Commit 14ef4965 authored by Nilay Shroff's avatar Nilay Shroff Committed by Jens Axboe
Browse files

block: fix nr_hw_queue update racing with disk addition/removal 



The nr_hw_queue update could potentially race with disk addtion/removal
while registering/unregistering hctx sysfs files. The __blk_mq_update_
nr_hw_queues() runs with q->tag_list_lock held and so to avoid it racing
with disk addition/removal we should acquire q->tag_list_lock while
registering/unregistering hctx sysfs files.

With this patch, blk_mq_sysfs_register() (called during disk addition)
and blk_mq_sysfs_unregister() (called during disk removal) now runs
with q->tag_list_lock held so that it avoids racing with __blk_mq_update
_nr_hw_queues().

Signed-off-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20250128143436.874357-3-nilay@linux.ibm.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fe662860

block/blk-mq-sysfs.c

+9 −8
Original line number Diff line number Diff line
@@ -225,25 +225,25 @@ int blk_mq_sysfs_register(struct gendisk *disk) 


	ret = kobject_add(q->mq_kobj, &disk_to_dev(disk)->kobj, "mq");

	if (ret < 0)

		goto out;

		return ret;



	kobject_uevent(q->mq_kobj, KOBJ_ADD);



	mutex_lock(&q->tag_set->tag_list_lock);

	queue_for_each_hw_ctx(q, hctx, i) {

		ret = blk_mq_register_hctx(hctx);

		if (ret)

			goto unreg;

			goto out_unreg;

	}

	mutex_unlock(&q->tag_set->tag_list_lock);

	return 0;





out:

	return ret;



unreg:

out_unreg:

	queue_for_each_hw_ctx(q, hctx, j) {

		if (j < i)

			blk_mq_unregister_hctx(hctx);

	}

	mutex_unlock(&q->tag_set->tag_list_lock);



	kobject_uevent(q->mq_kobj, KOBJ_REMOVE);

	kobject_del(q->mq_kobj);
@@ -256,9 +256,10 @@ void blk_mq_sysfs_unregister(struct gendisk *disk) 
	struct blk_mq_hw_ctx *hctx;

	unsigned long i;





	mutex_lock(&q->tag_set->tag_list_lock);

	queue_for_each_hw_ctx(q, hctx, i)

		blk_mq_unregister_hctx(hctx);

	mutex_unlock(&q->tag_set->tag_list_lock);



	kobject_uevent(q->mq_kobj, KOBJ_REMOVE);

	kobject_del(q->mq_kobj);