoch */
+	/* Before we can signal completion to the upper layers,
+	 * we may need to close the current epoch.
+	 * We can skip this, if this request has not even been sent, because we
+	 * did not have a fully established connection yet/anymore, during
+	 * bitmap exchange, or while we are C_AHEAD due to congestion policy.
+	 */
 	if (mdev->state.conn >= C_CONNECTED &&
+	    (s & RQ_NET_SENT) != 0 &&
 	    req->epoch == mdev->newest_tle->br_number)
 		queue_barrier(mdev);
 
@@ -440,7 +445,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		req->rq_state |= RQ_LOCAL_COMPLETED;
 		req->rq_state &= ~RQ_LOCAL_PENDING;
 
-		__drbd_chk_io_error(mdev, FALSE);
+		__drbd_chk_io_error(mdev, false);
 		_req_may_be_done_not_susp(req, m);
 		put_ldev(mdev);
 		break;
@@ -461,7 +466,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 		D_ASSERT(!(req->rq_state & RQ_NET_MASK));
 
-		__drbd_chk_io_error(mdev, FALSE);
+		__drbd_chk_io_error(mdev, false);
 		put_ldev(mdev);
 
 		/* no point in retrying if there is no good remote data,
@@ -545,6 +550,14 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 		break;
 
+	case queue_for_send_oos:
+		req->rq_state |= RQ_NET_QUEUED;
+		req->w.cb =  w_send_oos;
+		drbd_queue_work(&mdev->data.work, &req->w);
+		break;
+
+	case oos_handed_to_network:
+		/* actually the same */
 	case send_canceled:
 		/* treat it the same */
 	case send_failed:
@@ -558,6 +571,9 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 	case handed_over_to_network:
 		/* assert something? */
+		if (bio_data_dir(req->master_bio) == WRITE)
+			atomic_add(req->size>>9, &mdev->ap_in_flight);
+
 		if (bio_data_dir(req->master_bio) == WRITE &&
 		    mdev->net_conf->wire_protocol == DRBD_PROT_A) {
 			/* this is what is dangerous about protocol A:
@@ -591,6 +607,9 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 			dec_ap_pending(mdev);
 		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 		req->rq_state |= RQ_NET_DONE;
+		if (req->rq_state & RQ_NET_SENT && req->rq_state & RQ_WRITE)
+			atomic_sub(req->size>>9, &mdev->ap_in_flight);
+
 		/* if it is still queued, we may not complete it here.
 		 * it will be canceled soon. */
 		if (!(req->rq_state & RQ_NET_QUEUED))
@@ -628,14 +647,17 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		req->rq_state |= RQ_NET_OK;
 		D_ASSERT(req->rq_state & RQ_NET_PENDING);
 		dec_ap_pending(mdev);
+		atomic_sub(req->size>>9, &mdev->ap_in_flight);
 		req->rq_state &= ~RQ_NET_PENDING;
 		_req_may_be_done_not_susp(req, m);
 		break;
 
 	case neg_acked:
 		/* assert something? */
-		if (req->rq_state & RQ_NET_PENDING)
+		if (req->rq_state & RQ_NET_PENDING) {
 			dec_ap_pending(mdev);
+			atomic_sub(req->size>>9, &mdev->ap_in_flight);
+		}
 		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 
 		req->rq_state |= RQ_NET_DONE;
@@ -690,8 +712,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 			dev_err(DEV, "FIXME (barrier_acked but pending)\n");
 			list_move(&req->tl_requests, &mdev->out_of_sequence_requests);
 		}
-		D_ASSERT(req->rq_state & RQ_NET_SENT);
-		req->rq_state |= RQ_NET_DONE;
+		if ((req->rq_state & RQ_NET_MASK) != 0) {
+			req->rq_state |= RQ_NET_DONE;
+			if (mdev->net_conf->wire_protocol == DRBD_PROT_A)
+				atomic_sub(req->size>>9, &mdev->ap_in_flight);
+		}
 		_req_may_be_done(req, m); /* Allowed while state.susp */
 		break;
 
@@ -738,14 +763,14 @@ static int drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int s
 	return 0 == drbd_bm_count_bits(mdev, sbnr, ebnr);
 }
 
-static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
+static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, unsigned long start_time)
 {
 	const int rw = bio_rw(bio);
 	const int size = bio->bi_size;
 	const sector_t sector = bio->bi_sector;
 	struct drbd_tl_epoch *b = NULL;
 	struct drbd_request *req;
-	int local, remote;
+	int local, remote, send_oos = 0;
 	int err = -EIO;
 	int ret = 0;
 
@@ -759,6 +784,7 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
 		bio_endio(bio, -ENOMEM);
 		return 0;
 	}
+	req->start_time = start_time;
 
 	local = get_ldev(mdev);
 	if (!local) {
@@ -808,9 +834,9 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
 		drbd_al_begin_io(mdev, sector);
 	}
 
-	remote = remote && (mdev->state.pdsk == D_UP_TO_DATE ||
-			    (mdev->state.pdsk == D_INCONSISTENT &&
-			     mdev->state.conn >= C_CONNECTED));
+	remote = remote && drbd_should_do_remote(mdev->state);
+	send_oos = rw == WRITE && drbd_should_send_oos(mdev->state);
+	D_ASSERT(!(remote && send_oos));
 
 	if (!(local || remote) && !is_susp(mdev->state)) {
 		if (__ratelimit(&drbd_ratelimit_state))
@@ -824,7 +850,7 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
 	 * but there is a race between testing the bit and pointer outside the
 	 * spinlock, and grabbing the spinlock.
 	 * if we lost that race, we retry.  */
-	if (rw == WRITE && remote &&
+	if (rw == WRITE && (remote || send_oos) &&
 	    mdev->unused_spare_tle == NULL &&
 	    test_bit(CREATE_BARRIER, &mdev->flags)) {
 allocate_barrier:
@@ -842,18 +868,19 @@ allocate_barrier:
 	if (is_susp(mdev->state)) {
 		/* If we got suspended, use the retry mechanism of
 		   generic_make_request() to restart processing of this
-		   bio. In the next call to drbd_make_request_26
+		   bio. In the next call to drbd_make_request
 		   we sleep in inc_ap_bio() */
 		ret = 1;
 		spin_unlock_irq(&mdev->req_lock);
 		goto fail_free_complete;
 	}
 
