Commit 65d466b6 authored by Yu Kuai's avatar Yu Kuai Committed by Jens Axboe
Browse files

blk-mq-debugfs: warn about possible deadlock 



Creating new debugfs entries can trigger fs reclaim, hence we can't do
this with queue frozen, meanwhile, other locks that can be held while
queue is frozen should not be held as well.

Signed-off-by: default avatarYu Kuai <yukuai@fnnas.com>
Reviewed-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9d20fd6c

block/blk-mq-debugfs.c

+24 −7
Original line number Diff line number Diff line
@@ -608,9 +608,23 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = { 
	{},

};



static void debugfs_create_files(struct dentry *parent, void *data,

static void debugfs_create_files(struct request_queue *q, struct dentry *parent,

				 void *data,

				 const struct blk_mq_debugfs_attr *attr)

{

	lockdep_assert_held(&q->debugfs_mutex);

	/*

	 * Creating new debugfs entries with queue freezed has the risk of

	 * deadlock.

	 */

	WARN_ON_ONCE(q->mq_freeze_depth != 0);

	/*

	 * debugfs_mutex should not be nested under other locks that can be

	 * grabbed while queue is frozen.

	 */

	lockdep_assert_not_held(&q->elevator_lock);

	lockdep_assert_not_held(&q->rq_qos_mutex);



	if (IS_ERR_OR_NULL(parent))

		return;
@@ -624,7 +638,7 @@ void blk_mq_debugfs_register(struct request_queue *q) 
	struct blk_mq_hw_ctx *hctx;

	unsigned long i;



	debugfs_create_files(q->debugfs_dir, q, blk_mq_debugfs_queue_attrs);

	debugfs_create_files(q, q->debugfs_dir, q, blk_mq_debugfs_queue_attrs);



	queue_for_each_hw_ctx(q, hctx, i) {

		if (!hctx->debugfs_dir)
@@ -643,7 +657,8 @@ static void blk_mq_debugfs_register_ctx(struct blk_mq_hw_ctx *hctx, 
	snprintf(name, sizeof(name), "cpu%u", ctx->cpu);

	ctx_dir = debugfs_create_dir(name, hctx->debugfs_dir);



	debugfs_create_files(ctx_dir, ctx, blk_mq_debugfs_ctx_attrs);

	debugfs_create_files(hctx->queue, ctx_dir, ctx,

			     blk_mq_debugfs_ctx_attrs);

}



void blk_mq_debugfs_register_hctx(struct request_queue *q,
@@ -659,7 +674,8 @@ void blk_mq_debugfs_register_hctx(struct request_queue *q, 
	snprintf(name, sizeof(name), "hctx%u", hctx->queue_num);

	hctx->debugfs_dir = debugfs_create_dir(name, q->debugfs_dir);



	debugfs_create_files(hctx->debugfs_dir, hctx, blk_mq_debugfs_hctx_attrs);

	debugfs_create_files(q, hctx->debugfs_dir, hctx,

			     blk_mq_debugfs_hctx_attrs);



	hctx_for_each_ctx(hctx, ctx, i)

		blk_mq_debugfs_register_ctx(hctx, ctx);
@@ -712,7 +728,7 @@ void blk_mq_debugfs_register_sched(struct request_queue *q) 


	q->sched_debugfs_dir = debugfs_create_dir("sched", q->debugfs_dir);



	debugfs_create_files(q->sched_debugfs_dir, q, e->queue_debugfs_attrs);

	debugfs_create_files(q, q->sched_debugfs_dir, q, e->queue_debugfs_attrs);

}



void blk_mq_debugfs_unregister_sched(struct request_queue *q)
@@ -751,7 +767,8 @@ static void blk_mq_debugfs_register_rqos(struct rq_qos *rqos) 
							 q->debugfs_dir);



	rqos->debugfs_dir = debugfs_create_dir(dir_name, q->rqos_debugfs_dir);

	debugfs_create_files(rqos->debugfs_dir, rqos, rqos->ops->debugfs_attrs);

	debugfs_create_files(q, rqos->debugfs_dir, rqos,

			     rqos->ops->debugfs_attrs);

}



void blk_mq_debugfs_register_rq_qos(struct request_queue *q)
@@ -788,7 +805,7 @@ void blk_mq_debugfs_register_sched_hctx(struct request_queue *q, 


	hctx->sched_debugfs_dir = debugfs_create_dir("sched",

						     hctx->debugfs_dir);

	debugfs_create_files(hctx->sched_debugfs_dir, hctx,

	debugfs_create_files(q, hctx->sched_debugfs_dir, hctx,

			     e->hctx_debugfs_attrs);

}