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 15ec4db194d1..0088bf60f368 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 dfb1b3a43a5d..d0ee7edc9be8 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 f759ad4584c3..187fd2c1a15d 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 7b2ec5908413..8cb0c27f2654 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 9324488f23f0..ee338bfde18b 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 */