-	if (remote) {
-		remote = (mdev->state.pdsk == D_UP_TO_DATE ||
-			    (mdev->state.pdsk == D_INCONSISTENT &&
-			     mdev->state.conn >= C_CONNECTED));
-		if (!remote)
+	if (remote || send_oos) {
+		remote = drbd_should_do_remote(mdev->state);
+		send_oos = rw == WRITE && drbd_should_send_oos(mdev->state);
+		D_ASSERT(!(remote && send_oos));
+
+		if (!(remote || send_oos))
 			dev_warn(DEV, "lost connection while grabbing the req_lock!\n");
 		if (!(local || remote)) {
 			dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
@@ -866,7 +893,7 @@ allocate_barrier:
 		mdev->unused_spare_tle = b;
 		b = NULL;
 	}
-	if (rw == WRITE && remote &&
+	if (rw == WRITE && (remote || send_oos) &&
 	    mdev->unused_spare_tle == NULL &&
 	    test_bit(CREATE_BARRIER, &mdev->flags)) {
 		/* someone closed the current epoch
@@ -889,7 +916,7 @@ allocate_barrier:
 	 * barrier packet.  To get the write ordering right, we only have to
 	 * make sure that, if this is a write request and it triggered a
 	 * barrier packet, this request is queued within the same spinlock. */
-	if (remote && mdev->unused_spare_tle &&
+	if ((remote || send_oos) && mdev->unused_spare_tle &&
 	    test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
 		_tl_add_barrier(mdev, mdev->unused_spare_tle);
 		mdev->unused_spare_tle = NULL;
@@ -937,6 +964,34 @@ allocate_barrier:
 				? queue_for_net_write
 				: queue_for_net_read);
 	}
+	if (send_oos && drbd_set_out_of_sync(mdev, sector, size))
+		_req_mod(req, queue_for_send_oos);
+
+	if (remote &&
+	    mdev->net_conf->on_congestion != OC_BLOCK && mdev->agreed_pro_version >= 96) {
+		int congested = 0;
+
+		if (mdev->net_conf->cong_fill &&
+		    atomic_read(&mdev->ap_in_flight) >= mdev->net_conf->cong_fill) {
+			dev_info(DEV, "Congestion-fill threshold reached\n");
+			congested = 1;
+		}
+
+		if (mdev->act_log->used >= mdev->net_conf->cong_extents) {
+			dev_info(DEV, "Congestion-extents threshold reached\n");
+			congested = 1;
+		}
+
+		if (congested) {
+			queue_barrier(mdev); /* last barrier, after mirrored writes */
+
+			if (mdev->net_conf->on_congestion == OC_PULL_AHEAD)
+				_drbd_set_state(_NS(mdev, conn, C_AHEAD), 0, NULL);
+			else  /*mdev->net_conf->on_congestion == OC_DISCONNECT */
+				_drbd_set_state(_NS(mdev, conn, C_DISCONNECTING), 0, NULL);
+		}
+	}
+
 	spin_unlock_irq(&mdev->req_lock);
 	kfree(b); /* if someone else has beaten us to it... */
 
@@ -949,9 +1004,9 @@ allocate_barrier:
 		 * stable storage, and this is a WRITE, we may not even submit
 		 * this bio. */
 		if (get_ldev(mdev)) {
-			if (FAULT_ACTIVE(mdev, rw == WRITE ? DRBD_FAULT_DT_WR
-					     : rw == READ  ? DRBD_FAULT_DT_RD
-					     :               DRBD_FAULT_DT_RA))
+			if (drbd_insert_fault(mdev,   rw == WRITE ? DRBD_FAULT_DT_WR
+						    : rw == READ  ? DRBD_FAULT_DT_RD
+						    :               DRBD_FAULT_DT_RA))
 				bio_endio(req->private_bio, -EIO);
 			else
 				generic_make_request(req->private_bio);
@@ -960,10 +1015,6 @@ allocate_barrier:
 			bio_endio(req->private_bio, -EIO);
 	}
 
-	/* we need to plug ALWAYS since we possibly need to kick lo_dev.
-	 * we plug after submit, so we won't miss an unplug event */
-	drbd_plug_device(mdev);
-
 	return 0;
 
 fail_conflicting:
@@ -1022,16 +1073,19 @@ static int drbd_fail_request_early(struct drbd_conf *mdev, int is_write)
 	return 0;
 }
 
-int drbd_make_request_26(struct request_queue *q, struct bio *bio)
+int drbd_make_request(struct request_queue *q, struct bio *bio)
 {
 	unsigned int s_enr, e_enr;
 	struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+	unsigned long start_time;
 
 	if (drbd_fail_request_early(mdev, bio_data_dir(bio) & WRITE)) {
 		bio_endio(bio, -EPERM);
 		return 0;
 	}
 
+	start_time = jiffies;
+
 	/*
 	 * what we "blindly" assume:
 	 */
@@ -1046,12 +1100,12 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
 
 	if (likely(s_enr == e_enr)) {
 		inc_ap_bio(mdev, 1);
-		return drbd_make_request_common(mdev, bio);
+		return drbd_make_request_common(mdev, bio, start_time);
 	}
 
 	/* can this bio be split generically?
 	 * Maybe add our own split-arbitrary-bios function. */
-	if (bio->bi_vcnt != 1 || bio->bi_idx != 0 || bio->bi_size > DRBD_MAX_SEGMENT_SIZE) {
+	if (bio->bi_vcnt != 1 || bio->bi_idx != 0 || bio->bi_size > DRBD_MAX_BIO_SIZE) {
 		/* rather error out here than BUG in bio_split */
 		dev_err(DEV, "bio would need to, but cannot, be split: "
 		    "(vcnt=%u,idx=%u,size=%u,sector=%llu)\n",
@@ -1073,11 +1127,7 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
 		const int sps = 1 << HT_SHIFT; /* sectors per slot */
 		const int mask = sps - 1;
 		const sector_t first_sectors = sps - (sect & mask);
-		bp = bio_split(bio,
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
-				bio_split_pool,
-#endif
-				first_sectors);
+		bp = bio_split(bio, first_sectors);
 
 		/* we need to get a "reference count" (ap_bio_cnt)
 		 * to avoid races with the disconnect/reconnect/suspend code.
@@ -1088,10 +1138,10 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
 
 		D_ASSERT(e_enr == s_enr + 1);
 
