block: Complain if queue_flag_(set|clear)_unlocked() is abused

Since it is not safe to use queue_flag_(set|clear)_unlocked()
without holding the queue lock after the sysfs entries for a
queue have been created, complain if this happens.

Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blkdev.h

@@ -728,12 +728,18 @@ static inline void queue_lockdep_assert_held(struct request_queue *q)
 static inline void queue_flag_set_unlocked(unsigned int flag,
 					   struct request_queue *q)
 {
+	if (test_bit(QUEUE_FLAG_INIT_DONE, &q->queue_flags) &&
+	    kref_read(&q->kobj.kref))
+		lockdep_assert_held(q->queue_lock);
 	__set_bit(flag, &q->queue_flags);
 }
 
 static inline void queue_flag_clear_unlocked(unsigned int flag,
 					     struct request_queue *q)
 {
+	if (test_bit(QUEUE_FLAG_INIT_DONE, &q->queue_flags) &&
+	    kref_read(&q->kobj.kref))
+		lockdep_assert_held(q->queue_lock);
 	__clear_bit(flag, &q->queue_flags);
 }