blk-mq: Swap two calls in blk_mq_exit_queue()

[ Upstream commit 630ef623ed26c18a457cdc070cf24014e50129c2 ]

If a tag set is shared across request queues (e.g. SCSI LUNs) then the
block layer core keeps track of the number of active request queues in
tags->active_queues. blk_mq_tag_busy() and blk_mq_tag_idle() update that
atomic counter if the hctx flag BLK_MQ_F_TAG_QUEUE_SHARED is set. Make
sure that blk_mq_exit_queue() calls blk_mq_tag_idle() before that flag is
cleared by blk_mq_del_queue_tag_set().

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Fixes: 0d2602ca30e4 ("blk-mq: improve support for shared tags maps")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210513171529.7977-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 195526b93895e1f1ed97618504ee80bd7e4ffbd1..ae70b4809bec4db5eaf1753f85756c9d32b636b3 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2673,10 +2673,12 @@ EXPORT_SYMBOL(blk_mq_init_allocated_queue);
 /* tags can _not_ be used after returning from blk_mq_exit_queue */
 void blk_mq_exit_queue(struct request_queue *q)
 {
-       struct blk_mq_tag_set   *set = q->tag_set;
+       struct blk_mq_tag_set *set = q->tag_set;
 
-       blk_mq_del_queue_tag_set(q);
+       /* Checks hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED. */
        blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
+       /* May clear BLK_MQ_F_TAG_QUEUE_SHARED in hctx->flags. */
+       blk_mq_del_queue_tag_set(q);
 }
 
 /* Basically redo blk_mq_init_queue with queue frozen */