Merge branch 'stable/for-jens-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen into for-3.3/drivers

5 files changed, 170 insertions, 112 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 15ec4db194d..0088bf60f36 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -39,9 +39,6 @@
 #include <linux/list.h>
 #include <linux/delay.h>
 #include <linux/freezer.h>
-#include <linux/loop.h>
-#include <linux/falloc.h>
-#include <linux/fs.h>
 
 #include <xen/events.h>
 #include <xen/page.h>
@@ -362,7 +359,7 @@ static int xen_blkbk_map(struct blkif_request *req,
 {
 	struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	int i;
-	int nseg = req->nr_segments;
+	int nseg = req->u.rw.nr_segments;
 	int ret = 0;
 
 	/*
@@ -416,30 +413,25 @@ static int xen_blkbk_map(struct blkif_request *req,
 	return ret;
 }
 
-static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
+static int dispatch_discard_io(struct xen_blkif *blkif,
+				struct blkif_request *req)
 {
 	int err = 0;
 	int status = BLKIF_RSP_OKAY;
 	struct block_device *bdev = blkif->vbd.bdev;
 
-	if (blkif->blk_backend_type == BLKIF_BACKEND_PHY)
-		/* just forward the discard request */
+	blkif->st_ds_req++;
+
+	xen_blkif_get(blkif);
+	if (blkif->blk_backend_type == BLKIF_BACKEND_PHY ||
+	    blkif->blk_backend_type == BLKIF_BACKEND_FILE) {
+		unsigned long secure = (blkif->vbd.discard_secure &&
+			(req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
+			BLKDEV_DISCARD_SECURE : 0;
 		err = blkdev_issue_discard(bdev,
 				req->u.discard.sector_number,
 				req->u.discard.nr_sectors,
-				GFP_KERNEL, 0);
-	else if (blkif->blk_backend_type == BLKIF_BACKEND_FILE) {
-		/* punch a hole in the backing file */
-		struct loop_device *lo = bdev->bd_disk->private_data;
-		struct file *file = lo->lo_backing_file;
-
-		if (file->f_op->fallocate)
-			err = file->f_op->fallocate(file,
-				FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
-				req->u.discard.sector_number << 9,
-				req->u.discard.nr_sectors << 9);
-		else
-			err = -EOPNOTSUPP;
+				GFP_KERNEL, secure);
 	} else
 		err = -EOPNOTSUPP;
 
@@ -449,7 +441,9 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
 	} else if (err)
 		status = BLKIF_RSP_ERROR;
 
-	make_response(blkif, req->id, req->operation, status);
+	make_response(blkif, req->u.discard.id, req->operation, status);
+	xen_blkif_put(blkif);
+	return err;
 }
 
 static void xen_blk_drain_io(struct xen_blkif *blkif)
@@ -573,8 +567,11 @@ __do_block_io_op(struct xen_blkif *blkif)
 
 		/* Apply all sanity checks to /private copy/ of request. */
 		barrier();
-
-		if (dispatch_rw_block_io(blkif, &req, pending_req))
+		if (unlikely(req.operation == BLKIF_OP_DISCARD)) {
+			free_req(pending_req);
+			if (dispatch_discard_io(blkif, &req))
+				break;
+		} else if (dispatch_rw_block_io(blkif, &req, pending_req))
 			break;
 
 		/* Yield point for this unbounded loop. */
@@ -633,10 +630,6 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 		blkif->st_f_req++;
 		operation = WRITE_FLUSH;
 		break;
-	case BLKIF_OP_DISCARD:
-		blkif->st_ds_req++;
-		operation = REQ_DISCARD;
-		break;
 	default:
 		operation = 0; /* make gcc happy */
 		goto fail_response;
@@ -644,9 +637,9 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	}
 
 	/* Check that the number of segments is sane. */
-	nseg = req->nr_segments;
-	if (unlikely(nseg == 0 && operation != WRITE_FLUSH &&
-				operation != REQ_DISCARD) ||
+	nseg = req->u.rw.nr_segments;
+
+	if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
 	    unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
 		pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
 			 nseg);
@@ -654,12 +647,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 		goto fail_response;
 	}
 
