5 files changed, 36 insertions, 19 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index e5448131d4f1..988b63479b2f 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -372,7 +372,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                         nr_sects = 0;
                 }
                 bio_get(bio);
-                submit_bio(WRITE_DISCARD, bio);
+                submit_bio(DISCARD_BARRIER, bio);
 
                 /* Check if it failed immediately */
                 if (bio_flagged(bio, BIO_EOPNOTSUPP))
diff --git a/block/blk-core.c b/block/blk-core.c
index 1e143c4f9d34..1261516dd42a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1077,12 +1077,13 @@ void init_request_from_bio(struct request *req, struct bio *bio)
         /*
          * REQ_BARRIER implies no merging, but lets make it explicit
          */
-        if (unlikely(bio_barrier(bio)))
-                req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
         if (unlikely(bio_discard(bio))) {
-                req->cmd_flags |= (REQ_SOFTBARRIER | REQ_DISCARD);
+                req->cmd_flags |= REQ_DISCARD;
+                if (bio_barrier(bio))
+                        req->cmd_flags |= REQ_SOFTBARRIER;
                 req->q->prepare_discard_fn(req->q, req);
-        }
+        } else if (unlikely(bio_barrier(bio)))
+                req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
 
         if (bio_sync(bio))
                 req->cmd_flags |= REQ_RW_SYNC;
@@ -1114,7 +1115,8 @@ static int __make_request(struct request_queue *q, struct bio *bio)
         blk_queue_bounce(q, &bio);
 
         barrier = bio_barrier(bio);
-        if (unlikely(barrier) && (q->next_ordered == QUEUE_ORDERED_NONE)) {
+        if (unlikely(barrier) && bio_has_data(bio) &&
+            (q->next_ordered == QUEUE_ORDERED_NONE)) {
                 err = -EOPNOTSUPP;
                 goto end_io;
         }
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 5efc9e7a68b7..6cf8f0c70a51 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -11,7 +11,7 @@
 
 void blk_recalc_rq_sectors(struct request *rq, int nsect)
 {
-        if (blk_fs_request(rq)) {
+        if (blk_fs_request(rq) || blk_discard_rq(rq)) {
                 rq->hard_sector += nsect;
                 rq->hard_nr_sectors -= nsect;
 
@@ -131,13 +131,17 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
         if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
                 return 0;
 
-        if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
-                return 0;
         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
                 return 0;
 
+        if (!bio_has_data(bio))
+                return 1;
+
+        if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
+                return 0;
+
         /*
-         * bio and nxt are contigous in memory, check if the queue allows
+         * bio and nxt are contiguous in memory; check if the queue allows
          * these two to be merged into one
          */
         if (BIO_SEG_BOUNDARY(q, bio, nxt))
@@ -153,8 +157,9 @@ static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio,
                 blk_recount_segments(q, bio);
         if (!bio_flagged(nxt, BIO_SEG_VALID))
                 blk_recount_segments(q, nxt);
-        if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
-            BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size))
+        if (bio_has_data(bio) &&
+            (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
+             BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size)))
                 return 0;
         if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
                 return 0;
@@ -317,8 +322,9 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req,
         if (!bio_flagged(bio, BIO_SEG_VALID))
                 blk_recount_segments(q, bio);
         len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
-        if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))
-            && !BIOVEC_VIRT_OVERSIZE(len)) {
+        if (!bio_has_data(bio) || 
+            (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))
+             && !BIOVEC_VIRT_OVERSIZE(len))) {
                 int mergeable =  ll_new_mergeable(q, req, bio);
 
                 if (mergeable) {
@@ -356,8 +362,9 @@ int ll_front_merge_fn(struct request_queue *q, struct request *req,
                 blk_recount_segments(q, bio);
         if (!bio_flagged(req->bio, BIO_SEG_VALID))
                 blk_recount_segments(q, req->bio);
-        if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
-            !BIOVEC_VIRT_OVERSIZE(len)) {
+        if (!bio_has_data(bio) || 
+            (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
+             !BIOVEC_VIRT_OVERSIZE(len))) {
                 int mergeable =  ll_new_mergeable(q, req, bio);
 
                 if (mergeable) {
diff --git a/block/elevator.c b/block/elevator.c
index ed6f8f32d27e..4f5127054e3f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -75,6 +75,12 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio)
                 return 0;
 
         /*
+         * Don't merge file system requests and discard requests
+         */
+        if (bio_discard(bio) != bio_discard(rq->bio))
+                return 0;
+
+        /*
          * different data direction or already started, don't merge
          */
         if (bio_data_dir(bio) != rq_data_dir(rq))
@@ -438,6 +444,8 @@ void elv_dispatch_sort(struct request_queue *q, struct request *rq)
         list_for_each_prev(entry, &q->queue_head) {
                 struct request *pos = list_entry_rq(entry);
 
+                if (blk_discard_rq(rq) != blk_discard_rq(pos))
+                        break;
                 if (rq_data_dir(rq) != rq_data_dir(pos))
                         break;
                 if (pos->cmd_flags & stop_flags)
@@ -607,7 +615,7 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
                 break;
 
         case ELEVATOR_INSERT_SORT:
-                BUG_ON(!blk_fs_request(rq));
+                BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq));
                 rq->cmd_flags |= REQ_SORTED;
                 q->nr_sorted++;
                 if (rq_mergeable(rq)) {
@@ -692,7 +700,7 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where,
                  * this request is scheduling boundary, update
                  * end_sector
                  */
-                if (blk_fs_request(rq)) {
+                if (blk_fs_request(rq) || blk_discard_rq(rq)) {
                         q->end_sector = rq_end_sector(rq);
                         q->boundary_rq = rq;
                 }
diff --git a/block/ioctl.c b/block/ioctl.c
index 342298bb6080..375c57922b00 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -161,7 +161,7 @@ static int blk_ioctl_discard(struct block_device *bdev, uint64_t start,
                         bio->bi_size = len << 9;
                         len = 0;
                 }
-                submit_bio(WRITE_DISCARD, bio);
+                submit_bio(DISCARD_NOBARRIER, bio);
 
                 wait_for_completion(&wait);