Merge branch 'drbd-8.4_ed6' into for-3.8-drivers-drbd-8.4_ed6

1 files changed, 755 insertions, 814 deletions

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 135ea76ed50..f58a4a4b4df 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -31,6 +31,8 @@
 #include "drbd_req.h"
 
 
+static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size);
+
 /* Update disk stats at start of I/O request */
 static void _drbd_start_io_acct(struct drbd_conf *mdev, struct drbd_request *req, struct bio *bio)
 {
@@ -40,6 +42,8 @@ static void _drbd_start_io_acct(struct drbd_conf *mdev, struct drbd_request *req
 	part_round_stats(cpu, &mdev->vdisk->part0);
 	part_stat_inc(cpu, &mdev->vdisk->part0, ios[rw]);
 	part_stat_add(cpu, &mdev->vdisk->part0, sectors[rw], bio_sectors(bio));
+	(void) cpu; /* The macro invocations above want the cpu argument, I do not like
+		       the compiler warning about cpu only assigned but never used... */
 	part_inc_in_flight(&mdev->vdisk->part0, rw);
 	part_stat_unlock();
 }
@@ -57,9 +61,51 @@ static void _drbd_end_io_acct(struct drbd_conf *mdev, struct drbd_request *req)
 	part_stat_unlock();
 }
 
-static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const int rw)
+static struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
+					       struct bio *bio_src)
+{
+	struct drbd_request *req;
+
+	req = mempool_alloc(drbd_request_mempool, GFP_NOIO);
+	if (!req)
+		return NULL;
+
+	drbd_req_make_private_bio(req, bio_src);
+	req->rq_state    = bio_data_dir(bio_src) == WRITE ? RQ_WRITE : 0;
+	req->w.mdev      = mdev;
+	req->master_bio  = bio_src;
+	req->epoch       = 0;
+
+	drbd_clear_interval(&req->i);
+	req->i.sector     = bio_src->bi_sector;
+	req->i.size      = bio_src->bi_size;
+	req->i.local = true;
+	req->i.waiting = false;
+
+	INIT_LIST_HEAD(&req->tl_requests);
+	INIT_LIST_HEAD(&req->w.list);
+
+	/* one reference to be put by __drbd_make_request */
+	atomic_set(&req->completion_ref, 1);
+	/* one kref as long as completion_ref > 0 */
+	kref_init(&req->kref);
+	return req;
+}
+
+void drbd_req_destroy(struct kref *kref)
 {
-	const unsigned long s = req->rq_state;
+	struct drbd_request *req = container_of(kref, struct drbd_request, kref);
+	struct drbd_conf *mdev = req->w.mdev;
+	const unsigned s = req->rq_state;
+
+	if ((req->master_bio && !(s & RQ_POSTPONED)) ||
+		atomic_read(&req->completion_ref) ||
+		(s & RQ_LOCAL_PENDING) ||
+		((s & RQ_NET_MASK) && !(s & RQ_NET_DONE))) {
+		dev_err(DEV, "drbd_req_destroy: Logic BUG rq_state = 0x%x, completion_ref = %d\n",
+				s, atomic_read(&req->completion_ref));
+		return;
+	}
 
 	/* remove it from the transfer log.
 	 * well, only if it had been there in the first
@@ -67,24 +113,33 @@ static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const
 	 * and never sent), it should still be "empty" as
 	 * initialized in drbd_req_new(), so we can list_del() it
 	 * here unconditionally */
-	list_del(&req->tl_requests);
+	list_del_init(&req->tl_requests);
 
 	/* if it was a write, we may have to set the corresponding
 	 * bit(s) out-of-sync first. If it had a local part, we need to
 	 * release the reference to the activity log. */
-	if (rw == WRITE) {
+	if (s & RQ_WRITE) {
 		/* Set out-of-sync unless both OK flags are set
 		 * (local only or remote failed).
 		 * Other places where we set out-of-sync:
 		 * READ with local io-error */
-		if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
-			drbd_set_out_of_sync(mdev, req->sector, req->size);
 
-		if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
-			drbd_set_in_sync(mdev, req->sector, req->size);
+		/* There is a special case:
+		 * we may notice late that IO was suspended,
+		 * and postpone, or schedule for retry, a write,
+		 * before it even was submitted or sent.
+		 * In that case we do not want to touch the bitmap at all.
+		 */
+		if ((s & (RQ_POSTPONED|RQ_LOCAL_MASK|RQ_NET_MASK)) != RQ_POSTPONED) {
+			if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
+				drbd_set_out_of_sync(mdev, req->i.sector, req->i.size);
+
+			if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
+				drbd_set_in_sync(mdev, req->i.sector, req->i.size);
+		}
 
 		/* one might be tempted to move the drbd_al_complete_io
-		 * to the local io completion callback drbd_endio_pri.
+		 * to the local io completion callback drbd_request_endio.
 		 * but, if this was a mirror write, we may only
 		 * drbd_al_complete_io after this is RQ_NET_DONE,
 		 * otherwise the extent could be dropped from the al
@@ -93,109 +148,35 @@ static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const
 		 * but after the extent has been dropped from the al,
 		 * we would forget to resync the corresponding extent.
 		 */
-		if (s & RQ_LOCAL_MASK) {
+		if (s & RQ_IN_ACT_LOG) {
 			if (get_ldev_if_state(mdev, D_FAILED)) {
-				if (s & RQ_IN_ACT_LOG)
-					drbd_al_complete_io(mdev, req->sector);
+				drbd_al_complete_io(mdev, &req->i);
 				put_ldev(mdev);
 			} else if (__ratelimit(&drbd_ratelimit_state)) {
-				dev_warn(DEV, "Should have called drbd_al_complete_io(, %llu), "
-				     "but my Disk seems to have failed :(\n",
-				     (unsigned long long) req->sector);
+				dev_warn(DEV, "Should have called drbd_al_complete_io(, %llu, %u), "
+					 "but my Disk seems to have failed :(\n",
+					 (unsigned long long) req->i.sector, req->i.size);
 			}
 		}
 	}
 
-	drbd_req_free(req);
+	mempool_free(req, drbd_request_mempool);
 }
 
-static void queue_barrier(struct drbd_conf *mdev)
-{
-	struct drbd_tl_epoch *b;
-
-	/* We are within the req_lock. Once we queued the barrier for sending,
-	 * we set the CREATE_BARRIER bit. It is cleared as soon as a new
-	 * barrier/epoch object is added. This is the only place this bit is
-	 * set. It indicates that the barrier for this epoch is already queued,
-	 * and no new epoch has been created yet. */
-	if (drbd_test_flag(mdev, CREATE_BARRIER))
-		return;
-
-	b = mdev->newest_tle;
-	b->w.cb = w_send_barrier;
-	/* inc_ap_pending done here, so we won't
-	 * get imbalanced on connection loss.
-	 * dec_ap_pending will be done in got_BarrierAck
-	 * or (on connection loss) in tl_clear.  */
-	inc_ap_pending(mdev);
-	drbd_queue_work(&mdev->data.work, &b->w);
-	drbd_set_flag(mdev, CREATE_BARRIER);
+static void wake_all_senders(struct drbd_tconn *tconn) {
+	wake_up(&tconn->sender_work.q_wait);
 }
 
-static void _about_to_complete_local_write(struct drbd_conf *mdev,
-	struct drbd_request *req)
+/* must hold resource->req_lock */
+static void start_new_tl_epoch(struct drbd_tconn *tconn)
 {
-	const unsigned long s = req->rq_state;
-	struct drbd_request *i;
-	struct drbd_epoch_entry *e;
-	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.
-	 * 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);
-
-	/* we need to do the conflict detection stuff,
-	 * if we have the ee_hash (two_primaries) and
-	 * this has been on the network */
-	if ((s & RQ_NET_DONE) && mdev->ee_hash != NULL) {
-		const sector_t sector = req->sector;
-		const int size = req->size;
-
-		/* ASSERT:
-		 * there must be no conflicting requests, since
-		 * they must have been failed on the spot */
-#define OVERLAPS overlaps(sector, size, i->sector, i->size)
-		slot = tl_hash_slot(mdev, sector);
-		hlist_for_each_entry(i, n, slot, collision) {
-			if (OVERLAPS) {
-				dev_alert(DEV, "LOGIC BUG: completed: %p %llus +%u; "
-				      "other: %p %llus +%u\n",
-				      req, (unsigned long long)sector, size,
-				      i, (unsigned long long)i->sector, i->size);
-			}
-		}
+	/* no point closing an epoch, if it is empty, anyways. */
+	if (tconn->current_tle_writes == 0)
+		return;
 
-		/* maybe "wake" those conflicting epoch entries
-		 * that wait for this request to finish.
-		 *
-		 * currently, there can be only _one_ such ee
-		 * (well, or some more, which would be pending
-		 * P_DISCARD_ACK not yet sent by the asender...),
-		 * since we block the receiver thread upon the
-		 * first conflict detection, which will wait on
-		 * misc_wait.  maybe we want to assert that?
-		 *
-		 * anyways, if we found one,
-		 * we just have to do a wake_up.  */
-#undef OVERLAPS
-#define OVERLAPS overlaps(sector, size, e->sector, e->size)
-		slot = ee_hash_slot(mdev, req->sector);
-		hlist_for_each_entry(e, n, slot, collision) {
-			if (OVERLAPS) {
-				wake_up(&mdev->misc_wait);
-				break;
-			}
-		}
-	}
-#undef OVERLAPS
+	tconn->current_tle_writes = 0;
+	atomic_inc(&tconn->current_tle_nr);
+	wake_all_senders(tconn);
 }
 
 void complete_master_bio(struct drbd_conf *mdev,
@@ -205,17 +186,33 @@ void complete_master_bio(struct drbd_conf *mdev,
 	dec_ap_bio(mdev);
 }
 
