blk-mq: add new API of blk_mq_hctx_set_fq_lock_class

	kfree(fq->flush_rq);

	kfree(fq);

}

/*

 * Allow driver to set its own lock class to fq->mq_flush_lock for

 * avoiding lockdep complaint.

 *

 * flush_end_io() may be called recursively from some driver, such as

 * nvme-loop, so lockdep may complain 'possible recursive locking' because

 * all 'struct blk_flush_queue' instance share same mq_flush_lock lock class

 * key. We need to assign different lock class for these driver's

 * fq->mq_flush_lock for avoiding the lockdep warning.

 *

 * Use dynamically allocated lock class key for each 'blk_flush_queue'

 * instance is over-kill, and more worse it introduces horrible boot delay

 * issue because synchronize_rcu() is implied in lockdep_unregister_key which

 * is called for each hctx release. SCSI probing may synchronously create and

 * destroy lots of MQ request_queues for non-existent devices, and some robot

 * test kernel always enable lockdep option. It is observed that more than half

 * an hour is taken during SCSI MQ probe with per-fq lock class.

 */

void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx,

		struct lock_class_key *key)

{

	lockdep_set_class(&hctx->fq->mq_flush_lock, key);

}

EXPORT_SYMBOL_GPL(blk_mq_hctx_set_fq_lock_class);

#include <linux/blkdev.h>

#include <linux/sbitmap.h>

#include <linux/srcu.h>

#include <linux/lockdep.h>

struct blk_mq_tags;

struct blk_flush_queue;

}

blk_qc_t blk_mq_submit_bio(struct bio *bio);

void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx,

		struct lock_class_key *key);

#endif