-		while (drbd_make_request_common(mdev, &bp->bio1))
+		while (drbd_make_request_common(mdev, &bp->bio1, start_time))
 			inc_ap_bio(mdev, 1);
 
-		while (drbd_make_request_common(mdev, &bp->bio2))
+		while (drbd_make_request_common(mdev, &bp->bio2, start_time))
 			inc_ap_bio(mdev, 1);
 
 		dec_ap_bio(mdev);
@@ -1102,7 +1152,7 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
 }
 
 /* This is called by bio_add_page().  With this function we reduce
- * the number of BIOs that span over multiple DRBD_MAX_SEGMENT_SIZEs
+ * the number of BIOs that span over multiple DRBD_MAX_BIO_SIZEs
  * units (was AL_EXTENTs).
  *
  * we do the calculation within the lower 32bit of the byte offsets,
@@ -1112,7 +1162,7 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
  * As long as the BIO is empty we have to allow at least one bvec,
  * regardless of size and offset.  so the resulting bio may still
  * cross extent boundaries.  those are dealt with (bio_split) in
- * drbd_make_request_26.
+ * drbd_make_request.
  */
 int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
 {
@@ -1122,8 +1172,8 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
 	unsigned int bio_size = bvm->bi_size;
 	int limit, backing_limit;
 
-	limit = DRBD_MAX_SEGMENT_SIZE
-	      - ((bio_offset & (DRBD_MAX_SEGMENT_SIZE-1)) + bio_size);
+	limit = DRBD_MAX_BIO_SIZE
+	      - ((bio_offset & (DRBD_MAX_BIO_SIZE-1)) + bio_size);
 	if (limit < 0)
 		limit = 0;
 	if (bio_size == 0) {
@@ -1140,3 +1190,42 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
 	}
 	return limit;
 }
+
+void request_timer_fn(unsigned long data)
+{
+	struct drbd_conf *mdev = (struct drbd_conf *) data;
+	struct drbd_request *req; /* oldest request */
+	struct list_head *le;
+	unsigned long et = 0; /* effective timeout = ko_count * timeout */
+
+	if (get_net_conf(mdev)) {
+		et = mdev->net_conf->timeout*HZ/10 * mdev->net_conf->ko_count;
+		put_net_conf(mdev);
+	}
+	if (!et || mdev->state.conn < C_WF_REPORT_PARAMS)
+		return; /* Recurring timer stopped */
+
+	spin_lock_irq(&mdev->req_lock);
+	le = &mdev->oldest_tle->requests;
+	if (list_empty(le)) {
+		spin_unlock_irq(&mdev->req_lock);
+		mod_timer(&mdev->request_timer, jiffies + et);
+		return;
+	}
+
+	le = le->prev;
+	req = list_entry(le, struct drbd_request, tl_requests);
+	if (time_is_before_eq_jiffies(req->start_time + et)) {
+		if (req->rq_state & RQ_NET_PENDING) {
+			dev_warn(DEV, "Remote failed to finish a request within ko-count * timeout\n");
+			_drbd_set_state(_NS(mdev, conn, C_TIMEOUT), CS_VERBOSE, NULL);
+		} else {
+			dev_warn(DEV, "Local backing block device frozen?\n");
+			mod_timer(&mdev->request_timer, jiffies + et);
+		}
+	} else {
+		mod_timer(&mdev->request_timer, req->start_time + et);
+	}
+
+	spin_unlock_irq(&mdev->req_lock);
+}
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index ab2bd09d54b..32e2c3e6a81 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -82,14 +82,16 @@ enum drbd_req_event {
 	to_be_submitted,
 
 	/* XXX yes, now I am inconsistent...
-	 * these two are not "events" but "actions"
+	 * these are not "events" but "actions"
 	 * oh, well... */
 	queue_for_net_write,
 	queue_for_net_read,
+	queue_for_send_oos,
 
 	send_canceled,
 	send_failed,
 	handed_over_to_network,
+	oos_handed_to_network,
 	connection_lost_while_pending,
 	read_retry_remote_canceled,
 	recv_acked_by_peer,
@@ -289,7 +291,6 @@ static inline struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
 		req->epoch       = 0;
 		req->sector      = bio_src->bi_sector;
 		req->size        = bio_src->bi_size;
-		req->start_time  = jiffies;
 		INIT_HLIST_NODE(&req->colision);
 		INIT_LIST_HEAD(&req->tl_requests);
 		INIT_LIST_HEAD(&req->w.list);
@@ -321,6 +322,7 @@ extern int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		struct bio_and_error *m);
 extern void complete_master_bio(struct drbd_conf *mdev,
 		struct bio_and_error *m);
+extern void request_timer_fn(unsigned long data);
 
 /* use this if you don't want to deal with calling complete_master_bio()
  * outside the spinlock, e.g. when walking some list on cleanup. */
@@ -338,23 +340,43 @@ static inline int _req_mod(struct drbd_request *req, enum drbd_req_event what)
 	return rv;
 }
 
-/* completion of master bio is outside of spinlock.
- * If you need it irqsave, do it your self!
- * Which means: don't use from bio endio callback. */
+/* completion of master bio is outside of our spinlock.
+ * We still may or may not be inside some irqs disabled section
+ * of the lower level driver completion callback, so we need to
+ * spin_lock_irqsave here. */
 static inline int req_mod(struct drbd_request *req,
 		enum drbd_req_event what)
 {
+	unsigned long flags;
 	struct drbd_conf *mdev = req->mdev;
 	struct bio_and_error m;
 	int rv;
 
