block: fix problem with sending down discard that isn't of correct granularity

If the queue doesn't have a limit set, or it just set UINT_MAX like
we default to, we coud be sending down a discard request that isn't
of the correct granularity if the block size is > 512b.

Fix this by adjusting max_discard_sectors down to the proper
alignment.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/block/blk-lib.c b/block/blk-lib.c
index e16185b0d8e1..5d793e143f3c 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -41,6 +41,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
         struct request_queue *q = bdev_get_queue(bdev);
         int type = flags & BLKDEV_IFL_BARRIER ?
                 DISCARD_BARRIER : DISCARD_NOBARRIER;
+        unsigned int max_discard_sectors;
         struct bio *bio;
         int ret = 0;
 
@@ -50,10 +51,18 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
         if (!blk_queue_discard(q))
                 return -EOPNOTSUPP;
 
-        while (nr_sects && !ret) {
-                unsigned int max_discard_sectors =
-                        min(q->limits.max_discard_sectors, UINT_MAX >> 9);
+        /*
+         * Ensure that max_discard_sectors is of the proper
+         * granularity
+         */
+        max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
+        if (q->limits.discard_granularity) {
+                unsigned int disc_sects = q->limits.discard_granularity >> 9;
 
+                max_discard_sectors &= ~(disc_sects - 1);
+        }
+
+        while (nr_sects && !ret) {
                 bio = bio_alloc(gfp_mask, 1);
                 if (!bio) {
                         ret = -ENOMEM;