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Commit 6ff18507 authored by Ming Lei's avatar Ming Lei Committed by Greg Kroah-Hartman
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blk-mq: don't hold q->sysfs_lock in blk_mq_map_swqueue 



commit c6ba933358f0d7a6a042b894dba20cc70396a6d3 upstream.

blk_mq_map_swqueue() is called from blk_mq_init_allocated_queue()
and blk_mq_update_nr_hw_queues(). For the former caller, the kobject
isn't exposed to userspace yet. For the latter caller, hctx sysfs entries
and debugfs are un-registered before updating nr_hw_queues.

On the other hand, commit 2f8f1336a48b ("blk-mq: always free hctx after
request queue is freed") moves freeing hctx into queue's release
handler, so there won't be race with queue release path too.

So don't hold q->sysfs_lock in blk_mq_map_swqueue().

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarJack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 44b07600

block/blk-mq.c

+0 −7
Original line number Diff line number Diff line
@@ -2324,11 +2324,6 @@ static void blk_mq_map_swqueue(struct request_queue *q) 
	struct blk_mq_ctx *ctx;

	struct blk_mq_tag_set *set = q->tag_set;



	/*

	 * Avoid others reading imcomplete hctx->cpumask through sysfs

	 */

	mutex_lock(&q->sysfs_lock);



	queue_for_each_hw_ctx(q, hctx, i) {

		cpumask_clear(hctx->cpumask);

		hctx->nr_ctx = 0;
@@ -2362,8 +2357,6 @@ static void blk_mq_map_swqueue(struct request_queue *q) 
		hctx->ctxs[hctx->nr_ctx++] = ctx;

	}



	mutex_unlock(&q->sysfs_lock);



	queue_for_each_hw_ctx(q, hctx, i) {

		/*

		 * If no software queues are mapped to this hardware queue,