+
+static void drbd_remove_request_interval(struct rb_root *root,
+					 struct drbd_request *req)
+{
+	struct drbd_conf *mdev = req->w.mdev;
+	struct drbd_interval *i = &req->i;
+
+	drbd_remove_interval(root, i);
+
+	/* Wake up any processes waiting for this request to complete.  */
+	if (i->waiting)
+		wake_up(&mdev->misc_wait);
+}
+
 /* Helper for __req_mod().
  * Set m->bio to the master bio, if it is fit to be completed,
  * or leave it alone (it is initialized to NULL in __req_mod),
  * if it has already been completed, or cannot be completed yet.
  * If m->bio is set, the error status to be returned is placed in m->error.
  */
-void _req_may_be_done(struct drbd_request *req, struct bio_and_error *m)
+static
+void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
 {
-	const unsigned long s = req->rq_state;
-	struct drbd_conf *mdev = req->mdev;
-	int rw = req->rq_state & RQ_WRITE ? WRITE : READ;
+	const unsigned s = req->rq_state;
+	struct drbd_conf *mdev = req->w.mdev;
+	int rw;
+	int error, ok;
 
 	/* we must not complete the master bio, while it is
 	 *	still being processed by _drbd_send_zc_bio (drbd_send_dblock)
@@ -226,178 +223,219 @@ void _req_may_be_done(struct drbd_request *req, struct bio_and_error *m)
 	 *	the receiver,
 	 *	the bio_endio completion callbacks.
 	 */
-	if (s & RQ_NET_QUEUED)
-		return;
-	if (s & RQ_NET_PENDING)
+	if ((s & RQ_LOCAL_PENDING && !(s & RQ_LOCAL_ABORTED)) ||
+	    (s & RQ_NET_QUEUED) || (s & RQ_NET_PENDING) ||
+	    (s & RQ_COMPLETION_SUSP)) {
+		dev_err(DEV, "drbd_req_complete: Logic BUG rq_state = 0x%x\n", s);
 		return;
-	if (s & RQ_LOCAL_PENDING && !(s & RQ_LOCAL_ABORTED))
+	}
+
+	if (!req->master_bio) {
+		dev_err(DEV, "drbd_req_complete: Logic BUG, master_bio == NULL!\n");
 		return;
+	}
 
-	if (req->master_bio) {
-		/* this is data_received (remote read)
-		 * or protocol C P_WRITE_ACK
-		 * or protocol B P_RECV_ACK
-		 * or protocol A "handed_over_to_network" (SendAck)
-		 * or canceled or failed,
-		 * or killed from the transfer log due to connection loss.
-		 */
+	rw = bio_rw(req->master_bio);
 
-		/*
-		 * figure out whether to report success or failure.
-		 *
-		 * report success when at least one of the operations succeeded.
-		 * or, to put the other way,
-		 * only report failure, when both operations failed.
-		 *
-		 * what to do about the failures is handled elsewhere.
-		 * what we need to do here is just: complete the master_bio.
-		 *
-		 * local completion error, if any, has been stored as ERR_PTR
-		 * in private_bio within drbd_endio_pri.
-		 */
-		int ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
-		int error = PTR_ERR(req->private_bio);
+	/*
+	 * figure out whether to report success or failure.
+	 *
+	 * report success when at least one of the operations succeeded.
+	 * or, to put the other way,
+	 * only report failure, when both operations failed.
+	 *
+	 * what to do about the failures is handled elsewhere.
+	 * what we need to do here is just: complete the master_bio.
+	 *
+	 * local completion error, if any, has been stored as ERR_PTR
+	 * in private_bio within drbd_request_endio.
+	 */
+	ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
+	error = PTR_ERR(req->private_bio);
 
-		/* remove the request from the conflict detection
-		 * respective block_id verification hash */
-		if (!hlist_unhashed(&req->collision))
-			hlist_del(&req->collision);
-		else
-			D_ASSERT((s & (RQ_NET_MASK & ~RQ_NET_DONE)) == 0);
+	/* remove the request from the conflict detection
+	 * respective block_id verification hash */
+	if (!drbd_interval_empty(&req->i)) {
+		struct rb_root *root;
 
-		/* for writes we need to do some extra housekeeping */
 		if (rw == WRITE)
-			_about_to_complete_local_write(mdev, req);
+			root = &mdev->write_requests;
+		else
+			root = &mdev->read_requests;
+		drbd_remove_request_interval(root, req);
+	} else if (!(s & RQ_POSTPONED))
+		D_ASSERT((s & (RQ_NET_MASK & ~RQ_NET_DONE)) == 0);
 
-		/* Update disk stats */
-		_drbd_end_io_acct(mdev, req);
+	/* Before we can signal completion to the upper layers,
+	 * we may need to close the current transfer log epoch.
+	 * We are within the request lock, so we can simply compare
+	 * the request epoch number with the current transfer log
+	 * epoch number.  If they match, increase the current_tle_nr,
+	 * and reset the transfer log epoch write_cnt.
+	 */
+	if (rw == WRITE &&
+	    req->epoch == atomic_read(&mdev->tconn->current_tle_nr))
+		start_new_tl_epoch(mdev->tconn);
+
+	/* Update disk stats */
+	_drbd_end_io_acct(mdev, req);
+
+	/* If READ failed,
+	 * have it be pushed back to the retry work queue,
+	 * so it will re-enter __drbd_make_request(),
+	 * and be re-assigned to a suitable local or remote path,
+	 * or failed if we do not have access to good data anymore.
+	 *
+	 * Unless it was failed early by __drbd_make_request(),
+	 * because no path was available, in which case
+	 * it was not even added to the transfer_log.
+	 *
+	 * READA may fail, and will not be retried.
+	 *
+	 * WRITE should have used all available paths already.
+	 */
+	if (!ok && rw == READ && !list_empty(&req->tl_requests))
+		req->rq_state |= RQ_POSTPONED;
 
+	if (!(req->rq_state & RQ_POSTPONED)) {
 		m->error = ok ? 0 : (error ?: -EIO);
 		m->bio = req->master_bio;
 		req->master_bio = NULL;
 	}
+}
 
-	if (s & RQ_LOCAL_PENDING)
-		return;
+static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
+{
+	struct drbd_conf *mdev = req->w.mdev;
+	D_ASSERT(m || (req->rq_state & RQ_POSTPONED));
+
+	if (!atomic_sub_and_test(put, &req->completion_ref))
+		return 0;
 
-	if ((s & RQ_NET_MASK) == 0 || (s & RQ_NET_DONE)) {
-		/* this is disconnected (local only) operation,
-		 * or protocol C P_WRITE_ACK,
-		 * or protocol A or B P_BARRIER_ACK,
-		 * or killed from the transfer log due to connection loss. */
-		_req_is_done(mdev, req, rw);
+	drbd_req_complete(req, m);
+
+	if (req->rq_state & RQ_POSTPONED) {
+		/* don't destroy the req object just yet,
+		 * but queue it for retry */
+		drbd_restart_request(req);
+		return 0;
 	}
-	/* else: network part and not DONE yet. that is
-	 * protocol A or B, barrier ack still pending... */
+
+	return 1;
 }
 
-static void _req_may_be_done_not_susp(struct drbd_request *req, struct bio_and_error *m)
+/* I'd like this to be the only place that manipulates
+ * req->completion_ref and req->kref. */
+static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
+		int clear, int set)
 {
-	struct drbd_conf *mdev = req->mdev;
+	struct drbd_conf *mdev = req->w.mdev;
+	unsigned s = req->rq_state;
+	int c_put = 0;
+	int k_put = 0;
 
-	if (!is_susp(mdev->state))
-		_req_may_be_done(req, m);
-}
+	if (drbd_suspended(mdev) && !((s | clear) & RQ_COMPLETION_SUSP))
+		set |= RQ_COMPLETION_SUSP;
 
-/*
- * checks whether there was an overlapping request
- * or ee already registered.
- *
- * if so, return 1, in which case this request is completed on the spot,
- * without ever being submitted or send.
- *
- * return 0 if it is ok to submit this request.
- *
- * NOTE:
- * paranoia: assume something above us is broken, and issues different write
- * requests for the same block simultaneously...
- *
- * To ensure these won't be reordered differently on both nodes, resulting in
- * diverging data sets, we discard the later one(s). Not that this is supposed
- * to happen, but this is the rationale why we also have to check for
- * conflicting requests with local origin, and why we have to do so regardless
- * of whether we allowed multiple primaries.
- *
- * BTW, in case we only have one primary, the ee_hash is empty anyways, and the
- * second hlist_for_each_entry becomes a noop. This is even simpler than to
- * grab a reference on the net_conf, and check for the two_primaries flag...
- */
-static int _req_conflicts(struct drbd_request *req)
-{
-	struct drbd_conf *mdev = req->mdev;
-	const sector_t sector = req->sector;
-	const int size = req->size;
-	struct drbd_request *i;
-	struct drbd_epoch_entry *e;
-	struct hlist_node *n;
-	struct hlist_head *slot;
+	/* apply */
 
-	D_ASSERT(hlist_unhashed(&req->collision));
+	req->rq_state &= ~clear;
+	req->rq_state |= set;
 
-	if (!get_net_conf(mdev))
-		return 0;
+	/* no change? */
+	if (req->rq_state == s)
+		return;
 
-	/* BUG_ON */
-	ERR_IF (mdev->tl_hash_s == 0)
-		goto out_no_conflict;
-	BUG_ON(mdev->tl_hash == NULL);
-
-#define OVERLAPS overlaps(i->sector, i->size, sector, size)
-	slot = tl_hash_slot(mdev, sector);
-	hlist_for_each_entry(i, n, slot, collision) {
-		if (OVERLAPS) {
-			dev_alert(DEV, "%s[%u] Concurrent local write detected! "
-			      "[DISCARD L] new: %llus +%u; "
-			      "pending: %llus +%u\n",
-			      current->comm, current->pid,
-			      (unsigned long long)sector, size,
-			      (unsigned long long)i->sector, i->size);
-			goto out_conflict;
-		}
+	/* intent: get references */
+
+	if (!(s & RQ_LOCAL_PENDING) && (set & RQ_LOCAL_PENDING))
+		atomic_inc(&req->completion_ref);
+
+	if (!(s & RQ_NET_PENDING) && (set & RQ_NET_PENDING)) {
+		inc_ap_pending(mdev);
+		atomic_inc(&req->completion_ref);
 	}
 
-	if (mdev->ee_hash_s) {
-		/* now, check for overlapping requests with remote origin */
-		BUG_ON(mdev->ee_hash == NULL);
-#undef OVERLAPS
-#define OVERLAPS overlaps(e->sector, e->size, sector, size)
-		slot = ee_hash_slot(mdev, sector);
-		hlist_for_each_entry(e, n, slot, collision) {
-			if (OVERLAPS) {
-				dev_alert(DEV, "%s[%u] Concurrent remote write detected!"
-				      " [DISCARD L] new: %llus +%u; "
-				      "pending: %llus +%u\n",
-				      current->comm, current->pid,
-				      (unsigned long long)sector, size,
-				      (unsigned long long)e->sector, e->size);
-				goto out_conflict;
-			}
-		}
+	if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED))
+		atomic_inc(&req->completion_ref);
+
+	if (!(s & RQ_EXP_BARR_ACK) && (set & RQ_EXP_BARR_ACK))
+		kref_get(&req->kref); /* wait for the DONE */
+
+	if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT))
+		atomic_add(req->i.size >> 9, &mdev->ap_in_flight);
+
+	if (!(s & RQ_COMPLETION_SUSP) && (set & RQ_COMPLETION_SUSP))
+		atomic_inc(&req->completion_ref);
+
+	/* progress: put references */
+
+	if ((s & RQ_COMPLETION_SUSP) && (clear & RQ_COMPLETION_SUSP))
+		++c_put;
+
+	if (!(s & RQ_LOCAL_ABORTED) && (set & RQ_LOCAL_ABORTED)) {
+		D_ASSERT(req->rq_state & RQ_LOCAL_PENDING);
+		/* local completion may still come in later,
+		 * we need to keep the req object around. */
+		kref_get(&req->kref);
+		++c_put;
 	}
-#undef OVERLAPS
 
-out_no_conflict:
-	/* this is like it should be, and what we expected.
-	 * our users do behave after all... */
-	put_net_conf(mdev);
-	return 0;
+	if ((s & RQ_LOCAL_PENDING) && (clear & RQ_LOCAL_PENDING)) {
+		if (req->rq_state & RQ_LOCAL_ABORTED)
+			++k_put;
+		else
+			++c_put;
+	}
 
-out_conflict:
-	put_net_conf(mdev);
-	return 1;
+	if ((s & RQ_NET_PENDING) && (clear & RQ_NET_PENDING)) {
+		dec_ap_pending(mdev);
+		++c_put;
+	}
+
+	if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED))
+		++c_put;
+
+	if ((s & RQ_EXP_BARR_ACK) && !(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
+		if (req->rq_state & RQ_NET_SENT)
+			atomic_sub(req->i.size >> 9, &mdev->ap_in_flight);
+		++k_put;
+	}
+
+	/* potentially complete and destroy */
+
+	if (k_put || c_put) {
+		/* Completion does it's own kref_put.  If we are going to
+		 * kref_sub below, we need req to be still around then. */
+		int at_least = k_put + !!c_put;
+		int refcount = atomic_read(&req->kref.refcount);
+		if (refcount < at_least)
+			dev_err(DEV,
+				"mod_rq_state: Logic BUG: %x -> %x: refcount = %d, should be >= %d\n",
+				s, req->rq_state, refcount, at_least);
+	}
+
+	/* If we made progress, retry conflicting peer requests, if any. */
+	if (req->i.waiting)
+		wake_up(&mdev->misc_wait);
+
+	if (c_put)
+		k_put += drbd_req_put_completion_ref(req, m, c_put);
+	if (k_put)
+		kref_sub(&req->kref, k_put, drbd_req_destroy);
 }
 
 static void drbd_report_io_error(struct drbd_conf *mdev, struct drbd_request *req)
 {
         char b[BDEVNAME_SIZE];
 
-	if (__ratelimit(&drbd_ratelimit_state))
+	if (!__ratelimit(&drbd_ratelimit_state))
 		return;
 
 	dev_warn(DEV, "local %s IO error sector %llu+%u on %s\n",
 			(req->rq_state & RQ_WRITE) ? "WRITE" : "READ",
-			(unsigned long long)req->sector,
-			req->size >> 9,
+			(unsigned long long)req->i.sector,
+			req->i.size >> 9,
 			bdevname(mdev->ldev->backing_bdev, b));
 }
 
@@ -416,9 +454,12 @@ static void drbd_report_io_error(struct drbd_conf *mdev, struct drbd_request *re
 int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		struct bio_and_error *m)
 {
-	struct drbd_conf *mdev = req->mdev;
-	int rv = 0;
-	m->bio = NULL;
+	struct drbd_conf *mdev = req->w.mdev;
+	struct net_conf *nc;
+	int p, rv = 0;
+
+	if (m)
+		m->bio = NULL;
 
 	switch (what) {
 	default:
@@ -427,118 +468,91 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 	/* does not happen...
 	 * initialization done in drbd_req_new
-	case created:
+	case CREATED:
 		break;
 		*/
 
-	case to_be_send: /* via network */
-		/* reached via drbd_make_request_common
+	case TO_BE_SENT: /* via network */
+		/* reached via __drbd_make_request
 		 * and from w_read_retry_remote */
 		D_ASSERT(!(req->rq_state & RQ_NET_MASK));
-		req->rq_state |= RQ_NET_PENDING;
-		inc_ap_pending(mdev);
+		rcu_read_lock();
+		nc = rcu_dereference(mdev->tconn->net_conf);
+		p = nc->wire_protocol;
+		rcu_read_unlock();
+		req->rq_state |=
+			p == DRBD_PROT_C ? RQ_EXP_WRITE_ACK :
+			p == DRBD_PROT_B ? RQ_EXP_RECEIVE_ACK : 0;
+		mod_rq_state(req, m, 0, RQ_NET_PENDING);
 		break;
 
-	case to_be_submitted: /* locally */
-		/* reached via drbd_make_request_common */
+	case TO_BE_SUBMITTED: /* locally */
+		/* reached via __drbd_make_request */
 		D_ASSERT(!(req->rq_state & RQ_LOCAL_MASK));
-		req->rq_state |= RQ_LOCAL_PENDING;
+		mod_rq_state(req, m, 0, RQ_LOCAL_PENDING);
 		break;
 
-	case completed_ok:
+	case COMPLETED_OK:
 		if (req->rq_state & RQ_WRITE)
-			mdev->writ_cnt += req->size>>9;
+			mdev->writ_cnt += req->i.size >> 9;
 		else
-			mdev->read_cnt += req->size>>9;
+			mdev->read_cnt += req->i.size >> 9;
 
-		req->rq_state |= (RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
-		req->rq_state &= ~RQ_LOCAL_PENDING;
-
-		_req_may_be_done_not_susp(req, m);
+		mod_rq_state(req, m, RQ_LOCAL_PENDING,
+				RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
 		break;
 
-	case abort_disk_io:
-		req->rq_state |= RQ_LOCAL_ABORTED;
-		if (req->rq_state & RQ_WRITE)
-			_req_may_be_done_not_susp(req, m);
-		else
-			goto goto_queue_for_net_read;
+	case ABORT_DISK_IO:
+		mod_rq_state(req, m, 0, RQ_LOCAL_ABORTED);
 		break;
 
-	case write_completed_with_error:
-		req->rq_state |= RQ_LOCAL_COMPLETED;
-		req->rq_state &= ~RQ_LOCAL_PENDING;
-
+	case WRITE_COMPLETED_WITH_ERROR:
 		drbd_report_io_error(mdev, req);
 		__drbd_chk_io_error(mdev, DRBD_WRITE_ERROR);
-		_req_may_be_done_not_susp(req, m);
+		mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
 		break;
 
-	case read_ahead_completed_with_error:
-		/* it is legal to fail READA */
-		req->rq_state |= RQ_LOCAL_COMPLETED;
-		req->rq_state &= ~RQ_LOCAL_PENDING;
-		_req_may_be_done_not_susp(req, m);
-		break;
-
-	case read_completed_with_error:
-		drbd_set_out_of_sync(mdev, req->sector, req->size);
-
-		req->rq_state |= RQ_LOCAL_COMPLETED;
-		req->rq_state &= ~RQ_LOCAL_PENDING;
-
-		if (req->rq_state & RQ_LOCAL_ABORTED) {
-			_req_may_be_done(req, m);
-			break;
-		}
-
+	case READ_COMPLETED_WITH_ERROR:
+		drbd_set_out_of_sync(mdev, req->i.sector, req->i.size);
 		drbd_report_io_error(mdev, req);
 		__drbd_chk_io_error(mdev, DRBD_READ_ERROR);
+		/* fall through. */
+	case READ_AHEAD_COMPLETED_WITH_ERROR:
+		/* it is legal to fail READA, no __drbd_chk_io_error in that case. */
+		mod_rq_state(req, m, RQ_LOCAL_PENDING, RQ_LOCAL_COMPLETED);
+		break;
 
-	goto_queue_for_net_read:
-
-		D_ASSERT(!(req->rq_state & RQ_NET_MASK));
-
-		/* no point in retrying if there is no good remote data,
-		 * or we have no connection. */
-		if (mdev->state.pdsk != D_UP_TO_DATE) {
-			_req_may_be_done_not_susp(req, m);
-			break;
-		}
-
-		/* _req_mod(req,to_be_send); oops, recursion... */
-		req->rq_state |= RQ_NET_PENDING;
-		inc_ap_pending(mdev);
-		/* fall through: _req_mod(req,queue_for_net_read); */
-
-	case queue_for_net_read:
+	case QUEUE_FOR_NET_READ:
 		/* READ or READA, and
 		 * no local disk,
 		 * or target area marked as invalid,
 		 * or just got an io-error. */
-		/* from drbd_make_request_common
+		/* from __drbd_make_request
 		 * or from bio_endio during read io-error recovery */
 
-		/* so we can verify the handle in the answer packet
-		 * corresponding hlist_del is in _req_may_be_done() */
-		hlist_add_head(&req->collision, ar_hash_slot(mdev, req->sector));
+		/* So we can verify the handle in the answer packet.
+		 * Corresponding drbd_remove_request_interval is in
+		 * drbd_req_complete() */
+		D_ASSERT(drbd_interval_empty(&req->i));
+		drbd_insert_interval(&mdev->read_requests, &req->i);
 
-		drbd_set_flag(mdev, UNPLUG_REMOTE);
+		set_bit(UNPLUG_REMOTE, &mdev->flags);
 
 		D_ASSERT(req->rq_state & RQ_NET_PENDING);
-		req->rq_state |= RQ_NET_QUEUED;
-		req->w.cb = (req->rq_state & RQ_LOCAL_MASK)
-			? w_read_retry_remote
-			: w_send_read_req;
-		drbd_queue_work(&mdev->data.work, &req->w);
+		D_ASSERT((req->rq_state & RQ_LOCAL_MASK) == 0);
+		mod_rq_state(req, m, 0, RQ_NET_QUEUED);
+		req->w.cb = w_send_read_req;
+		drbd_queue_work(&mdev->tconn->sender_work, &req->w);
 		break;
 
-	case queue_for_net_write:
+	case QUEUE_FOR_NET_WRITE:
 		/* assert something? */
-		/* from drbd_make_request_common only */
+		/* from __drbd_make_request only */
 
-		hlist_add_head(&req->collision, tl_hash_slot(mdev, req->sector));
-		/* corresponding hlist_del is in _req_may_be_done() */
+		/* Corresponding drbd_remove_request_interval is in
+		 * drbd_req_complete() */
+		D_ASSERT(drbd_interval_empty(&req->i));
+		drbd_insert_interval(&mdev->write_requests, &req->i);
 
 		/* NOTE
 		 * In case the req ended up on the transfer log before being
@@ -549,7 +563,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		 *
 		 * _req_add_to_epoch(req); this has to be after the
 		 * _maybe_start_new_epoch(req); which happened in
-		 * drbd_make_request_common, because we now may set the bit
+		 * __drbd_make_request, because we now may set the bit
 		 * again ourselves to close the current epoch.
 		 *
 		 * Add req to the (now) current epoch (barrier). */
@@ -557,204 +571,189 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		/* otherwise we may lose an unplug, which may cause some remote
 		 * io-scheduler timeout to expire, increasing maximum latency,
 		 * hurting performance. */
-		drbd_set_flag(mdev, UNPLUG_REMOTE);
-
-		/* see drbd_make_request_common,
-		 * just after it grabs the req_lock */
-		D_ASSERT(drbd_test_flag(mdev, CREATE_BARRIER) == 0);
-
-		req->epoch = mdev->newest_tle->br_number;
-
-		/* increment size of current epoch */
-		mdev->newest_tle->n_writes++;
+		set_bit(UNPLUG_REMOTE, &mdev->flags);
 
 		/* queue work item to send data */
 		D_ASSERT(req->rq_state & RQ_NET_PENDING);
-		req->rq_state |= RQ_NET_QUEUED;
+		mod_rq_state(req, m, 0, RQ_NET_QUEUED|RQ_EXP_BARR_ACK);
 		req->w.cb =  w_send_dblock;
-		drbd_queue_work(&mdev->data.work, &req->w);
+		drbd_queue_work(&mdev->tconn->sender_work, &req->w);
 
 		/* close the epoch, in case it outgrew the limit */
-		if (mdev->newest_tle->n_writes >= mdev->net_conf->max_epoch_size)
-			queue_barrier(mdev);
+		rcu_read_lock();
+		nc = rcu_dereference(mdev->tconn->net_conf);
+		p = nc->max_epoch_size;
+		rcu_read_unlock();
+		if (mdev->tconn->current_tle_writes >= p)
+			start_new_tl_epoch(mdev->tconn);
 
 		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);
+	case QUEUE_FOR_SEND_OOS:
+		mod_rq_state(req, m, 0, RQ_NET_QUEUED);
+		req->w.cb =  w_send_out_of_sync;
+		drbd_queue_work(&mdev->tconn->sender_work, &req->w);
 		break;
 
-	case read_retry_remote_canceled:
-	case send_canceled:
-	case send_failed:
+	case READ_RETRY_REMOTE_CANCELED:
+	case SEND_CANCELED:
+	case SEND_FAILED:
 		/* real cleanup will be done from tl_clear.  just update flags
 		 * so it is no longer marked as on the worker queue */
-		req->rq_state &= ~RQ_NET_QUEUED;
-		/* if we did it right, tl_clear should be scheduled only after
-		 * this, so this should not be necessary! */
-		_req_may_be_done_not_susp(req, m);
+		mod_rq_state(req, m, RQ_NET_QUEUED, 0);
 		break;
 
-	case handed_over_to_network:
+	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) {
+		    !(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK))) {
 			/* this is what is dangerous about protocol A:
 			 * pretend it was successfully written on the peer. */
-			if (req->rq_state & RQ_NET_PENDING) {
-				dec_ap_pending(mdev);
-				req->rq_state &= ~RQ_NET_PENDING;
-				req->rq_state |= RQ_NET_OK;
-			} /* else: neg-ack was faster... */
+			if (req->rq_state & RQ_NET_PENDING)
+				mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
+			/* else: neg-ack was faster... */
 			/* it is still not yet RQ_NET_DONE until the
 			 * corresponding epoch barrier got acked as well,
 			 * so we know what to dirty on connection loss */
 		}
-		req->rq_state &= ~RQ_NET_QUEUED;
-		req->rq_state |= RQ_NET_SENT;
-		_req_may_be_done_not_susp(req, m);
+		mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
 		break;
 
-	case oos_handed_to_network:
+	case OOS_HANDED_TO_NETWORK:
 		/* Was not set PENDING, no longer QUEUED, so is now DONE
 		 * as far as this connection is concerned. */
-		req->rq_state &= ~RQ_NET_QUEUED;
-		req->rq_state |= RQ_NET_DONE;
-		_req_may_be_done_not_susp(req, m);
+		mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_DONE);
 		break;
 
-	case connection_lost_while_pending:
+	case CONNECTION_LOST_WHILE_PENDING:
 		/* transfer log cleanup after connection loss */
-		/* assert something? */
-		if (req->rq_state & RQ_NET_PENDING)
-			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))
-			_req_may_be_done(req, m); /* Allowed while state.susp */
+		mod_rq_state(req, m,
+				RQ_NET_OK|RQ_NET_PENDING|RQ_COMPLETION_SUSP,
+				RQ_NET_DONE);
 		break;
 
-	case conflict_discarded_by_peer:
-		/* for discarded conflicting writes of multiple primaries,
+	case CONFLICT_RESOLVED:
+		/* for superseded conflicting writes of multiple primaries,
 		 * there is no need to keep anything in the tl, potential
-		 * node crashes are covered by the activity log. */
-		if (what == conflict_discarded_by_peer)
-			dev_alert(DEV, "Got DiscardAck packet %llus +%u!"
-			      " DRBD is not a random data generator!\n",
-			      (unsigned long long)req->sector, req->size);
-		req->rq_state |= RQ_NET_DONE;
-		/* fall through */
-	case write_acked_by_peer_and_sis:
-	case write_acked_by_peer:
-		if (what == write_acked_by_peer_and_sis)
-			req->rq_state |= RQ_NET_SIS;
+		 * node crashes are covered by the activity log.
+		 *
+		 * If this request had been marked as RQ_POSTPONED before,
+		 * it will actually not be completed, but "restarted",
+		 * resubmitted from the retry worker context. */
+		D_ASSERT(req->rq_state & RQ_NET_PENDING);
+		D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
+		mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_DONE|RQ_NET_OK);
+		break;
+
+	case WRITE_ACKED_BY_PEER_AND_SIS:
+		req->rq_state |= RQ_NET_SIS;
+	case WRITE_ACKED_BY_PEER:
+		D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
 		/* protocol C; successfully written on peer.
 		 * Nothing more to do here.
 		 * We want to keep the tl in place for all protocols, to cater
 		 * for volatile write-back caches on lower level devices. */
 
