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Commit 6936c12c authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm table: fix 'all_blk_mq' inconsistency when an empty table is loaded 



An earlier DM multipath table could have been build ontop of underlying
devices that were all using blk-mq.  In that case, if that active
multipath table is replaced with an empty DM multipath table (that
reflects all paths have failed) then it is important that the
'all_blk_mq' state of the active table is transfered to the new empty DM
table.  Otherwise dm-rq.c:dm_old_prep_tio() will incorrectly clone a
request that isn't needed by the DM multipath target when it is to issue
IO to an underlying blk-mq device.

Fixes: e83068a5 ("dm mpath: add optional "queue_mode" feature")
Cc: stable@vger.kernel.org # 4.8+
Reported-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Tested-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 6599c84e

drivers/md/dm-table.c

+13 −6
Original line number Diff line number Diff line
@@ -924,12 +924,6 @@ static int dm_table_determine_type(struct dm_table *t) 


	BUG_ON(!request_based); /* No targets in this table */



	if (list_empty(devices) && __table_type_request_based(live_md_type)) {

		/* inherit live MD type */

		t->type = live_md_type;

		return 0;

	}



	/*

	 * The only way to establish DM_TYPE_MQ_REQUEST_BASED is by

	 * having a compatible target use dm_table_set_type.
@@ -948,6 +942,19 @@ static int dm_table_determine_type(struct dm_table *t) 
		return -EINVAL;

	}



	if (list_empty(devices)) {

		int srcu_idx;

		struct dm_table *live_table = dm_get_live_table(t->md, &srcu_idx);



		/* inherit live table's type and all_blk_mq */

		if (live_table) {

			t->type = live_table->type;

			t->all_blk_mq = live_table->all_blk_mq;

		}

		dm_put_live_table(t->md, srcu_idx);

		return 0;

	}



	/* Non-request-stackable devices can't be used for request-based dm */

	list_for_each_entry(dd, devices, list) {

		struct request_queue *q = bdev_get_queue(dd->dm_dev->bdev);