-	preq.dev           = req->handle;
+	preq.dev           = req->u.rw.handle;
 	preq.sector_number = req->u.rw.sector_number;
 	preq.nr_sects      = 0;
 
 	pending_req->blkif     = blkif;
-	pending_req->id        = req->id;
+	pending_req->id        = req->u.rw.id;
 	pending_req->operation = req->operation;
 	pending_req->status    = BLKIF_RSP_OKAY;
 	pending_req->nr_pages  = nseg;
@@ -707,7 +700,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	 * the hypercall to unmap the grants - that is all done in
 	 * xen_blkbk_unmap.
 	 */
-	if (operation != REQ_DISCARD && xen_blkbk_map(req, pending_req, seg))
+	if (xen_blkbk_map(req, pending_req, seg))
 		goto fail_flush;
 
 	/*
@@ -739,23 +732,16 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 
 	/* This will be hit if the operation was a flush or discard. */
 	if (!bio) {
-		BUG_ON(operation != WRITE_FLUSH && operation != REQ_DISCARD);
+		BUG_ON(operation != WRITE_FLUSH);
 
-		if (operation == WRITE_FLUSH) {
-			bio = bio_alloc(GFP_KERNEL, 0);
-			if (unlikely(bio == NULL))
-				goto fail_put_bio;
+		bio = bio_alloc(GFP_KERNEL, 0);
+		if (unlikely(bio == NULL))
+			goto fail_put_bio;
 
-			biolist[nbio++] = bio;
-			bio->bi_bdev    = preq.bdev;
-			bio->bi_private = pending_req;
-			bio->bi_end_io  = end_block_io_op;
-		} else if (operation == REQ_DISCARD) {
-			xen_blk_discard(blkif, req);
-			xen_blkif_put(blkif);
-			free_req(pending_req);
-			return 0;
-		}
+		biolist[nbio++] = bio;
+		bio->bi_bdev    = preq.bdev;
+		bio->bi_private = pending_req;
+		bio->bi_end_io  = end_block_io_op;
 	}
 
 	/*
@@ -784,7 +770,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 	xen_blkbk_unmap(pending_req);
  fail_response:
 	/* Haven't submitted any bio's yet. */
-	make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
+	make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
 	free_req(pending_req);
 	msleep(1); /* back off a bit */
 	return -EIO;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dfb1b3a43a5..d0ee7edc9be 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -60,58 +60,66 @@ struct blkif_common_response {
 	char dummy;
 };
 
-/* i386 protocol version */
-#pragma pack(push, 4)
-
 struct blkif_x86_32_request_rw {
+	uint8_t        nr_segments;  /* number of segments                   */
+	blkif_vdev_t   handle;       /* only for read/write requests         */
+	uint64_t       id;           /* private guest value, echoed in resp  */
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
 	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-};
+} __attribute__((__packed__));
 
 struct blkif_x86_32_request_discard {
+	uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
+	blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
+	uint64_t       id;           /* private guest value, echoed in resp  */
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
-	uint64_t nr_sectors;
-};
+	uint64_t       nr_sectors;
+} __attribute__((__packed__));
 
 struct blkif_x86_32_request {
 	uint8_t        operation;    /* BLKIF_OP_???                         */
-	uint8_t        nr_segments;  /* number of segments                   */
-	blkif_vdev_t   handle;       /* only for read/write requests         */
-	uint64_t       id;           /* private guest value, echoed in resp  */
 	union {
 		struct blkif_x86_32_request_rw rw;
 		struct blkif_x86_32_request_discard discard;
 	} u;
-};
+} __attribute__((__packed__));
+
+/* i386 protocol version */
+#pragma pack(push, 4)
 struct blkif_x86_32_response {
 	uint64_t        id;              /* copied from request */
 	uint8_t         operation;       /* copied from request */
 	int16_t         status;          /* BLKIF_RSP_???       */
 };
 #pragma pack(pop)
-
 /* x86_64 protocol version */
 
 struct blkif_x86_64_request_rw {
+	uint8_t        nr_segments;  /* number of segments                   */
+	blkif_vdev_t   handle;       /* only for read/write requests         */
+	uint32_t       _pad1;        /* offsetof(blkif_reqest..,u.rw.id)==8  */
+	uint64_t       id;
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
 	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-};
+} __attribute__((__packed__));
 