-	spin_lock_irq(&mdev->req_lock);
+	spin_lock_irqsave(&mdev->req_lock, flags);
 	rv = __req_mod(req, what, &m);
-	spin_unlock_irq(&mdev->req_lock);
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
 
 	if (m.bio)
 		complete_master_bio(mdev, &m);
 
 	return rv;
 }
+
+static inline bool drbd_should_do_remote(union drbd_state s)
+{
+	return s.pdsk == D_UP_TO_DATE ||
+		(s.pdsk >= D_INCONSISTENT &&
+		 s.conn >= C_WF_BITMAP_T &&
+		 s.conn < C_AHEAD);
+	/* Before proto 96 that was >= CONNECTED instead of >= C_WF_BITMAP_T.
+	   That is equivalent since before 96 IO was frozen in the C_WF_BITMAP*
+	   states. */
+}
+static inline bool drbd_should_send_oos(union drbd_state s)
+{
+	return s.conn == C_AHEAD || s.conn == C_WF_BITMAP_S;
+	/* pdsk = D_INCONSISTENT as a consequence. Protocol 96 check not necessary
+	   since we enter state C_AHEAD only if proto >= 96 */
+}
+
 #endif
diff --git a/drivers/block/drbd/drbd_strings.c b/drivers/block/drbd/drbd_strings.c
index 85179e1fb50..c44a2a60277 100644
--- a/drivers/block/drbd/drbd_strings.c
+++ b/drivers/block/drbd/drbd_strings.c
@@ -48,6 +48,8 @@ static const char *drbd_conn_s_names[] = {
 	[C_PAUSED_SYNC_T]    = "PausedSyncT",
 	[C_VERIFY_S]         = "VerifyS",
 	[C_VERIFY_T]         = "VerifyT",
+	[C_AHEAD]            = "Ahead",
+	[C_BEHIND]           = "Behind",
 };
 
 static const char *drbd_role_s_names[] = {
@@ -92,7 +94,7 @@ static const char *drbd_state_sw_errors[] = {
 const char *drbd_conn_str(enum drbd_conns s)
 {
 	/* enums are unsigned... */
-	return s > C_PAUSED_SYNC_T ? "TOO_LARGE" : drbd_conn_s_names[s];
+	return s > C_BEHIND ? "TOO_LARGE" : drbd_conn_s_names[s];
 }
 
 const char *drbd_role_str(enum drbd_role s)
@@ -105,7 +107,7 @@ const char *drbd_disk_str(enum drbd_disk_state s)
 	return s > D_UP_TO_DATE    ? "TOO_LARGE" : drbd_disk_s_names[s];
 }
 
-const char *drbd_set_st_err_str(enum drbd_state_ret_codes err)
+const char *drbd_set_st_err_str(enum drbd_state_rv err)
 {
 	return err <= SS_AFTER_LAST_ERROR ? "TOO_SMALL" :
 	       err > SS_TWO_PRIMARIES ? "TOO_LARGE"
diff --git a/drivers/block/drbd/drbd_vli.h b/drivers/block/drbd/drbd_vli.h
index fc824006e72..8cb1532a381 100644
--- a/drivers/block/drbd/drbd_vli.h
+++ b/drivers/block/drbd/drbd_vli.h
@@ -32,7 +32,7 @@
  * the bitmap transfer time can take much too long,
  * if transmitted in plain text.
  *
- * We try to reduce the transfered bitmap information
+ * We try to reduce the transferred bitmap information
  * by encoding runlengths of bit polarity.
  *
  * We never actually need to encode a "zero" (runlengths are positive).
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 34f224b018b..f7e6c92f8d0 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -39,18 +39,17 @@
 #include "drbd_req.h"
 
 static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int cancel);
+static int w_make_resync_request(struct drbd_conf *mdev,
+				 struct drbd_work *w, int cancel);
 
 
 
-/* defined here:
-   drbd_md_io_complete
-   drbd_endio_sec
-   drbd_endio_pri
-
- * more endio handlers:
-   atodb_endio in drbd_actlog.c
-   drbd_bm_async_io_complete in drbd_bitmap.c
-
+/* endio handlers:
+ *   drbd_md_io_complete (defined here)
+ *   drbd_endio_pri (defined here)
+ *   drbd_endio_sec (defined here)
+ *   bm_async_io_complete (defined in drbd_bitmap.c)
+ *
  * For all these callbacks, note the following:
  * The callbacks will be called in irq context by the IDE drivers,
  * and in Softirqs/Tasklets/BH context by the SCSI drivers.
@@ -94,7 +93,7 @@ void drbd_endio_read_sec_final(struct drbd_epoch_entry *e) __releases(local)
 	if (list_empty(&mdev->read_ee))
 		wake_up(&mdev->ee_wait);
 	if (test_bit(__EE_WAS_ERROR, &e->flags))
-		__drbd_chk_io_error(mdev, FALSE);
+		__drbd_chk_io_error(mdev, false);
 	spin_unlock_irqrestore(&mdev->req_lock, flags);
 
 	drbd_queue_work(&mdev->data.work, &e->w);
@@ -137,7 +136,7 @@ static void drbd_endio_write_sec_final(struct drbd_epoch_entry *e) __releases(lo
 		: list_empty(&mdev->active_ee);
 
 	if (test_bit(__EE_WAS_ERROR, &e->flags))
-		__drbd_chk_io_error(mdev, FALSE);
+		__drbd_chk_io_error(mdev, false);
 	spin_unlock_irqrestore(&mdev->req_lock, flags);
 
 	if (is_syncer_req)
@@ -163,14 +162,15 @@ void drbd_endio_sec(struct bio *bio, int error)
 	int uptodate = bio_flagged(bio, BIO_UPTODATE);
 	int is_write = bio_data_dir(bio) == WRITE;
 
-	if (error)
+	if (error && __ratelimit(&drbd_ratelimit_state))
 		dev_warn(DEV, "%s: error=%d s=%llus\n",
 				is_write ? "write" : "read", error,
 				(unsigned long long)e->sector);
 	if (!error && !uptodate) {
-		dev_warn(DEV, "%s: setting error to -EIO s=%llus\n",
-				is_write ? "write" : "read",
-				(unsigned long long)e->sector);
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_warn(DEV, "%s: setting error to -EIO s=%llus\n",
+					is_write ? "write" : "read",
+					(unsigned long long)e->sector);
 		/* strange behavior of some lower level drivers...
 		 * fail the request by clearing the uptodate flag,
 		 * but do not return any error?! */
@@ -250,13 +250,6 @@ int w_read_retry_remote(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 	return w_send_read_req(mdev, w, 0);
 }
 
-int w_resync_inactive(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
-{
-	ERR_IF(cancel) return 1;
-	dev_err(DEV, "resync inactive, but callback triggered??\n");
-	return 1; /* Simply ignore this! */
-}
-
 void drbd_csum_ee(struct drbd_conf *mdev, struct crypto_hash *tfm, struct drbd_epoch_entry *e, void *digest)
 {
 	struct hash_desc desc;
@@ -355,7 +348,7 @@ static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
 	if (!get_ldev(mdev))
 		return -EIO;
 
