From: Darrick J. Wong Date: Fri, 13 Feb 2015 19:05:37 +0000 (-0800) Subject: dm io: reject unsupported DISCARD requests with EOPNOTSUPP X-Git-Tag: fixes-v4.0-rc1~28^2~9 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=37527b869207ad4c208b1e13967d69b8bba1fbf9;p=pandora-kernel.git 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 Acked-by: "Martin K. Petersen" Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- Reading git-diff-tree failed