| Message ID | 20150213190537.GA5519@birch.djwong.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c index c09359d..37de017 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.
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. 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; 3.19 is also affected. v2: Remove the WRITE SAME part since dm won't allow it unless all component devices support it. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Cc: "Martin K. Petersen" <martin.petersen@oracle.com> Cc: Srinivas Eeda <srinivas.eeda@oracle.com> Cc: Todd Vierling <todd.vierling@oracle.com> --- drivers/md/dm-io.c | 6 ++++++ 1 file changed, 6 insertions(+) -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel