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md/raid1: only allocate write behind bio for WriteMostly device

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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@vger.kernel.org # v5.12+
Cc: Jens Stutte <jens@chianterastutte.eu>
Reported-by: Jens Stutte <jens@chianterastutte.eu>
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Guoqing Jiang 2021-10-04 23:34:48 +08:00 committed by Greg Kroah-Hartman
parent 805d775fe6
commit 3c0049a01b
1 changed files with 1 additions and 1 deletions
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2
drivers/md/raid1.c
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@ -1496,7 +1496,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
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