From: Song Liu song@kernel.org
commit 46669e8616c649c71c4cfcd712fd3d107e771380 upstream.
commit [1] causes missing bitmap updates when there isn't any WriteMostly devices.
Detailed steps to reproduce by Norbert (which somehow didn't make to lore):
# setup md10 (raid1) with two drives (1 GByte sparse files) dd if=/dev/zero of=disk1 bs=1024k seek=1024 count=0 dd if=/dev/zero of=disk2 bs=1024k seek=1024 count=0
losetup /dev/loop11 disk1 losetup /dev/loop12 disk2
mdadm --create /dev/md10 --level=1 --raid-devices=2 /dev/loop11 /dev/loop12
# add bitmap (aka write-intent log) mdadm /dev/md10 --grow --bitmap=internal
echo check > /sys/block/md10/md/sync_action
root:# cat /sys/block/md10/md/mismatch_cnt 0 root:#
# remove member drive disk2 (loop12) mdadm /dev/md10 -f loop12 ; mdadm /dev/md10 -r loop12
# modify degraded md device dd if=/dev/urandom of=/dev/md10 bs=512 count=1
# no blocks recorded as out of sync on the remaining member disk1/loop11 root:# mdadm -X /dev/loop11 | grep Bitmap Bitmap : 16 bits (chunks), 0 dirty (0.0%) root:#
# re-add disk2, nothing synced because of empty bitmap mdadm /dev/md10 --re-add /dev/loop12
# check integrity again echo check > /sys/block/md10/md/sync_action
# disk1 and disk2 are no longer in sync, reads return differend data root:# cat /sys/block/md10/md/mismatch_cnt 128 root:#
# clean up mdadm -S /dev/md10 losetup -d /dev/loop11 losetup -d /dev/loop12 rm disk1 disk2
Fix this by moving the WriteMostly check to the if condition for alloc_behind_master_bio().
[1] commit fd3b6975e9c1 ("md/raid1: only allocate write behind bio for WriteMostly device") Fixes: fd3b6975e9c1 ("md/raid1: only allocate write behind bio for WriteMostly device") Cc: stable@vger.kernel.org # v5.12+ Cc: Guoqing Jiang guoqing.jiang@linux.dev Cc: Jens Axboe axboe@kernel.dk Reported-by: Norbert Warmuth nwarmuth@t-online.de Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Song Liu song@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/raid1.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -1496,12 +1496,13 @@ static void raid1_write_request(struct m if (!r1_bio->bios[i]) continue;
- if (first_clone && test_bit(WriteMostly, &rdev->flags)) { + if (first_clone) { /* do behind I/O ? * Not if there are too many, or cannot * allocate memory, or a reader on WriteMostly * is waiting for behind writes to flush */ if (bitmap && + test_bit(WriteMostly, &rdev->flags) && (atomic_read(&bitmap->behind_writes) < mddev->bitmap_info.max_write_behind) && !waitqueue_active(&bitmap->behind_wait)) {