dm table: fix 'all_blk_mq' inconsistency when an empty table is loaded (6936c12c) · Commits · 戴 / test

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: ("dm mpath: add optional "queue_mode" feature") Cc: stable@vger.kernel.org # 4.8+ Reported-by:

Bart Van Assche <bart.vanassche@sandisk.com> Tested-by:

Bart Van Assche <bart.vanassche@sandisk.com> Signed-off-by:

Mike Snitzer <snitzer@redhat.com>

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 @@ verify_rq_based:
		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);

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