-	case recv_acked_by_peer:
+		goto ack_common;
+	case RECV_ACKED_BY_PEER:
+		D_ASSERT(req->rq_state & RQ_EXP_RECEIVE_ACK);
 		/* protocol B; pretends to be successfully written on peer.
-		 * see also notes above in handed_over_to_network about
+		 * see also notes above in HANDED_OVER_TO_NETWORK about
 		 * protocol != C */
-		req->rq_state |= RQ_NET_OK;
+	ack_common:
 		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);
+		mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
 		break;
 
-	case neg_acked:
-		/* assert something? */
-		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);
+	case POSTPONE_WRITE:
+		D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
+		/* If this node has already detected the write conflict, the
+		 * worker will be waiting on misc_wait.  Wake it up once this
+		 * request has completed locally.
+		 */
+		D_ASSERT(req->rq_state & RQ_NET_PENDING);
+		req->rq_state |= RQ_POSTPONED;
+		if (req->i.waiting)
+			wake_up(&mdev->misc_wait);
+		/* Do not clear RQ_NET_PENDING. This request will make further
+		 * progress via restart_conflicting_writes() or
+		 * fail_postponed_requests(). Hopefully. */
+		break;
 
-		req->rq_state |= RQ_NET_DONE;
-		_req_may_be_done_not_susp(req, m);
-		/* else: done by handed_over_to_network */
+	case NEG_ACKED:
+		mod_rq_state(req, m, RQ_NET_OK|RQ_NET_PENDING, 0);
 		break;
 
-	case fail_frozen_disk_io:
+	case FAIL_FROZEN_DISK_IO:
 		if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 			break;
-
-		_req_may_be_done(req, m); /* Allowed while state.susp */
+		mod_rq_state(req, m, RQ_COMPLETION_SUSP, 0);
 		break;
 
-	case restart_frozen_disk_io:
+	case RESTART_FROZEN_DISK_IO:
 		if (!(req->rq_state & RQ_LOCAL_COMPLETED))
 			break;
 
-		req->rq_state &= ~RQ_LOCAL_COMPLETED;
+		mod_rq_state(req, m,
+				RQ_COMPLETION_SUSP|RQ_LOCAL_COMPLETED,
+				RQ_LOCAL_PENDING);
 
 		rv = MR_READ;
 		if (bio_data_dir(req->master_bio) == WRITE)
 			rv = MR_WRITE;
 
-		get_ldev(mdev);
+		get_ldev(mdev); /* always succeeds in this call path */
 		req->w.cb = w_restart_disk_io;
-		drbd_queue_work(&mdev->data.work, &req->w);
+		drbd_queue_work(&mdev->tconn->sender_work, &req->w);
 		break;
 
-	case resend:
+	case RESEND:
 		/* Simply complete (local only) READs. */
 		if (!(req->rq_state & RQ_WRITE) && !req->w.cb) {
-			_req_may_be_done(req, m);
+			mod_rq_state(req, m, RQ_COMPLETION_SUSP, 0);
 			break;
 		}
 
 		/* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
-		   before the connection loss (B&C only); only P_BARRIER_ACK was missing.
-		   Trowing them out of the TL here by pretending we got a BARRIER_ACK
-		   We ensure that the peer was not rebooted */
+		   before the connection loss (B&C only); only P_BARRIER_ACK
+		   (or the local completion?) was missing when we suspended.
+		   Throwing them out of the TL here by pretending we got a BARRIER_ACK.
+		   During connection handshake, we ensure that the peer was not rebooted. */
 		if (!(req->rq_state & RQ_NET_OK)) {
+			/* FIXME could this possibly be a req->w.cb == w_send_out_of_sync?
+			 * in that case we must not set RQ_NET_PENDING. */
+
+			mod_rq_state(req, m, RQ_COMPLETION_SUSP, RQ_NET_QUEUED|RQ_NET_PENDING);
 			if (req->w.cb) {
-				drbd_queue_work(&mdev->data.work, &req->w);
+				drbd_queue_work(&mdev->tconn->sender_work, &req->w);
 				rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
-			}
+			} /* else: FIXME can this happen? */
 			break;
 		}
-		/* else, fall through to barrier_acked */
+		/* else, fall through to BARRIER_ACKED */
 
-	case barrier_acked:
+	case BARRIER_ACKED:
+		/* barrier ack for READ requests does not make sense */
 		if (!(req->rq_state & RQ_WRITE))
 			break;
 
 		if (req->rq_state & RQ_NET_PENDING) {
-			/* barrier came in before all requests have been acked.
+			/* barrier came in before all requests were acked.
 			 * this is bad, because if the connection is lost now,
 			 * we won't be able to clean them up... */
-			dev_err(DEV, "FIXME (barrier_acked but pending)\n");
-			list_move(&req->tl_requests, &mdev->out_of_sequence_requests);
+			dev_err(DEV, "FIXME (BARRIER_ACKED but pending)\n");
 		}
-		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 */
+		/* Allowed to complete requests, even while suspended.
+		 * As this is called for all requests within a matching epoch,
+		 * we need to filter, and only set RQ_NET_DONE for those that
+		 * have actually been on the wire. */
+		mod_rq_state(req, m, RQ_COMPLETION_SUSP,
+				(req->rq_state & RQ_NET_MASK) ? RQ_NET_DONE : 0);
 		break;
 
-	case data_received:
+	case DATA_RECEIVED:
 		D_ASSERT(req->rq_state & RQ_NET_PENDING);
-		dec_ap_pending(mdev);
-		req->rq_state &= ~RQ_NET_PENDING;
-		req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
-		_req_may_be_done_not_susp(req, m);
+		mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK|RQ_NET_DONE);
 		break;
 	};
 
@@ -768,75 +767,265 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
  *   since size may be bigger than BM_BLOCK_SIZE,
  *   we may need to check several bits.
  */
-static int drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
+static bool drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
 {
 	unsigned long sbnr, ebnr;
 	sector_t esector, nr_sectors;
 
 	if (mdev->state.disk == D_UP_TO_DATE)
-		return 1;
-	if (mdev->state.disk >= D_OUTDATED)
-		return 0;
-	if (mdev->state.disk <  D_INCONSISTENT)
-		return 0;
-	/* state.disk == D_INCONSISTENT   We will have a look at the BitMap */
-	nr_sectors = drbd_get_capacity(mdev->this_bdev);
+		return true;
+	if (mdev->state.disk != D_INCONSISTENT)
+		return false;
 	esector = sector + (size >> 9) - 1;
-
+	nr_sectors = drbd_get_capacity(mdev->this_bdev);
 	D_ASSERT(sector  < nr_sectors);
 	D_ASSERT(esector < nr_sectors);
 
 	sbnr = BM_SECT_TO_BIT(sector);
 	ebnr = BM_SECT_TO_BIT(esector);
 
-	return 0 == drbd_bm_count_bits(mdev, sbnr, ebnr);
+	return drbd_bm_count_bits(mdev, sbnr, ebnr) == 0;
+}
+
+static bool remote_due_to_read_balancing(struct drbd_conf *mdev, sector_t sector,
+		enum drbd_read_balancing rbm)
+{
+	struct backing_dev_info *bdi;
+	int stripe_shift;
+
+	switch (rbm) {
+	case RB_CONGESTED_REMOTE:
+		bdi = &mdev->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
+		return bdi_read_congested(bdi);
+	case RB_LEAST_PENDING:
+		return atomic_read(&mdev->local_cnt) >
+			atomic_read(&mdev->ap_pending_cnt) + atomic_read(&mdev->rs_pending_cnt);
+	case RB_32K_STRIPING:  /* stripe_shift = 15 */
+	case RB_64K_STRIPING:
+	case RB_128K_STRIPING:
+	case RB_256K_STRIPING:
+	case RB_512K_STRIPING:
+	case RB_1M_STRIPING:   /* stripe_shift = 20 */
+		stripe_shift = (rbm - RB_32K_STRIPING + 15);
+		return (sector >> (stripe_shift - 9)) & 1;
+	case RB_ROUND_ROBIN:
+		return test_and_change_bit(READ_BALANCE_RR, &mdev->flags);
+	case RB_PREFER_REMOTE:
+		return true;
+	case RB_PREFER_LOCAL:
+	default:
+		return false;
+	}
+}
+
+/*
+ * complete_conflicting_writes  -  wait for any conflicting write requests
+ *
+ * The write_requests tree contains all active write requests which we
+ * currently know about.  Wait for any requests to complete which conflict with
+ * the new one.
+ *
+ * Only way out: remove the conflicting intervals from the tree.
+ */
+static void complete_conflicting_writes(struct drbd_request *req)
+{
+	DEFINE_WAIT(wait);
+	struct drbd_conf *mdev = req->w.mdev;
+	struct drbd_interval *i;
+	sector_t sector = req->i.sector;
+	int size = req->i.size;
+
+	i = drbd_find_overlap(&mdev->write_requests, sector, size);
+	if (!i)
+		return;
+
+	for (;;) {
+		prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
+		i = drbd_find_overlap(&mdev->write_requests, sector, size);
+		if (!i)
+			break;
+		/* Indicate to wake up device->misc_wait on progress.  */
+		i->waiting = true;
+		spin_unlock_irq(&mdev->tconn->req_lock);
+		schedule();
+		spin_lock_irq(&mdev->tconn->req_lock);
+	}
+	finish_wait(&mdev->misc_wait, &wait);
 }
 