 struct blkif_x86_64_request_discard {
+	uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero         */
+	blkif_vdev_t   _pad1;        /* was "handle" for read/write requests */
+        uint32_t       _pad2;        /* offsetof(blkif_..,u.discard.id)==8   */
+	uint64_t       id;
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
-	uint64_t nr_sectors;
-};
+	uint64_t       nr_sectors;
+} __attribute__((__packed__));
 
 struct blkif_x86_64_request {
 	uint8_t        operation;    /* BLKIF_OP_???                         */
-	uint8_t        nr_segments;  /* number of segments                   */
-	blkif_vdev_t   handle;       /* only for read/write requests         */
-	uint64_t       __attribute__((__aligned__(8))) id;
 	union {
 		struct blkif_x86_64_request_rw rw;
 		struct blkif_x86_64_request_discard discard;
 	} u;
-};
+} __attribute__((__packed__));
+
 struct blkif_x86_64_response {
 	uint64_t       __attribute__((__aligned__(8))) id;
 	uint8_t         operation;       /* copied from request */
@@ -156,6 +164,7 @@ struct xen_vbd {
 	/* Cached size parameter. */
 	sector_t		size;
 	bool			flush_support;
+	bool			discard_secure;
 };
 
 struct backend_info;
@@ -237,22 +246,23 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
 {
 	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
 	dst->operation = src->operation;
-	dst->nr_segments = src->nr_segments;
-	dst->handle = src->handle;
-	dst->id = src->id;
 	switch (src->operation) {
 	case BLKIF_OP_READ:
 	case BLKIF_OP_WRITE:
 	case BLKIF_OP_WRITE_BARRIER:
 	case BLKIF_OP_FLUSH_DISKCACHE:
+		dst->u.rw.nr_segments = src->u.rw.nr_segments;
+		dst->u.rw.handle = src->u.rw.handle;
+		dst->u.rw.id = src->u.rw.id;
 		dst->u.rw.sector_number = src->u.rw.sector_number;
 		barrier();
-		if (n > dst->nr_segments)
-			n = dst->nr_segments;
+		if (n > dst->u.rw.nr_segments)
+			n = dst->u.rw.nr_segments;
 		for (i = 0; i < n; i++)
 			dst->u.rw.seg[i] = src->u.rw.seg[i];
 		break;
 	case BLKIF_OP_DISCARD:
+		dst->u.discard.flag = src->u.discard.flag;
 		dst->u.discard.sector_number = src->u.discard.sector_number;
 		dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
 		break;
@@ -266,22 +276,23 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
 {
 	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
 	dst->operation = src->operation;
-	dst->nr_segments = src->nr_segments;
-	dst->handle = src->handle;
-	dst->id = src->id;
 	switch (src->operation) {
 	case BLKIF_OP_READ:
 	case BLKIF_OP_WRITE:
 	case BLKIF_OP_WRITE_BARRIER:
 	case BLKIF_OP_FLUSH_DISKCACHE:
+		dst->u.rw.nr_segments = src->u.rw.nr_segments;
+		dst->u.rw.handle = src->u.rw.handle;
+		dst->u.rw.id = src->u.rw.id;
 		dst->u.rw.sector_number = src->u.rw.sector_number;
 		barrier();
-		if (n > dst->nr_segments)
-			n = dst->nr_segments;
+		if (n > dst->u.rw.nr_segments)
+			n = dst->u.rw.nr_segments;
 		for (i = 0; i < n; i++)
 			dst->u.rw.seg[i] = src->u.rw.seg[i];
 		break;
 	case BLKIF_OP_DISCARD:
+		dst->u.discard.flag = src->u.discard.flag;
 		dst->u.discard.sector_number = src->u.discard.sector_number;
 		dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
 		break;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index f759ad4584c..187fd2c1a15 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -338,6 +338,9 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 	if (q && q->flush_flags)
 		vbd->flush_support = true;
 
