blk-mq: Make blk_mq_quiesce_tagset() hold the tag list mutex less long

Make sure that the tag_list_lock mutex is not held any longer than
necessary. This change reduces latency if e.g. blk_mq_quiesce_tagset()
is called concurrently from more than one thread. This function is used
by the NVMe core and also by the UFS driver.

Reported-by: Peter Wang <peter.wang@mediatek.com>
Cc: Chao Leng <lengchao@huawei.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 414dd48e882c ("blk-mq: add tagset quiesce interface")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20241022181617.2716173-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 022653320c18b9acbcfee086e404b2ccbaa8d8d0..e39319ff4ecbe61d062da6532ae7bc319b40df7d 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -283,8 +283,9 @@ void blk_mq_quiesce_tagset(struct blk_mq_tag_set *set)
                if (!blk_queue_skip_tagset_quiesce(q))
                        blk_mq_quiesce_queue_nowait(q);
        }
-       blk_mq_wait_quiesce_done(set);
        mutex_unlock(&set->tag_list_lock);
+
+       blk_mq_wait_quiesce_done(set);
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_tagset);