+/* called within req_lock and rcu_read_lock() */
 static void maybe_pull_ahead(struct drbd_conf *mdev)
 {
-	int congested = 0;
+	struct drbd_tconn *tconn = mdev->tconn;
+	struct net_conf *nc;
+	bool congested = false;
+	enum drbd_on_congestion on_congestion;
+
+	nc = rcu_dereference(tconn->net_conf);
+	on_congestion = nc ? nc->on_congestion : OC_BLOCK;
+	if (on_congestion == OC_BLOCK ||
+	    tconn->agreed_pro_version < 96)
+		return;
 
 	/* If I don't even have good local storage, we can not reasonably try
 	 * to pull ahead of the peer. We also need the local reference to make
 	 * sure mdev->act_log is there.
-	 * Note: caller has to make sure that net_conf is there.
 	 */
 	if (!get_ldev_if_state(mdev, D_UP_TO_DATE))
 		return;
 
-	if (mdev->net_conf->cong_fill &&
-	    atomic_read(&mdev->ap_in_flight) >= mdev->net_conf->cong_fill) {
+	if (nc->cong_fill &&
+	    atomic_read(&mdev->ap_in_flight) >= nc->cong_fill) {
 		dev_info(DEV, "Congestion-fill threshold reached\n");
-		congested = 1;
+		congested = true;
 	}
 
-	if (mdev->act_log->used >= mdev->net_conf->cong_extents) {
+	if (mdev->act_log->used >= nc->cong_extents) {
 		dev_info(DEV, "Congestion-extents threshold reached\n");
-		congested = 1;
+		congested = true;
 	}
 
 	if (congested) {
-		queue_barrier(mdev); /* last barrier, after mirrored writes */
+		/* start a new epoch for non-mirrored writes */
+		start_new_tl_epoch(mdev->tconn);
 
-		if (mdev->net_conf->on_congestion == OC_PULL_AHEAD)
+		if (on_congestion == OC_PULL_AHEAD)
 			_drbd_set_state(_NS(mdev, conn, C_AHEAD), 0, NULL);
-		else  /*mdev->net_conf->on_congestion == OC_DISCONNECT */
+		else  /*nc->on_congestion == OC_DISCONNECT */
 			_drbd_set_state(_NS(mdev, conn, C_DISCONNECTING), 0, NULL);
 	}
 	put_ldev(mdev);
 }
 
-static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, unsigned long start_time)
+/* If this returns false, and req->private_bio is still set,
+ * this should be submitted locally.
+ *
+ * If it returns false, but req->private_bio is not set,
+ * we do not have access to good data :(
+ *
+ * Otherwise, this destroys req->private_bio, if any,
+ * and returns true.
+ */
+static bool do_remote_read(struct drbd_request *req)
+{
+	struct drbd_conf *mdev = req->w.mdev;
+	enum drbd_read_balancing rbm;
+
+	if (req->private_bio) {
+		if (!drbd_may_do_local_read(mdev,
+					req->i.sector, req->i.size)) {
+			bio_put(req->private_bio);
+			req->private_bio = NULL;
+			put_ldev(mdev);
+		}
+	}
+
+	if (mdev->state.pdsk != D_UP_TO_DATE)
+		return false;
+
+	if (req->private_bio == NULL)
+		return true;
+
+	/* TODO: improve read balancing decisions, take into account drbd
+	 * protocol, pending requests etc. */
+
+	rcu_read_lock();
+	rbm = rcu_dereference(mdev->ldev->disk_conf)->read_balancing;
+	rcu_read_unlock();
+
+	if (rbm == RB_PREFER_LOCAL && req->private_bio)
+		return false; /* submit locally */
+
+	if (remote_due_to_read_balancing(mdev, req->i.sector, rbm)) {
+		if (req->private_bio) {
+			bio_put(req->private_bio);
+			req->private_bio = NULL;
+			put_ldev(mdev);
+		}
+		return true;
+	}
+
+	return false;
+}
+
+/* returns number of connections (== 1, for drbd 8.4)
+ * expected to actually write this data,
+ * which does NOT include those that we are L_AHEAD for. */
+static int drbd_process_write_request(struct drbd_request *req)
+{
+	struct drbd_conf *mdev = req->w.mdev;
+	int remote, send_oos;
+
+	rcu_read_lock();
+	remote = drbd_should_do_remote(mdev->state);
+	if (remote) {
+		maybe_pull_ahead(mdev);
+		remote = drbd_should_do_remote(mdev->state);
+	}
+	send_oos = drbd_should_send_out_of_sync(mdev->state);
+	rcu_read_unlock();
+
+	/* Need to replicate writes.  Unless it is an empty flush,
+	 * which is better mapped to a DRBD P_BARRIER packet,
+	 * also for drbd wire protocol compatibility reasons.
+	 * If this was a flush, just start a new epoch.
+	 * Unless the current epoch was empty anyways, or we are not currently
+	 * replicating, in which case there is no point. */
+	if (unlikely(req->i.size == 0)) {
+		/* The only size==0 bios we expect are empty flushes. */
+		D_ASSERT(req->master_bio->bi_rw & REQ_FLUSH);
+		if (remote)
+			start_new_tl_epoch(mdev->tconn);
+		return 0;
+	}
+
+	if (!remote && !send_oos)
+		return 0;
+
+	D_ASSERT(!(remote && send_oos));
+
+	if (remote) {
+		_req_mod(req, TO_BE_SENT);
+		_req_mod(req, QUEUE_FOR_NET_WRITE);
+	} else if (drbd_set_out_of_sync(mdev, req->i.sector, req->i.size))
+		_req_mod(req, QUEUE_FOR_SEND_OOS);
+
+	return remote;
+}
+
+static void
+drbd_submit_req_private_bio(struct drbd_request *req)
+{
+	struct drbd_conf *mdev = req->w.mdev;
+	struct bio *bio = req->private_bio;
+	const int rw = bio_rw(bio);
+
+	bio->bi_bdev = mdev->ldev->backing_bdev;
+
+	/* State may have changed since we grabbed our reference on the
+	 * ->ldev member. Double check, and short-circuit to endio.
+	 * In case the last activity log transaction failed to get on
+	 * stable storage, and this is a WRITE, we may not even submit
+	 * this bio. */
+	if (get_ldev(mdev)) {
+		if (drbd_insert_fault(mdev,
+				      rw == WRITE ? DRBD_FAULT_DT_WR
+				    : rw == READ  ? DRBD_FAULT_DT_RD
+				    :               DRBD_FAULT_DT_RA))
+			bio_endio(bio, -EIO);
+		else
+			generic_make_request(bio);
+		put_ldev(mdev);
+	} else
+		bio_endio(bio, -EIO);
+}
+
+void __drbd_make_request(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 bio_and_error m = { NULL, };
 	struct drbd_request *req;
-	int local, remote, send_oos = 0;
-	int err = -EIO;
-	int ret = 0;
-	union drbd_state s;
+	bool no_remote = false;
 
 	/* allocate outside of all locks; */
 	req = drbd_req_new(mdev, bio);
@@ -846,55 +1035,14 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, uns
 		 * if user cannot handle io errors, that's not our business. */
 		dev_err(DEV, "could not kmalloc() req\n");
 		bio_endio(bio, -ENOMEM);
-		return 0;
+		return;
 	}
 	req->start_time = start_time;
 
-	local = get_ldev(mdev);
-	if (!local) {
-		bio_put(req->private_bio); /* or we get a bio leak */
+	if (!get_ldev(mdev)) {
+		bio_put(req->private_bio);
 		req->private_bio = NULL;
 	}
-	if (rw == WRITE) {
-		/* Need to replicate writes.  Unless it is an empty flush,
-		 * which is better mapped to a DRBD P_BARRIER packet,
-		 * also for drbd wire protocol compatibility reasons. */
-		if (unlikely(size == 0)) {
-			/* The only size==0 bios we expect are empty flushes. */
-			D_ASSERT(bio->bi_rw & REQ_FLUSH);
-			remote = 0;
-		} else
-			remote = 1;
-	} else {
-		/* READ || READA */
-		if (local) {
-			if (!drbd_may_do_local_read(mdev, sector, size)) {
-				/* we could kick the syncer to
-				 * sync this extent asap, wait for
-				 * it, then continue locally.
-				 * Or just issue the request remotely.
-				 */
-				local = 0;
-				bio_put(req->private_bio);
-				req->private_bio = NULL;
-				put_ldev(mdev);
-			}
-		}
-		remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
-	}
-
-	/* If we have a disk, but a READA request is mapped to remote,
-	 * we are R_PRIMARY, D_INCONSISTENT, SyncTarget.
-	 * Just fail that READA request right here.
-	 *
-	 * THINK: maybe fail all READA when not local?
-	 *        or make this configurable...
-	 *        if network is slow, READA won't do any good.
-	 */
-	if (rw == READA && mdev->state.disk >= D_INCONSISTENT && !local) {
-		err = -EWOULDBLOCK;
-		goto fail_and_free_req;
-	}
 
 	/* For WRITES going to the local disk, grab a reference on the target
 	 * extent.  This waits for any resync activity in the corresponding
@@ -903,349 +1051,131 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio, uns
 	 * of transactional on-disk meta data updates.
 	 * Empty flushes don't need to go into the activity log, they can only
 	 * flush data for pending writes which are already in there. */
-	if (rw == WRITE && local && size
-	&& !drbd_test_flag(mdev, AL_SUSPENDED)) {
+	if (rw == WRITE && req->private_bio && req->i.size
+	&& !test_bit(AL_SUSPENDED, &mdev->flags)) {
 		req->rq_state |= RQ_IN_ACT_LOG;
-		drbd_al_begin_io(mdev, sector);
+		drbd_al_begin_io(mdev, &req->i);
 	}
 
-	s = mdev->state;
-	remote = remote && drbd_should_do_remote(s);
-	send_oos = rw == WRITE && drbd_should_send_oos(s);
-	D_ASSERT(!(remote && send_oos));
-
-	if (!(local || remote) && !is_susp(mdev->state)) {
-		if (__ratelimit(&drbd_ratelimit_state))
-			dev_err(DEV, "IO ERROR: neither local nor remote data, sector %llu+%u\n",
-					(unsigned long long)req->sector, req->size >> 9);
-		goto fail_free_complete;
-	}
-
-	/* For WRITE request, we have to make sure that we have an
-	 * unused_spare_tle, in case we need to start a new epoch.
-	 * I try to be smart and avoid to pre-allocate always "just in case",
-	 * 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 || send_oos) &&
-	    mdev->unused_spare_tle == NULL &&
-	    drbd_test_flag(mdev, CREATE_BARRIER)) {
-allocate_barrier:
-		b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_NOIO);
-		if (!b) {
-			dev_err(DEV, "Failed to alloc barrier.\n");
-			err = -ENOMEM;
-			goto fail_free_complete;
-		}
+	spin_lock_irq(&mdev->tconn->req_lock);
+	if (rw == WRITE) {
+		/* This may temporarily give up the req_lock,
+		 * but will re-aquire it before it returns here.
+		 * Needs to be before the check on drbd_suspended() */
+		complete_conflicting_writes(req);
 	}
 
-	/* GOOD, everything prepared, grab the spin_lock */
-	spin_lock_irq(&mdev->req_lock);
-
-	if (is_susp(mdev->state)) {
-		/* If we got suspended, use the retry mechanism of
-		   drbd_make_request() to restart processing of this
-		   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;
-	}
+	/* no more giving up req_lock from now on! */
 
-	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");
-			spin_unlock_irq(&mdev->req_lock);
-			goto fail_free_complete;
+	if (drbd_suspended(mdev)) {
+		/* push back and retry: */
+		req->rq_state |= RQ_POSTPONED;
+		if (req->private_bio) {
+			bio_put(req->private_bio);
+			req->private_bio = NULL;
+			put_ldev(mdev);
 		}
+		goto out;
 	}
 
-	if (b && mdev->unused_spare_tle == NULL) {
-		mdev->unused_spare_tle = b;
-		b = NULL;
-	}
-	if (rw == WRITE && (remote || send_oos) &&
-	    mdev->unused_spare_tle == NULL &&
-	    drbd_test_flag(mdev, CREATE_BARRIER)) {
-		/* someone closed the current epoch
-		 * while we were grabbing the spinlock */
-		spin_unlock_irq(&mdev->req_lock);
-		goto allocate_barrier;
-	}
-
-
 	/* Update disk stats */
 	_drbd_start_io_acct(mdev, req, bio);
 
-	/* _maybe_start_new_epoch(mdev);
-	 * If we need to generate a write barrier packet, we have to add the
-	 * new epoch (barrier) object, and queue the barrier packet for sending,
-	 * and queue the req's data after it _within the same lock_, otherwise
-	 * we have race conditions were the reorder domains could be mixed up.
-	 *
-	 * Even read requests may start a new epoch and queue the corresponding
-	 * 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 || send_oos) && mdev->unused_spare_tle &&
-	    drbd_test_and_clear_flag(mdev, CREATE_BARRIER)) {
-		_tl_add_barrier(mdev, mdev->unused_spare_tle);
-		mdev->unused_spare_tle = NULL;
-	} else {
-		D_ASSERT(!(remote && rw == WRITE &&
-			   drbd_test_flag(mdev, CREATE_BARRIER)));
+	/* We fail READ/READA early, if we can not serve it.
+	 * We must do this before req is registered on any lists.
+	 * Otherwise, drbd_req_complete() will queue failed READ for retry. */
+	if (rw != WRITE) {
+		if (!do_remote_read(req) && !req->private_bio)
+			goto nodata;
 	}
 
-	/* NOTE
-	 * Actually, 'local' may be wrong here already, since we may have failed
-	 * to write to the meta data, and may become wrong anytime because of
-	 * local io-error for some other request, which would lead to us
-	 * "detaching" the local disk.
-	 *
-	 * 'remote' may become wrong any time because the network could fail.
-	 *
-	 * This is a harmless race condition, though, since it is handled
-	 * correctly at the appropriate places; so it just defers the failure
-	 * of the respective operation.
-	 */
-
-	/* mark them early for readability.
-	 * this just sets some state flags. */
-	if (remote)
-		_req_mod(req, to_be_send);
-	if (local)
-		_req_mod(req, to_be_submitted);
-
-	/* check this request on the collision detection hash tables.
-	 * if we have a conflict, just complete it here.
-	 * THINK do we want to check reads, too? (I don't think so...) */
-	if (rw == WRITE && _req_conflicts(req))
-		goto fail_conflicting;
+	/* which transfer log epoch does this belong to? */
+	req->epoch = atomic_read(&mdev->tconn->current_tle_nr);
 
 	/* no point in adding empty flushes to the transfer log,
 	 * they are mapped to drbd barriers already. */
-	if (likely(size!=0))
-		list_add_tail(&req->tl_requests, &mdev->newest_tle->requests);
+	if (likely(req->i.size!=0)) {
+		if (rw == WRITE)
+			mdev->tconn->current_tle_writes++;
 
-	/* NOTE remote first: to get the concurrent write detection right,
-	 * we must register the request before start of local IO.  */
-	if (remote) {
-		/* either WRITE and C_CONNECTED,
-		 * or READ, and no local disk,
-		 * or READ, but not in sync.
-		 */
-		_req_mod(req, (rw == WRITE)
-				? queue_for_net_write
-				: queue_for_net_read);
+		list_add_tail(&req->tl_requests, &mdev->tconn->transfer_log);
 	}
-	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)
-		maybe_pull_ahead(mdev);
 
-	/* If this was a flush, queue a drbd barrier/start a new epoch.
-	 * Unless the current epoch was empty anyways, or we are not currently
-	 * replicating, in which case there is no point. */
-	if (unlikely(bio->bi_rw & REQ_FLUSH)
-		&& mdev->newest_tle->n_writes
-		&& drbd_should_do_remote(mdev->state))
-		queue_barrier(mdev);
-
-	spin_unlock_irq(&mdev->req_lock);
-	kfree(b); /* if someone else has beaten us to it... */
-
-	if (local) {
-		req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
-
-		/* State may have changed since we grabbed our reference on the
-		 * mdev->ldev member. Double check, and short-circuit to endio.
-		 * In case the last activity log transaction failed to get on
-		 * stable storage, and this is a WRITE, we may not even submit
-		 * this bio. */
-		if (get_ldev(mdev)) {
-			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);
-			put_ldev(mdev);
+	if (rw == WRITE) {
+		if (!drbd_process_write_request(req))
+			no_remote = true;
+	} else {
+		/* We either have a private_bio, or we can read from remote.
+		 * Otherwise we had done the goto nodata above. */
+		if (req->private_bio == NULL) {
+			_req_mod(req, TO_BE_SENT);
+			_req_mod(req, QUEUE_FOR_NET_READ);
 		} else
-			bio_endio(req->private_bio, -EIO);
+			no_remote = true;
 	}
 
-	return 0;
-
-fail_conflicting:
-	/* this is a conflicting request.
-	 * even though it may have been only _partially_
-	 * overlapping with one of the currently pending requests,
-	 * without even submitting or sending it, we will
-	 * pretend that it was successfully served right now.
-	 */
-	_drbd_end_io_acct(mdev, req);
-	spin_unlock_irq(&mdev->req_lock);
-	if (remote)
-		dec_ap_pending(mdev);
-	/* THINK: do we want to fail it (-EIO), or pretend success?
-	 * this pretends success. */
-	err = 0;
-
-fail_free_complete:
-	if (req->rq_state & RQ_IN_ACT_LOG)
-		drbd_al_complete_io(mdev, sector);
-fail_and_free_req:
-	if (local) {
-		bio_put(req->private_bio);
-		req->private_bio = NULL;
-		put_ldev(mdev);
+	if (req->private_bio) {
+		/* needs to be marked within the same spinlock */
+		_req_mod(req, TO_BE_SUBMITTED);
+		/* but we need to give up the spinlock to submit */
+		spin_unlock_irq(&mdev->tconn->req_lock);
+		drbd_submit_req_private_bio(req);
+		spin_lock_irq(&mdev->tconn->req_lock);
+	} else if (no_remote) {
+nodata:
+		if (__ratelimit(&drbd_ratelimit_state))
+			dev_err(DEV, "IO ERROR: neither local nor remote data, sector %llu+%u\n",
+					(unsigned long long)req->i.sector, req->i.size >> 9);
+		/* A write may have been queued for send_oos, however.
+		 * So we can not simply free it, we must go through drbd_req_put_completion_ref() */
 	}
-	if (!ret)
-		bio_endio(bio, err);
-
-	drbd_req_free(req);
-	dec_ap_bio(mdev);
-	kfree(b);
-
-	return ret;
-}
 
