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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, .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 blk_register_queue(struct gendisk *disk)
{ {
int ret; int ret;
@ -909,11 +913,12 @@ int blk_register_queue(struct gendisk *disk)
if (q->request_fn || (q->mq_ops && q->elevator)) { if (q->request_fn || (q->mq_ops && q->elevator)) {
ret = elv_register_queue(q); ret = elv_register_queue(q);
if (ret) { if (ret) {
mutex_unlock(&q->sysfs_lock);
kobject_uevent(&q->kobj, KOBJ_REMOVE); kobject_uevent(&q->kobj, KOBJ_REMOVE);
kobject_del(&q->kobj); kobject_del(&q->kobj);
blk_trace_remove_sysfs(dev); blk_trace_remove_sysfs(dev);
kobject_put(&dev->kobj); kobject_put(&dev->kobj);
goto unlock; return ret;
} }
} }
ret = 0; ret = 0;
@ -923,6 +928,13 @@ unlock:
} }
EXPORT_SYMBOL_GPL(blk_register_queue); 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) void blk_unregister_queue(struct gendisk *disk)
{ {
struct request_queue *q = disk->queue; struct request_queue *q = disk->queue;
@ -935,8 +947,9 @@ void blk_unregister_queue(struct gendisk *disk)
return; return;
/* /*
* Protect against the 'queue' kobj being accessed * Since sysfs_remove_dir() prevents adding new directory entries
* while/after it is removed. * before removal of existing entries starts, protect against
* concurrent elv_iosched_store() calls.
*/ */
mutex_lock(&q->sysfs_lock); mutex_lock(&q->sysfs_lock);
@ -944,18 +957,24 @@ void blk_unregister_queue(struct gendisk *disk)
queue_flag_clear(QUEUE_FLAG_REGISTERED, q); queue_flag_clear(QUEUE_FLAG_REGISTERED, q);
spin_unlock_irq(q->queue_lock); 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) if (q->mq_ops)
blk_mq_unregister_dev(disk_to_dev(disk), q); blk_mq_unregister_dev(disk_to_dev(disk), q);
mutex_unlock(&q->sysfs_lock);
if (q->request_fn || (q->mq_ops && q->elevator))
elv_unregister_queue(q);
kobject_uevent(&q->kobj, KOBJ_REMOVE); kobject_uevent(&q->kobj, KOBJ_REMOVE);
kobject_del(&q->kobj); kobject_del(&q->kobj);
blk_trace_remove_sysfs(disk_to_dev(disk)); 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); mutex_unlock(&q->sysfs_lock);
kobject_put(&disk_to_dev(disk)->kobj);
} }