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block: Protect less code with sysfs_lock in blk_{un,}register_queue()

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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2018-01-17 11:48:10 -08:00 committed by Jens Axboe
parent 14a23498ba
commit 2c2086afc2
1 changed files with 28 additions and 9 deletions
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37
block/blk-sysfs.c
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@ -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);
}