This is a note to let you know that I've just added the patch titled
dm io: fix duplicate bio completion due to missing ref count
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: dm-io-fix-duplicate-bio-completion-due-to-missing-ref-count.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From feb7695fe9fb83084aa29de0094774f4c9d4c9fc Mon Sep 17 00:00:00 2001
From: Mike Snitzer snitzer@redhat.com Date: Tue, 20 Jun 2017 19:14:30 -0400 Subject: dm io: fix duplicate bio completion due to missing ref count
From: Mike Snitzer snitzer@redhat.com
commit feb7695fe9fb83084aa29de0094774f4c9d4c9fc upstream.
If only a subset of the devices associated with multiple regions support a given special operation (eg. DISCARD) then the dec_count() that is used to set error for the region must increment the io->count.
Otherwise, when the dec_count() is called it can cause the dm-io caller's bio to be completed multiple times. As was reported against the dm-mirror target that had mirror legs with a mix of discard capabilities.
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=196077 Reported-by: Zhang Yi yizhan@redhat.com Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/dm-io.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/md/dm-io.c +++ b/drivers/md/dm-io.c @@ -300,6 +300,7 @@ static void do_region(int rw, unsigned r else if (rw & REQ_WRITE_SAME) special_cmd_max_sectors = q->limits.max_write_same_sectors; if ((rw & (REQ_DISCARD | REQ_WRITE_SAME)) && special_cmd_max_sectors == 0) { + atomic_inc(&io->count); dec_count(io, region, -EOPNOTSUPP); return; }
Patches currently in stable-queue which might be from snitzer@redhat.com are
queue-4.4/dm-io-fix-duplicate-bio-completion-due-to-missing-ref-count.patch