+	if (q && blk_queue_secdiscard(q))
+		vbd->discard_secure = true;
+
 	DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 		handle, blkif->domid);
 	return 0;
@@ -420,6 +423,15 @@ int xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 				state = 1;
 				blkif->blk_backend_type = BLKIF_BACKEND_PHY;
 			}
+			/* Optional. */
+			err = xenbus_printf(xbt, dev->nodename,
+				"discard-secure", "%d",
+				blkif->vbd.discard_secure);
+			if (err) {
+				xenbus_dev_fatal(dev, err,
+					"writting discard-secure");
+				goto kfree;
+			}
 		}
 	} else {
 		err = PTR_ERR(type);
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7b2ec590841..8cb0c27f265 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -98,7 +98,8 @@ struct blkfront_info
 	unsigned long shadow_free;
 	unsigned int feature_flush;
 	unsigned int flush_op;
-	unsigned int feature_discard;
+	unsigned int feature_discard:1;
+	unsigned int feature_secdiscard:1;
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
 	int is_ready;
@@ -135,15 +136,15 @@ static int get_id_from_freelist(struct blkfront_info *info)
 {
 	unsigned long free = info->shadow_free;
 	BUG_ON(free >= BLK_RING_SIZE);
-	info->shadow_free = info->shadow[free].req.id;
-	info->shadow[free].req.id = 0x0fffffee; /* debug */
+	info->shadow_free = info->shadow[free].req.u.rw.id;
+	info->shadow[free].req.u.rw.id = 0x0fffffee; /* debug */
 	return free;
 }
 
 static void add_id_to_freelist(struct blkfront_info *info,
 			       unsigned long id)
 {
-	info->shadow[id].req.id  = info->shadow_free;
+	info->shadow[id].req.u.rw.id  = info->shadow_free;
 	info->shadow[id].request = NULL;
 	info->shadow_free = id;
 }
@@ -156,7 +157,7 @@ static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
 	if (end > nr_minors) {
 		unsigned long *bitmap, *old;
 
-		bitmap = kzalloc(BITS_TO_LONGS(end) * sizeof(*bitmap),
+		bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap),
 				 GFP_KERNEL);
 		if (bitmap == NULL)
 			return -ENOMEM;
@@ -287,9 +288,9 @@ static int blkif_queue_request(struct request *req)
 	id = get_id_from_freelist(info);
 	info->shadow[id].request = req;
 
-	ring_req->id = id;
+	ring_req->u.rw.id = id;
 	ring_req->u.rw.sector_number = (blkif_sector_t)blk_rq_pos(req);
-	ring_req->handle = info->handle;
+	ring_req->u.rw.handle = info->handle;
 
 	ring_req->operation = rq_data_dir(req) ?
 		BLKIF_OP_WRITE : BLKIF_OP_READ;
@@ -305,16 +306,21 @@ static int blkif_queue_request(struct request *req)
 		ring_req->operation = info->flush_op;
 	}
 
-	if (unlikely(req->cmd_flags & REQ_DISCARD)) {
+	if (unlikely(req->cmd_flags & (REQ_DISCARD | REQ_SECURE))) {
 		/* id, sector_number and handle are set above. */
 		ring_req->operation = BLKIF_OP_DISCARD;
-		ring_req->nr_segments = 0;
 		ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
+		if ((req->cmd_flags & REQ_SECURE) && info->feature_secdiscard)
+			ring_req->u.discard.flag = BLKIF_DISCARD_SECURE;
+		else
+			ring_req->u.discard.flag = 0;
 	} else {
-		ring_req->nr_segments = blk_rq_map_sg(req->q, req, info->sg);
-		BUG_ON(ring_req->nr_segments > BLKIF_MAX_SEGMENTS_PER_REQUEST);
+		ring_req->u.rw.nr_segments = blk_rq_map_sg(req->q, req,
+							   info->sg);
+		BUG_ON(ring_req->u.rw.nr_segments >
+		       BLKIF_MAX_SEGMENTS_PER_REQUEST);
 
-		for_each_sg(info->sg, sg, ring_req->nr_segments, i) {
+		for_each_sg(info->sg, sg, ring_req->u.rw.nr_segments, i) {
 			buffer_mfn = pfn_to_mfn(page_to_pfn(sg_page(sg)));
 			fsect = sg->offset >> 9;
 			lsect = fsect + (sg->length >> 9) - 1;
@@ -424,6 +430,8 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
 		blk_queue_max_discard_sectors(rq, get_capacity(gd));
 		rq->limits.discard_granularity = info->discard_granularity;
 		rq->limits.discard_alignment = info->discard_alignment;
+		if (info->feature_secdiscard)
+			queue_flag_set_unlocked(QUEUE_FLAG_SECDISCARD, rq);
 	}
 
