block: free sched's request pool in blk_cleanup_queue

In theory, IO scheduler belongs to request queue, and the request pool
of sched tags belongs to the request queue too.

However, the current tags allocation interfaces are re-used for both
driver tags and sched tags, and driver tags is definitely host wide,
and doesn't belong to any request queue, same with its request pool.
So we need tagset instance for freeing request of sched tags.

Meantime, blk_mq_free_tag_set() often follows blk_cleanup_queue() in case
of non-BLK_MQ_F_TAG_SHARED, this way requires that request pool of sched
tags to be freed before calling blk_mq_free_tag_set().

Commit 47cdee29ef9d94e ("block: move blk_exit_queue into __blk_release_queue")
moves blk_exit_queue into __blk_release_queue for simplying the fast
path in generic_make_request(), then causes oops during freeing requests
of sched tags in __blk_release_queue().

Fix the above issue by move freeing request pool of sched tags into
blk_cleanup_queue(), this way is safe becasue queue has been frozen and no any
in-queue requests at that time. Freeing sched tags has to be kept in queue's
release handler becasue there might be un-completed dispatch activity
which might refer to sched tags.

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Christoph Hellwig <hch@lst.de>
Fixes: 47cdee29ef9d94e485eb08f962c74943023a5271 ("block: move blk_exit_queue into __blk_release_queue")
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 13 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index ee1b35fe8572..8340f69670d8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -320,6 +320,19 @@ void blk_cleanup_queue(struct request_queue *q)
 	if (queue_is_mq(q))
 		blk_mq_exit_queue(q);
 
+	/*
+	 * In theory, request pool of sched_tags belongs to request queue.
+	 * However, the current implementation requires tag_set for freeing
+	 * requests, so free the pool now.
+	 *
+	 * Queue has become frozen, there can't be any in-queue requests, so
+	 * it is safe to free requests now.
+	 */
+	mutex_lock(&q->sysfs_lock);
+	if (q->elevator)
+		blk_mq_sched_free_requests(q);
+	mutex_unlock(&q->sysfs_lock);
+
 	percpu_ref_exit(&q->q_usage_counter);
 
 	/* @q is and will stay empty, shutdown and put */