Commit feb7695f authored Jun 20, 2017 by Mike Snitzer

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>

parent 7def52b7

drivers/md/dm-io.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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