block: fix infinite loop if the device loses discard capability

If __blkdev_issue_discard is in progress and a device mapper device is
reloaded with a table that doesn't support discard,
q->limits.max_discard_sectors is set to zero. This results in infinite
loop in __blkdev_issue_discard.

This patch checks if max_discard_sectors is zero and aborts with
-EOPNOTSUPP.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Zdenek Kabelac <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 8faa70f..d1b9dd0 100644 (file)
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -68,6 +68,8 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                 */
                req_sects = min_t(sector_t, nr_sects,
                                        q->limits.max_discard_sectors);
+               if (!req_sects)
+                       goto fail;
                if (req_sects > UINT_MAX >> 9)
                        req_sects = UINT_MAX >> 9;
 
@@ -105,6 +107,14 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 
        *biop = bio;
        return 0;
+
+fail:
+       if (bio) {
+               submit_bio_wait(bio);
+               bio_put(bio);
+       }
+       *biop = NULL;
+       return -EOPNOTSUPP;
 }
 EXPORT_SYMBOL(__blkdev_issue_discard);