-	if (drbd_rs_should_slow_down(mdev))
+	if (drbd_rs_should_slow_down(mdev, sector))
 		goto defer;
 
 	/* GFP_TRY, because if there is no memory available right now, this may
@@ -373,9 +366,10 @@ static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
 	if (drbd_submit_ee(mdev, e, READ, DRBD_FAULT_RS_RD) == 0)
 		return 0;
 
-	/* drbd_submit_ee currently fails for one reason only:
-	 * not being able to allocate enough bios.
-	 * Is dropping the connection going to help? */
+	/* If it failed because of ENOMEM, retry should help.  If it failed
+	 * because bio_add_page failed (probably broken lower level driver),
+	 * retry may or may not help.
+	 * If it does not, you may need to force disconnect. */
 	spin_lock_irq(&mdev->req_lock);
 	list_del(&e->w.list);
 	spin_unlock_irq(&mdev->req_lock);
@@ -386,26 +380,25 @@ defer:
 	return -EAGAIN;
 }
 
-void resync_timer_fn(unsigned long data)
+int w_resync_timer(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 {
-	struct drbd_conf *mdev = (struct drbd_conf *) data;
-	int queue;
-
-	queue = 1;
 	switch (mdev->state.conn) {
 	case C_VERIFY_S:
-		mdev->resync_work.cb = w_make_ov_request;
+		w_make_ov_request(mdev, w, cancel);
 		break;
 	case C_SYNC_TARGET:
-		mdev->resync_work.cb = w_make_resync_request;
+		w_make_resync_request(mdev, w, cancel);
 		break;
-	default:
-		queue = 0;
-		mdev->resync_work.cb = w_resync_inactive;
 	}
 
-	/* harmless race: list_empty outside data.work.q_lock */
-	if (list_empty(&mdev->resync_work.list) && queue)
+	return 1;
+}
+
+void resync_timer_fn(unsigned long data)
+{
+	struct drbd_conf *mdev = (struct drbd_conf *) data;
+
+	if (list_empty(&mdev->resync_work.list))
 		drbd_queue_work(&mdev->data.work, &mdev->resync_work);
 }
 
@@ -438,7 +431,7 @@ static void fifo_add_val(struct fifo_buffer *fb, int value)
 		fb->values[i] += value;
 }
 
-int drbd_rs_controller(struct drbd_conf *mdev)
+static int drbd_rs_controller(struct drbd_conf *mdev)
 {
 	unsigned int sect_in;  /* Number of sectors that came in since the last turn */
 	unsigned int want;     /* The number of sectors we want in the proxy */
@@ -492,29 +485,36 @@ int drbd_rs_controller(struct drbd_conf *mdev)
 	return req_sect;
 }
 
-int w_make_resync_request(struct drbd_conf *mdev,
-		struct drbd_work *w, int cancel)
+static int drbd_rs_number_requests(struct drbd_conf *mdev)
+{
+	int number;
+	if (mdev->rs_plan_s.size) { /* mdev->sync_conf.c_plan_ahead */
+		number = drbd_rs_controller(mdev) >> (BM_BLOCK_SHIFT - 9);
+		mdev->c_sync_rate = number * HZ * (BM_BLOCK_SIZE / 1024) / SLEEP_TIME;
+	} else {
+		mdev->c_sync_rate = mdev->sync_conf.rate;
+		number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
+	}
+
+	/* ignore the amount of pending requests, the resync controller should
+	 * throttle down to incoming reply rate soon enough anyways. */
+	return number;
+}
+
+static int w_make_resync_request(struct drbd_conf *mdev,
+				 struct drbd_work *w, int cancel)
 {
 	unsigned long bit;
 	sector_t sector;
 	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
-	int max_segment_size;
-	int number, rollback_i, size, pe, mx;
+	int max_bio_size;
+	int number, rollback_i, size;
 	int align, queued, sndbuf;
 	int i = 0;
 
 	if (unlikely(cancel))
 		return 1;
 
-	if (unlikely(mdev->state.conn < C_CONNECTED)) {
-		dev_err(DEV, "Confused in w_make_resync_request()! cstate < Connected");
-		return 0;
-	}
-
-	if (mdev->state.conn != C_SYNC_TARGET)
-		dev_err(DEV, "%s in w_make_resync_request\n",
-			drbd_conn_str(mdev->state.conn));
-
 	if (mdev->rs_total == 0) {
 		/* empty resync? */
 		drbd_resync_finished(mdev);
@@ -527,49 +527,19 @@ int w_make_resync_request(struct drbd_conf *mdev,
 		   to continue resync with a broken disk makes no sense at
 		   all */
 		dev_err(DEV, "Disk broke down during resync!\n");
-		mdev->resync_work.cb = w_resync_inactive;
 		return 1;
 	}
 
 	/* starting with drbd 8.3.8, we can handle multi-bio EEs,
 	 * if it should be necessary */
-	max_segment_size =
-		mdev->agreed_pro_version < 94 ? queue_max_segment_size(mdev->rq_queue) :
-		mdev->agreed_pro_version < 95 ?	DRBD_MAX_SIZE_H80_PACKET : DRBD_MAX_SEGMENT_SIZE;
+	max_bio_size =
+		mdev->agreed_pro_version < 94 ? queue_max_hw_sectors(mdev->rq_queue) << 9 :
+		mdev->agreed_pro_version < 95 ?	DRBD_MAX_SIZE_H80_PACKET : DRBD_MAX_BIO_SIZE;
 
-	if (mdev->rs_plan_s.size) { /* mdev->sync_conf.c_plan_ahead */
-		number = drbd_rs_controller(mdev) >> (BM_BLOCK_SHIFT - 9);
-		mdev->c_sync_rate = number * HZ * (BM_BLOCK_SIZE / 1024) / SLEEP_TIME;
-	} else {
-		mdev->c_sync_rate = mdev->sync_conf.rate;
-		number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
-	}
-
-	/* Throttle resync on lower level disk activity, which may also be
-	 * caused by application IO on Primary/SyncTarget.
-	 * Keep this after the call to drbd_rs_controller, as that assumes
-	 * to be called as precisely as possible every SLEEP_TIME,
-	 * and would be confused otherwise. */
-	if (drbd_rs_should_slow_down(mdev))
+	number = drbd_rs_number_requests(mdev);
+	if (number == 0)
 		goto requeue;
 
