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authorDarrick J. Wong <darrick.wong@oracle.com>2015-02-13 11:05:37 -0800
committerMike Snitzer <snitzer@redhat.com>2015-02-13 19:51:09 -0500
commit37527b869207ad4c208b1e13967d69b8bba1fbf9 (patch)
treec9fd548b9cbc27abddb9e6843f3e62f769d199ff /drivers/md/dm-io.c
parentf2ed51ac64611d717d1917820a01930174c2f236 (diff)
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dm io: reject unsupported DISCARD requests with EOPNOTSUPP
I created a dm-raid1 device backed by a device that supports DISCARD and another device that does NOT support DISCARD with the following dm configuration: # echo '0 2048 mirror core 1 512 2 /dev/sda 0 /dev/sdb 0' | dmsetup create moo # lsblk -D NAME DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO sda 0 4K 1G 0 `-moo (dm-0) 0 4K 1G 0 sdb 0 0B 0B 0 `-moo (dm-0) 0 4K 1G 0 Notice that the mirror device /dev/mapper/moo advertises DISCARD support even though one of the mirror halves doesn't. If I issue a DISCARD request (via fstrim, mount -o discard, or ioctl BLKDISCARD) through the mirror, kmirrord gets stuck in an infinite loop in do_region() when it tries to issue a DISCARD request to sdb. The problem is that when we call do_region() against sdb, num_sectors is set to zero because q->limits.max_discard_sectors is zero. Therefore, "remaining" never decreases and the loop never terminates. To fix this: before entering the loop, check for the combination of REQ_DISCARD and no discard and return -EOPNOTSUPP to avoid hanging up the mirror device. This bug was found by the unfortunate coincidence of pvmove and a discard operation in the RHEL 6.5 kernel; upstream is also affected. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Acked-by: "Martin K. Petersen" <martin.petersen@oracle.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/md/dm-io.c')
-rw-r--r--drivers/md/dm-io.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index c09359db3a90..37de0173b6d2 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -290,6 +290,12 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where,
unsigned short logical_block_size = queue_logical_block_size(q);
sector_t num_sectors;
+ /* Reject unsupported discard requests */
+ if ((rw & REQ_DISCARD) && !blk_queue_discard(q)) {
+ dec_count(io, region, -EOPNOTSUPP);
+ return;
+ }
+
/*
* where->count may be zero if rw holds a flush and we need to
* send a zero-sized flush.