This is a note to let you know that I've just added the patch titled md/raid1: fix missing bitmap update w/o WriteMostly devices to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: md-raid1-fix-missing-bitmap-update-w-o-writemostly-devices.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 46669e8616c649c71c4cfcd712fd3d107e771380 Mon Sep 17 00:00:00 2001 From: Song Liu <song@xxxxxxxxxx> Date: Mon, 3 Jan 2022 13:49:36 -0800 Subject: md/raid1: fix missing bitmap update w/o WriteMostly devices From: Song Liu <song@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx # v5.12+ Cc: Guoqing Jiang <guoqing.jiang@xxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Reported-by: Norbert Warmuth <nwarmuth@xxxxxxxxxxx> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Song Liu <song@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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)) { Patches currently in stable-queue which might be from song@xxxxxxxxxx are queue-5.15/md-raid1-fix-missing-bitmap-update-w-o-writemostly-devices.patch