 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
@@ -705,7 +713,9 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 static void blkif_completion(struct blk_shadow *s)
 {
 	int i;
-	for (i = 0; i < s->req.nr_segments; i++)
+	/* Do not let BLKIF_OP_DISCARD as nr_segment is in the same place
+	 * flag. */
+	for (i = 0; i < s->req.u.rw.nr_segments; i++)
 		gnttab_end_foreign_access(s->req.u.rw.seg[i].gref, 0, 0UL);
 }
 
@@ -736,7 +746,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 		id   = bret->id;
 		req  = info->shadow[id].request;
 
-		blkif_completion(&info->shadow[id]);
+		if (bret->operation != BLKIF_OP_DISCARD)
+			blkif_completion(&info->shadow[id]);
 
 		add_id_to_freelist(info, id);
 
@@ -749,7 +760,9 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 					   info->gd->disk_name);
 				error = -EOPNOTSUPP;
 				info->feature_discard = 0;
+				info->feature_secdiscard = 0;
 				queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
+				queue_flag_clear(QUEUE_FLAG_SECDISCARD, rq);
 			}
 			__blk_end_request_all(req, error);
 			break;
@@ -763,7 +776,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 				error = -EOPNOTSUPP;
 			}
 			if (unlikely(bret->status == BLKIF_RSP_ERROR &&
-				     info->shadow[id].req.nr_segments == 0)) {
+				     info->shadow[id].req.u.rw.nr_segments == 0)) {
 				printk(KERN_WARNING "blkfront: %s: empty write %s op failed\n",
 				       info->flush_op == BLKIF_OP_WRITE_BARRIER ?
 				       "barrier" :  "flush disk cache",
@@ -984,8 +997,8 @@ static int blkfront_probe(struct xenbus_device *dev,
 	INIT_WORK(&info->work, blkif_restart_queue);
 
 	for (i = 0; i < BLK_RING_SIZE; i++)
-		info->shadow[i].req.id = i+1;
-	info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+		info->shadow[i].req.u.rw.id = i+1;
+	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
 
 	/* Front end dir is a number, which is used as the id. */
 	info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
@@ -1019,9 +1032,9 @@ static int blkif_recover(struct blkfront_info *info)
 	/* Stage 2: Set up free list. */
 	memset(&info->shadow, 0, sizeof(info->shadow));
 	for (i = 0; i < BLK_RING_SIZE; i++)
-		info->shadow[i].req.id = i+1;
+		info->shadow[i].req.u.rw.id = i+1;
 	info->shadow_free = info->ring.req_prod_pvt;
-	info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+	info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
 
 	/* Stage 3: Find pending requests and requeue them. */
 	for (i = 0; i < BLK_RING_SIZE; i++) {
@@ -1034,17 +1047,19 @@ static int blkif_recover(struct blkfront_info *info)
 		*req = copy[i].req;
 
 		/* We get a new request id, and must reset the shadow state. */
-		req->id = get_id_from_freelist(info);
-		memcpy(&info->shadow[req->id], &copy[i], sizeof(copy[i]));
+		req->u.rw.id = get_id_from_freelist(info);
+		memcpy(&info->shadow[req->u.rw.id], &copy[i], sizeof(copy[i]));
 
+		if (req->operation != BLKIF_OP_DISCARD) {
 		/* Rewrite any grant references invalidated by susp/resume. */
-		for (j = 0; j < req->nr_segments; j++)
-			gnttab_grant_foreign_access_ref(
-				req->u.rw.seg[j].gref,
-				info->xbdev->otherend_id,
-				pfn_to_mfn(info->shadow[req->id].frame[j]),
-				rq_data_dir(info->shadow[req->id].request));
-		info->shadow[req->id].req = *req;
+			for (j = 0; j < req->u.rw.nr_segments; j++)
+				gnttab_grant_foreign_access_ref(
+					req->u.rw.seg[j].gref,
+					info->xbdev->otherend_id,
+					pfn_to_mfn(info->shadow[req->u.rw.id].frame[j]),
+					rq_data_dir(info->shadow[req->u.rw.id].request));
+		}
+		info->shadow[req->u.rw.id].req = *req;
 
 		info->ring.req_prod_pvt++;
 	}
@@ -1135,11 +1150,13 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 	char *type;
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
+	unsigned int discard_secure;
 
 	type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
 	if (IS_ERR(type))
 		return;
 