-	mutex_lock(&mdev->data.mutex);
-	if (mdev->data.socket)
-		mx = mdev->data.socket->sk->sk_rcvbuf / sizeof(struct p_block_req);
-	else
-		mx = 1;
-	mutex_unlock(&mdev->data.mutex);
-
-	/* For resync rates >160MB/sec, allow more pending RS requests */
-	if (number > mx)
-		mx = number;
-
-	/* Limit the number of pending RS requests to no more than the peer's receive buffer */
-	pe = atomic_read(&mdev->rs_pending_cnt);
-	if ((pe + number) > mx) {
-		number = mx - pe;
-	}
-
 	for (i = 0; i < number; i++) {
 		/* Stop generating RS requests, when half of the send buffer is filled */
 		mutex_lock(&mdev->data.mutex);
@@ -588,16 +558,16 @@ next_sector:
 		size = BM_BLOCK_SIZE;
 		bit  = drbd_bm_find_next(mdev, mdev->bm_resync_fo);
 
-		if (bit == -1UL) {
+		if (bit == DRBD_END_OF_BITMAP) {
 			mdev->bm_resync_fo = drbd_bm_bits(mdev);
-			mdev->resync_work.cb = w_resync_inactive;
 			put_ldev(mdev);
 			return 1;
 		}
 
 		sector = BM_BIT_TO_SECT(bit);
 
-		if (drbd_try_rs_begin_io(mdev, sector)) {
+		if (drbd_rs_should_slow_down(mdev, sector) ||
+		    drbd_try_rs_begin_io(mdev, sector)) {
 			mdev->bm_resync_fo = bit;
 			goto requeue;
 		}
@@ -608,7 +578,7 @@ next_sector:
 			goto next_sector;
 		}
 
-#if DRBD_MAX_SEGMENT_SIZE > BM_BLOCK_SIZE
+#if DRBD_MAX_BIO_SIZE > BM_BLOCK_SIZE
 		/* try to find some adjacent bits.
 		 * we stop if we have already the maximum req size.
 		 *
@@ -618,7 +588,7 @@ next_sector:
 		align = 1;
 		rollback_i = i;
 		for (;;) {
-			if (size + BM_BLOCK_SIZE > max_segment_size)
+			if (size + BM_BLOCK_SIZE > max_bio_size)
 				break;
 
 			/* Be always aligned */
@@ -685,7 +655,6 @@ next_sector:
 		 * resync data block, and the last bit is cleared.
 		 * until then resync "work" is "inactive" ...
 		 */
-		mdev->resync_work.cb = w_resync_inactive;
 		put_ldev(mdev);
 		return 1;
 	}
@@ -706,27 +675,18 @@ static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int ca
 	if (unlikely(cancel))
 		return 1;
 
-	if (unlikely(mdev->state.conn < C_CONNECTED)) {
-		dev_err(DEV, "Confused in w_make_ov_request()! cstate < Connected");
-		return 0;
-	}
-
-	number = SLEEP_TIME*mdev->sync_conf.rate / ((BM_BLOCK_SIZE/1024)*HZ);
-	if (atomic_read(&mdev->rs_pending_cnt) > number)
-		goto requeue;
-
-	number -= atomic_read(&mdev->rs_pending_cnt);
+	number = drbd_rs_number_requests(mdev);
 
 	sector = mdev->ov_position;
 	for (i = 0; i < number; i++) {
 		if (sector >= capacity) {
-			mdev->resync_work.cb = w_resync_inactive;
 			return 1;
 		}
 
 		size = BM_BLOCK_SIZE;
 
-		if (drbd_try_rs_begin_io(mdev, sector)) {
+		if (drbd_rs_should_slow_down(mdev, sector) ||
+		    drbd_try_rs_begin_io(mdev, sector)) {
 			mdev->ov_position = sector;
 			goto requeue;
 		}
@@ -744,11 +704,33 @@ static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int ca
 	mdev->ov_position = sector;
 
  requeue:
+	mdev->rs_in_flight += (i << (BM_BLOCK_SHIFT - 9));
 	mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
 	return 1;
 }
 
 
+void start_resync_timer_fn(unsigned long data)
+{
+	struct drbd_conf *mdev = (struct drbd_conf *) data;
+
+	drbd_queue_work(&mdev->data.work, &mdev->start_resync_work);
+}
+
+int w_start_resync(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	if (atomic_read(&mdev->unacked_cnt) || atomic_read(&mdev->rs_pending_cnt)) {
+		dev_warn(DEV, "w_start_resync later...\n");
+		mdev->start_resync_timer.expires = jiffies + HZ/10;
+		add_timer(&mdev->start_resync_timer);
+		return 1;
+	}
+
+	drbd_start_resync(mdev, C_SYNC_SOURCE);
+	clear_bit(AHEAD_TO_SYNC_SOURCE, &mdev->current_epoch->flags);
+	return 1;
+}
+
 int w_ov_finished(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 {
 	kfree(w);
@@ -782,6 +764,7 @@ int drbd_resync_finished(struct drbd_conf *mdev)
 	union drbd_state os, ns;
 	struct drbd_work *w;
 	char *khelper_cmd = NULL;
+	int verify_done = 0;
 
 	/* Remove all elements from the resync LRU. Since future actions
 	 * might set bits in the (main) bitmap, then the entries in the
@@ -792,9 +775,7 @@ int drbd_resync_finished(struct drbd_conf *mdev)
 		 * queue (or even the read operations for those packets
 		 * is not finished by now).   Retry in 100ms. */
 
-		drbd_kick_lo(mdev);
-		__set_current_state(TASK_INTERRUPTIBLE);
-		schedule_timeout(HZ / 10);
+		schedule_timeout_interruptible(HZ / 10);
 		w = kmalloc(sizeof(struct drbd_work), GFP_ATOMIC);
 		if (w) {
 			w->cb = w_resync_finished;
@@ -819,6 +800,8 @@ int drbd_resync_finished(struct drbd_conf *mdev)
 	spin_lock_irq(&mdev->req_lock);
 	os = mdev->state;
 
