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dm io: fix duplicate bio completion due to missing ref count

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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>
This commit is contained in:
Mike Snitzer 2017-06-20 19:14:30 -04:00 committed by Greg Kroah-Hartman
parent 6213c714a5
commit b6f93a1341
1 changed files with 1 additions and 0 deletions
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drivers/md/dm-io.c
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@ -302,6 +302,7 @@ static void do_region(int op, int op_flags, unsigned region,
special_cmd_max_sectors = q->limits.max_write_same_sectors;
if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_SAME) &&
special_cmd_max_sectors == 0) {
atomic_inc(&io->count);
dec_count(io, region, -EOPNOTSUPP);
return;
}