+	info->feature_secdiscard = 0;
 	if (strncmp(type, "phy", 3) == 0) {
 		err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
 			"discard-granularity", "%u", &discard_granularity,
@@ -1150,6 +1167,12 @@ static void blkfront_setup_discard(struct blkfront_info *info)
 			info->discard_granularity = discard_granularity;
 			info->discard_alignment = discard_alignment;
 		}
+		err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "discard-secure", "%d", &discard_secure,
+			    NULL);
+		if (!err)
+			info->feature_secdiscard = discard_secure;
+
 	} else if (strncmp(type, "file", 4) == 0)
 		info->feature_discard = 1;
 
diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
index 9324488f23f..ee338bfde18 100644
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -84,6 +84,21 @@ typedef uint64_t blkif_sector_t;
  *     e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc
  * http://www.seagate.com/staticfiles/support/disc/manuals/
  *     Interface%20manuals/100293068c.pdf
+ * The backend can optionally provide three extra XenBus attributes to
+ * further optimize the discard functionality:
+ * 'discard-aligment' - Devices that support discard functionality may
+ * internally allocate space in units that are bigger than the exported
+ * logical block size. The discard-alignment parameter indicates how many bytes
+ * the beginning of the partition is offset from the internal allocation unit's
+ * natural alignment.
+ * 'discard-granularity'  - Devices that support discard functionality may
+ * internally allocate space using units that are bigger than the logical block
+ * size. The discard-granularity parameter indicates the size of the internal
+ * allocation unit in bytes if reported by the device. Otherwise the
+ * discard-granularity will be set to match the device's physical block size.
+ * 'discard-secure' - All copies of the discarded sectors (potentially created
+ * by garbage collection) must also be erased.  To use this feature, the flag
+ * BLKIF_DISCARD_SECURE must be set in the blkif_request_trim.
  */
 #define BLKIF_OP_DISCARD           5
 
@@ -95,6 +110,12 @@ typedef uint64_t blkif_sector_t;
 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
 
 struct blkif_request_rw {
+	uint8_t        nr_segments;  /* number of segments                   */
+	blkif_vdev_t   handle;       /* only for read/write requests         */
+#ifdef CONFIG_X86_64
+	uint32_t       _pad1;	     /* offsetof(blkif_request,u.rw.id) == 8 */
+#endif
+	uint64_t       id;           /* private guest value, echoed in resp  */
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
 	struct blkif_request_segment {
 		grant_ref_t gref;        /* reference to I/O buffer frame        */
@@ -102,23 +123,28 @@ struct blkif_request_rw {
 		/* @last_sect: last sector in frame to transfer (inclusive).     */
 		uint8_t     first_sect, last_sect;
 	} seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
-};
+} __attribute__((__packed__));
 
 struct blkif_request_discard {
+	uint8_t        flag;         /* BLKIF_DISCARD_SECURE or zero.        */
+#define BLKIF_DISCARD_SECURE (1<<0)  /* ignored if discard-secure=0          */
+	blkif_vdev_t   _pad1;        /* only for read/write requests         */
+#ifdef CONFIG_X86_64
+	uint32_t       _pad2;        /* offsetof(blkif_req..,u.discard.id)==8*/
+#endif
+	uint64_t       id;           /* private guest value, echoed in resp  */
 	blkif_sector_t sector_number;
-	uint64_t nr_sectors;
-};
+	uint64_t       nr_sectors;
+	uint8_t        _pad3;
+} __attribute__((__packed__));
 
 struct blkif_request {
 	uint8_t        operation;    /* BLKIF_OP_???                         */
-	uint8_t        nr_segments;  /* number of segments                   */
-	blkif_vdev_t   handle;       /* only for read/write requests         */
-	uint64_t       id;           /* private guest value, echoed in resp  */
 	union {
 		struct blkif_request_rw rw;
 		struct blkif_request_discard discard;
 	} u;
-};
+} __attribute__((__packed__));
 
 struct blkif_response {
 	uint64_t        id;              /* copied from request */