+	verify_done = (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T);
+
 	/* This protects us against multiple calls (that can happen in the presence
 	   of application IO), and against connectivity loss just before we arrive here. */
 	if (os.conn <= C_CONNECTED)
@@ -828,8 +811,7 @@ int drbd_resync_finished(struct drbd_conf *mdev)
 	ns.conn = C_CONNECTED;
 
 	dev_info(DEV, "%s done (total %lu sec; paused %lu sec; %lu K/sec)\n",
-	     (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) ?
-	     "Online verify " : "Resync",
+	     verify_done ? "Online verify " : "Resync",
 	     dt + mdev->rs_paused, mdev->rs_paused, dbdt);
 
 	n_oos = drbd_bm_total_weight(mdev);
@@ -887,14 +869,18 @@ int drbd_resync_finished(struct drbd_conf *mdev)
 			}
 		}
 
-		drbd_uuid_set_bm(mdev, 0UL);
-
-		if (mdev->p_uuid) {
-			/* Now the two UUID sets are equal, update what we
-			 * know of the peer. */
-			int i;
-			for (i = UI_CURRENT ; i <= UI_HISTORY_END ; i++)
-				mdev->p_uuid[i] = mdev->ldev->md.uuid[i];
+		if (!(os.conn == C_VERIFY_S || os.conn == C_VERIFY_T)) {
+			/* for verify runs, we don't update uuids here,
+			 * so there would be nothing to report. */
+			drbd_uuid_set_bm(mdev, 0UL);
+			drbd_print_uuids(mdev, "updated UUIDs");
+			if (mdev->p_uuid) {
+				/* Now the two UUID sets are equal, update what we
+				 * know of the peer. */
+				int i;
+				for (i = UI_CURRENT ; i <= UI_HISTORY_END ; i++)
+					mdev->p_uuid[i] = mdev->ldev->md.uuid[i];
+			}
 		}
 	}
 
@@ -906,15 +892,11 @@ out:
 	mdev->rs_total  = 0;
 	mdev->rs_failed = 0;
 	mdev->rs_paused = 0;
-	mdev->ov_start_sector = 0;
+	if (verify_done)
+		mdev->ov_start_sector = 0;
 
 	drbd_md_sync(mdev);
 
-	if (test_and_clear_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags)) {
-		dev_info(DEV, "Writing the whole bitmap\n");
-		drbd_queue_bitmap_io(mdev, &drbd_bm_write, NULL, "write from resync_finished");
-	}
-
 	if (khelper_cmd)
 		drbd_khelper(mdev, khelper_cmd);
 
@@ -995,7 +977,9 @@ int w_e_end_rsdata_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 		put_ldev(mdev);
 	}
 
-	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
+	if (mdev->state.conn == C_AHEAD) {
+		ok = drbd_send_ack(mdev, P_RS_CANCEL, e);
+	} else if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		if (likely(mdev->state.pdsk >= D_INCONSISTENT)) {
 			inc_rs_pending(mdev);
 			ok = drbd_send_block(mdev, P_RS_DATA_REPLY, e);
@@ -1097,25 +1081,27 @@ int w_e_end_ov_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 	if (unlikely(cancel))
 		goto out;
 
-	if (unlikely((e->flags & EE_WAS_ERROR) != 0))
-		goto out;
-
 	digest_size = crypto_hash_digestsize(mdev->verify_tfm);
-	/* FIXME if this allocation fails, online verify will not terminate! */
 	digest = kmalloc(digest_size, GFP_NOIO);
-	if (digest) {
-		drbd_csum_ee(mdev, mdev->verify_tfm, e, digest);
-		inc_rs_pending(mdev);
-		ok = drbd_send_drequest_csum(mdev, e->sector, e->size,
-					     digest, digest_size, P_OV_REPLY);
-		if (!ok)
-			dec_rs_pending(mdev);
-		kfree(digest);
+	if (!digest) {
+		ok = 0;	/* terminate the connection in case the allocation failed */
+		goto out;
 	}
 
+	if (likely(!(e->flags & EE_WAS_ERROR)))
+		drbd_csum_ee(mdev, mdev->verify_tfm, e, digest);
+	else
+		memset(digest, 0, digest_size);
+
+	inc_rs_pending(mdev);
+	ok = drbd_send_drequest_csum(mdev, e->sector, e->size,
+				     digest, digest_size, P_OV_REPLY);
+	if (!ok)
+		dec_rs_pending(mdev);
+	kfree(digest);
+
 out:
 	drbd_free_ee(mdev, e);
-
 	dec_unacked(mdev);
 
 	return ok;
@@ -1130,7 +1116,6 @@ void drbd_ov_oos_found(struct drbd_conf *mdev, sector_t sector, int size)
 		mdev->ov_last_oos_size = size>>9;
 	}
 	drbd_set_out_of_sync(mdev, sector, size);
-	set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
 }
 
 int w_e_end_ov_reply(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
@@ -1166,10 +1151,6 @@ int w_e_end_ov_reply(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 			eq = !memcmp(digest, di->digest, digest_size);
 			kfree(digest);
 		}
-	} else {
-		ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
-		if (__ratelimit(&drbd_ratelimit_state))
-			dev_err(DEV, "Sending NegDReply. I guess it gets messy.\n");
 	}
 
 	dec_unacked(mdev);
@@ -1183,7 +1164,13 @@ int w_e_end_ov_reply(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 
 	drbd_free_ee(mdev, e);
 
-	if (--mdev->ov_left == 0) {
+	--mdev->ov_left;
+
+	/* let's advance progress step marks only for every other megabyte */
+	if ((mdev->ov_left & 0x200) == 0x200)
+		drbd_advance_rs_marks(mdev, mdev->ov_left);
+
+	if (mdev->ov_left == 0) {
 		ov_oos_print(mdev);
 		drbd_resync_finished(mdev);
 	}
@@ -1236,6 +1223,22 @@ int w_send_write_hint(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 	return drbd_send_short_cmd(mdev, P_UNPLUG_REMOTE);
 }
 
+int w_send_oos(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	struct drbd_request *req = container_of(w, struct drbd_request, w);
+	int ok;
+
+	if (unlikely(cancel)) {
+		req_mod(req, send_canceled);
+		return 1;
+	}
+
+	ok = drbd_send_oos(mdev, req);
+	req_mod(req, oos_handed_to_network);
+
+	return ok;
+}
+
 /**
  * w_send_dblock() - Worker callback to send a P_DATA packet in order to mirror a write request
  * @mdev:	DRBD device.
@@ -1431,6 +1434,17 @@ int drbd_alter_sa(struct drbd_conf *mdev, int na)
 	return retcode;
 }
 
