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>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index e16185b..5d793e1 100644 (file)
--- 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;