-/* helper function for drbd_make_request
- * if we can determine just by the mdev (state) that this request will fail,
- * return 1
- * otherwise return 0
- */
-static int drbd_fail_request_early(struct drbd_conf *mdev, int is_write)
-{
-	if (mdev->state.role != R_PRIMARY &&
-		(!allow_oos || is_write)) {
-		if (__ratelimit(&drbd_ratelimit_state)) {
-			dev_err(DEV, "Process %s[%u] tried to %s; "
-			    "since we are not in Primary state, "
-			    "we cannot allow this\n",
-			    current->comm, current->pid,
-			    is_write ? "WRITE" : "READ");
-		}
-		return 1;
-	}
+out:
+	if (drbd_req_put_completion_ref(req, &m, 1))
+		kref_put(&req->kref, drbd_req_destroy);
+	spin_unlock_irq(&mdev->tconn->req_lock);
 
-	return 0;
+	if (m.bio)
+		complete_master_bio(mdev, &m);
+	return;
 }
 
 void 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;
-	}
-
 	start_time = jiffies;
 
 	/*
 	 * what we "blindly" assume:
 	 */
-	D_ASSERT((bio->bi_size & 0x1ff) == 0);
-
-	/* to make some things easier, force alignment of requests within the
-	 * granularity of our hash tables */
-	s_enr = bio->bi_sector >> HT_SHIFT;
-	e_enr = bio->bi_size ? (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT : s_enr;
-
-	if (likely(s_enr == e_enr)) {
-		do {
-			inc_ap_bio(mdev, 1);
-		} while (drbd_make_request_common(mdev, bio, start_time));
-		return;
-	}
-
-	/* 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_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",
-		    bio->bi_vcnt, bio->bi_idx, bio->bi_size,
-		    (unsigned long long)bio->bi_sector);
-		bio_endio(bio, -EINVAL);
-	} else {
-		/* This bio crosses some boundary, so we have to split it. */
-		struct bio_pair *bp;
-		/* works for the "do not cross hash slot boundaries" case
-		 * e.g. sector 262269, size 4096
-		 * s_enr = 262269 >> 6 = 4097
-		 * e_enr = (262269+8-1) >> 6 = 4098
-		 * HT_SHIFT = 6
-		 * sps = 64, mask = 63
-		 * first_sectors = 64 - (262269 & 63) = 3
-		 */
-		const sector_t sect = bio->bi_sector;
-		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, first_sectors);
+	D_ASSERT(IS_ALIGNED(bio->bi_size, 512));
 
-		/* we need to get a "reference count" (ap_bio_cnt)
-		 * to avoid races with the disconnect/reconnect/suspend code.
-		 * In case we need to split the bio here, we need to get three references
-		 * atomically, otherwise we might deadlock when trying to submit the
-		 * second one! */
-		inc_ap_bio(mdev, 3);
-
-		D_ASSERT(e_enr == s_enr + 1);
-
-		while (drbd_make_request_common(mdev, &bp->bio1, start_time))
-			inc_ap_bio(mdev, 1);
-
-		while (drbd_make_request_common(mdev, &bp->bio2, start_time))
-			inc_ap_bio(mdev, 1);
-
-		dec_ap_bio(mdev);
-
-		bio_pair_release(bp);
-	}
+	inc_ap_bio(mdev);
+	__drbd_make_request(mdev, bio, start_time);
 }
 
-/* This is called by bio_add_page().  With this function we reduce
- * the number of BIOs that span over multiple DRBD_MAX_BIO_SIZEs
- * units (was AL_EXTENTs).
+/* This is called by bio_add_page().
+ *
+ * q->max_hw_sectors and other global limits are already enforced there.
  *
- * we do the calculation within the lower 32bit of the byte offsets,
- * since we don't care for actual offset, but only check whether it
- * would cross "activity log extent" boundaries.
+ * We need to call down to our lower level device,
+ * in case it has special restrictions.
+ *
+ * We also may need to enforce configured max-bio-bvecs limits.
  *
  * 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.
+ * regardless of size and offset, so no need to ask lower levels.
  */
 int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
 {
 	struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
-	unsigned int bio_offset =
-		(unsigned int)bvm->bi_sector << 9; /* 32 bit */
 	unsigned int bio_size = bvm->bi_size;
-	int limit, backing_limit;
-
-	limit = DRBD_MAX_BIO_SIZE
-	      - ((bio_offset & (DRBD_MAX_BIO_SIZE-1)) + bio_size);
-	if (limit < 0)
-		limit = 0;
-	if (bio_size == 0) {
-		if (limit <= bvec->bv_len)
-			limit = bvec->bv_len;
-	} else if (limit && get_ldev(mdev)) {
+	int limit = DRBD_MAX_BIO_SIZE;
+	int backing_limit;
+
+	if (bio_size && get_ldev(mdev)) {
 		struct request_queue * const b =
 			mdev->ldev->backing_bdev->bd_disk->queue;
 		if (b->merge_bvec_fn) {
@@ -1257,24 +1187,38 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
 	return limit;
 }
 
+struct drbd_request *find_oldest_request(struct drbd_tconn *tconn)
+{
+	/* Walk the transfer log,
+	 * and find the oldest not yet completed request */
+	struct drbd_request *r;
+	list_for_each_entry(r, &tconn->transfer_log, tl_requests) {
+		if (atomic_read(&r->completion_ref))
+			return r;
+	}
+	return NULL;
+}
+
 void request_timer_fn(unsigned long data)
 {
 	struct drbd_conf *mdev = (struct drbd_conf *) data;
+	struct drbd_tconn *tconn = mdev->tconn;
 	struct drbd_request *req; /* oldest request */
-	struct list_head *le;
+	struct net_conf *nc;
 	unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
 	unsigned long now;
 
-	if (get_net_conf(mdev)) {
-		if (mdev->state.conn >= C_WF_REPORT_PARAMS)
-			ent = mdev->net_conf->timeout*HZ/10
-				* mdev->net_conf->ko_count;
-		put_net_conf(mdev);
-	}
+	rcu_read_lock();
+	nc = rcu_dereference(tconn->net_conf);
+	if (nc && mdev->state.conn >= C_WF_REPORT_PARAMS)
+		ent = nc->timeout * HZ/10 * nc->ko_count;
+
 	if (get_ldev(mdev)) { /* implicit state.disk >= D_INCONSISTENT */
-		dt = mdev->ldev->dc.disk_timeout * HZ / 10;
+		dt = rcu_dereference(mdev->ldev->disk_conf)->disk_timeout * HZ / 10;
 		put_ldev(mdev);
 	}
+	rcu_read_unlock();
+
 	et = min_not_zero(dt, ent);
 
 	if (!et)
@@ -1282,17 +1226,14 @@ void request_timer_fn(unsigned long data)
 
 	now = jiffies;
 
-	spin_lock_irq(&mdev->req_lock);
-	le = &mdev->oldest_tle->requests;
-	if (list_empty(le)) {
-		spin_unlock_irq(&mdev->req_lock);
+	spin_lock_irq(&tconn->req_lock);
+	req = find_oldest_request(tconn);
+	if (!req) {
+		spin_unlock_irq(&tconn->req_lock);
 		mod_timer(&mdev->request_timer, now + et);
 		return;
 	}
 
-	le = le->prev;
-	req = list_entry(le, struct drbd_request, tl_requests);
-
 	/* The request is considered timed out, if
 	 * - we have some effective timeout from the configuration,
 	 *   with above state restrictions applied,
@@ -1311,17 +1252,17 @@ void request_timer_fn(unsigned long data)
 	 */
 	if (ent && req->rq_state & RQ_NET_PENDING &&
 		 time_after(now, req->start_time + ent) &&
-		!time_in_range(now, mdev->last_reconnect_jif, mdev->last_reconnect_jif + ent)) {
+		!time_in_range(now, tconn->last_reconnect_jif, tconn->last_reconnect_jif + ent)) {
 		dev_warn(DEV, "Remote failed to finish a request within ko-count * timeout\n");
 		_drbd_set_state(_NS(mdev, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
 	}
-	if (dt && req->rq_state & RQ_LOCAL_PENDING &&
+	if (dt && req->rq_state & RQ_LOCAL_PENDING && req->w.mdev == mdev &&
 		 time_after(now, req->start_time + dt) &&
 		!time_in_range(now, mdev->last_reattach_jif, mdev->last_reattach_jif + dt)) {
 		dev_warn(DEV, "Local backing device failed to meet the disk-timeout\n");
 		__drbd_chk_io_error(mdev, DRBD_FORCE_DETACH);
 	}
 	nt = (time_after(now, req->start_time + et) ? now : req->start_time) + et;
-	spin_unlock_irq(&mdev->req_lock);
+	spin_unlock_irq(&tconn->req_lock);
 	mod_timer(&mdev->request_timer, nt);
 }