+void drbd_rs_controller_reset(struct drbd_conf *mdev)
+{
+	atomic_set(&mdev->rs_sect_in, 0);
+	atomic_set(&mdev->rs_sect_ev, 0);
+	mdev->rs_in_flight = 0;
+	mdev->rs_planed = 0;
+	spin_lock(&mdev->peer_seq_lock);
+	fifo_set(&mdev->rs_plan_s, 0);
+	spin_unlock(&mdev->peer_seq_lock);
+}
+
 /**
  * drbd_start_resync() - Start the resync process
  * @mdev:	DRBD device.
@@ -1444,13 +1458,18 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 	union drbd_state ns;
 	int r;
 
-	if (mdev->state.conn >= C_SYNC_SOURCE) {
+	if (mdev->state.conn >= C_SYNC_SOURCE && mdev->state.conn < C_AHEAD) {
 		dev_err(DEV, "Resync already running!\n");
 		return;
 	}
 
-	/* In case a previous resync run was aborted by an IO error/detach on the peer. */
-	drbd_rs_cancel_all(mdev);
+	if (mdev->state.conn < C_AHEAD) {
+		/* In case a previous resync run was aborted by an IO error/detach on the peer. */
+		drbd_rs_cancel_all(mdev);
+		/* This should be done when we abort the resync. We definitely do not
+		   want to have this for connections going back and forth between
+		   Ahead/Behind and SyncSource/SyncTarget */
+	}
 
 	if (side == C_SYNC_TARGET) {
 		/* Since application IO was locked out during C_WF_BITMAP_T and
@@ -1464,6 +1483,20 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
 			return;
 		}
+	} else /* C_SYNC_SOURCE */ {
+		r = drbd_khelper(mdev, "before-resync-source");
+		r = (r >> 8) & 0xff;
+		if (r > 0) {
+			if (r == 3) {
+				dev_info(DEV, "before-resync-source handler returned %d, "
+					 "ignoring. Old userland tools?", r);
+			} else {
+				dev_info(DEV, "before-resync-source handler returned %d, "
+					 "dropping connection.\n", r);
+				drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+				return;
+			}
+		}
 	}
 
 	drbd_state_lock(mdev);
@@ -1473,18 +1506,6 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 		return;
 	}
 
-	if (side == C_SYNC_TARGET) {
-		mdev->bm_resync_fo = 0;
-	} else /* side == C_SYNC_SOURCE */ {
-		u64 uuid;
-
-		get_random_bytes(&uuid, sizeof(u64));
-		drbd_uuid_set(mdev, UI_BITMAP, uuid);
-		drbd_send_sync_uuid(mdev, uuid);
-
-		D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
-	}
-
 	write_lock_irq(&global_state_lock);
 	ns = mdev->state;
 
@@ -1522,13 +1543,24 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 		_drbd_pause_after(mdev);
 	}
 	write_unlock_irq(&global_state_lock);
-	put_ldev(mdev);
 
 	if (r == SS_SUCCESS) {
 		dev_info(DEV, "Began resync as %s (will sync %lu KB [%lu bits set]).\n",
 		     drbd_conn_str(ns.conn),
 		     (unsigned long) mdev->rs_total << (BM_BLOCK_SHIFT-10),
 		     (unsigned long) mdev->rs_total);
+		if (side == C_SYNC_TARGET)
+			mdev->bm_resync_fo = 0;
+
+		/* Since protocol 96, we must serialize drbd_gen_and_send_sync_uuid
+		 * with w_send_oos, or the sync target will get confused as to
+		 * how much bits to resync.  We cannot do that always, because for an
+		 * empty resync and protocol < 95, we need to do it here, as we call
+		 * drbd_resync_finished from here in that case.
+		 * We drbd_gen_and_send_sync_uuid here for protocol < 96,
+		 * and from after_state_ch otherwise. */
+		if (side == C_SYNC_SOURCE && mdev->agreed_pro_version < 96)
+			drbd_gen_and_send_sync_uuid(mdev);
 
 		if (mdev->agreed_pro_version < 95 && mdev->rs_total == 0) {
 			/* This still has a race (about when exactly the peers
@@ -1548,13 +1580,7 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 			drbd_resync_finished(mdev);
 		}
 
-		atomic_set(&mdev->rs_sect_in, 0);
-		atomic_set(&mdev->rs_sect_ev, 0);
-		mdev->rs_in_flight = 0;
-		mdev->rs_planed = 0;
-		spin_lock(&mdev->peer_seq_lock);
-		fifo_set(&mdev->rs_plan_s, 0);
-		spin_unlock(&mdev->peer_seq_lock);
+		drbd_rs_controller_reset(mdev);
 		/* ns.conn may already be != mdev->state.conn,
 		 * we may have been paused in between, or become paused until
 		 * the timer triggers.
@@ -1564,6 +1590,7 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 
 		drbd_md_sync(mdev);
 	}
+	put_ldev(mdev);
 	drbd_state_unlock(mdev);
 }
 
diff --git a/drivers/block/drbd/drbd_wrappers.h b/drivers/block/drbd/drbd_wrappers.h
index defdb5013ea..151f1a37478 100644
--- a/drivers/block/drbd/drbd_wrappers.h
+++ b/drivers/block/drbd/drbd_wrappers.h
@@ -39,30 +39,12 @@ static inline void drbd_generic_make_request(struct drbd_conf *mdev,
 		return;
 	}
 
-	if (FAULT_ACTIVE(mdev, fault_type))
+	if (drbd_insert_fault(mdev, fault_type))
 		bio_endio(bio, -EIO);
 	else
 		generic_make_request(bio);
 }
 
-static inline void drbd_plug_device(struct drbd_conf *mdev)
-{
-	struct request_queue *q;
-	q = bdev_get_queue(mdev->this_bdev);
-
-	spin_lock_irq(q->queue_lock);
-
-/* XXX the check on !blk_queue_plugged is redundant,
- * implicitly checked in blk_plug_device */
-
-	if (!blk_queue_plugged(q)) {
-		blk_plug_device(q);
-		del_timer(&q->unplug_timer);
-		/* unplugging should not happen automatically... */
-	}
-	spin_unlock_irq(q->queue_lock);
-}
-
 static inline int drbd_crypto_is_hash(struct crypto_tfm *tfm)
 {
         return (crypto_tfm_alg_type(tfm) & CRYPTO_ALG_TYPE_HASH_MASK)