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Commit 2c2086af authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
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block: Protect less code with sysfs_lock in blk_{un,}register_queue() 



The __blk_mq_register_dev(), blk_mq_unregister_dev(),
elv_register_queue() and elv_unregister_queue() calls need to be
protected with sysfs_lock but other code in these functions not.
Hence protect only this code with sysfs_lock. This patch fixes a
locking inversion issue in blk_unregister_queue() and also in an
error path of blk_register_queue(): it is not allowed to hold
sysfs_lock around the kobject_del(&q->kobj) call.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 14a23498

block/blk-sysfs.c

+28 −9
Original line number Diff line number Diff line
@@ -853,6 +853,10 @@ struct kobj_type blk_queue_ktype = { 
	.release	= blk_release_queue,

};



/**

 * blk_register_queue - register a block layer queue with sysfs

 * @disk: Disk of which the request queue should be registered with sysfs.

 */

int blk_register_queue(struct gendisk *disk)

{

	int ret;
@@ -909,11 +913,12 @@ int blk_register_queue(struct gendisk *disk) 
	if (q->request_fn || (q->mq_ops && q->elevator)) {

		ret = elv_register_queue(q);

		if (ret) {

			mutex_unlock(&q->sysfs_lock);

			kobject_uevent(&q->kobj, KOBJ_REMOVE);

			kobject_del(&q->kobj);

			blk_trace_remove_sysfs(dev);

			kobject_put(&dev->kobj);

			goto unlock;

			return ret;

		}

	}

	ret = 0;
@@ -923,6 +928,13 @@ int blk_register_queue(struct gendisk *disk) 
}

EXPORT_SYMBOL_GPL(blk_register_queue);



/**

 * blk_unregister_queue - counterpart of blk_register_queue()

 * @disk: Disk of which the request queue should be unregistered from sysfs.

 *

 * Note: the caller is responsible for guaranteeing that this function is called

 * after blk_register_queue() has finished.

 */

void blk_unregister_queue(struct gendisk *disk)

{

	struct request_queue *q = disk->queue;
@@ -935,8 +947,9 @@ void blk_unregister_queue(struct gendisk *disk) 
		return;



	/*

	 * Protect against the 'queue' kobj being accessed

	 * while/after it is removed.

	 * Since sysfs_remove_dir() prevents adding new directory entries

	 * before removal of existing entries starts, protect against

	 * concurrent elv_iosched_store() calls.

	 */

	mutex_lock(&q->sysfs_lock);
@@ -944,18 +957,24 @@ void blk_unregister_queue(struct gendisk *disk) 
	queue_flag_clear(QUEUE_FLAG_REGISTERED, q);

	spin_unlock_irq(q->queue_lock);



	wbt_exit(q);



	/*

	 * Remove the sysfs attributes before unregistering the queue data

	 * structures that can be modified through sysfs.

	 */

	if (q->mq_ops)

		blk_mq_unregister_dev(disk_to_dev(disk), q);



	if (q->request_fn || (q->mq_ops && q->elevator))

		elv_unregister_queue(q);

	mutex_unlock(&q->sysfs_lock);



	kobject_uevent(&q->kobj, KOBJ_REMOVE);

	kobject_del(&q->kobj);

	blk_trace_remove_sysfs(disk_to_dev(disk));

	kobject_put(&disk_to_dev(disk)->kobj);



	wbt_exit(q);



	mutex_lock(&q->sysfs_lock);

	if (q->request_fn || (q->mq_ops && q->elevator))

		elv_unregister_queue(q);

	mutex_unlock(&q->sysfs_lock);



	kobject_put(&disk_to_dev(disk)->kobj);

}