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

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>
This commit is contained in:
Mike Snitzer 2017-06-20 19:14:30 -04:00
parent 7def52b78a
commit feb7695fe9
1 changed files with 2 additions and 2 deletions
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4
drivers/md/dm-io.c
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@ -317,8 +317,8 @@ static void do_region(int op, int op_flags, unsigned region,
else if (op == REQ_OP_WRITE_SAME)
special_cmd_max_sectors = q->limits.max_write_same_sectors;
if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES ||
op == REQ_OP_WRITE_SAME) &&
special_cmd_max_sectors == 0) {
op == REQ_OP_WRITE_SAME) && special_cmd_max_sectors == 0) {
atomic_inc(&io->count);
dec_count(io, region, -EOPNOTSUPP);
return;
}