This is a note to let you know that I've just added the patch titled md/raid1: only allocate write behind bio for WriteMostly device to the 5.14-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-only-allocate-write-behind-bio-for-writemostly-device.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From fd3b6975e9c11c4fa00965f82a0bfbb3b7b44101 Mon Sep 17 00:00:00 2001 From: Guoqing Jiang <guoqing.jiang@xxxxxxxxx> Date: Mon, 4 Oct 2021 23:34:48 +0800 Subject: md/raid1: only allocate write behind bio for WriteMostly device From: Guoqing Jiang <guoqing.jiang@xxxxxxxxx> commit fd3b6975e9c11c4fa00965f82a0bfbb3b7b44101 upstream. Commit 6607cd319b6b91bff94e90f798a61c031650b514 ("raid1: ensure write behind bio has less than BIO_MAX_VECS sectors") tried to guarantee the size of behind bio is not bigger than BIO_MAX_VECS sectors. Unfortunately the same calltrace still could happen since an array could enable write-behind without write mostly device. To match the manpage of mdadm (which says "write-behind is only attempted on drives marked as write-mostly"), we need to check WriteMostly flag to avoid such unexpected behavior. [1]. https://bugzilla.kernel.org/show_bug.cgi?id=213181#c25 Cc: stable@xxxxxxxxxxxxxxx # v5.12+ Cc: Jens Stutte <jens@xxxxxxxxxxxxxxxxxx> Reported-by: Jens Stutte <jens@xxxxxxxxxxxxxxxxxx> Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxx> Signed-off-by: Song Liu <songliubraving@xxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/raid1.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -1496,7 +1496,7 @@ static void raid1_write_request(struct m if (!r1_bio->bios[i]) continue; - if (first_clone) { + if (first_clone && test_bit(WriteMostly, &rdev->flags)) { /* do behind I/O ? * Not if there are too many, or cannot * allocate memory, or a reader on WriteMostly Patches currently in stable-queue which might be from guoqing.jiang@xxxxxxxxx are queue-5.14/md-raid1-only-allocate-write-behind-bio-for-writemostly-device.patch