Commit b410aff2 authored by Tahsin Erdogan's avatar Tahsin Erdogan Committed by Jens Axboe

block: do not allow updates through sysfs until registration completes

When a new disk shows up, sysfs queue directory is created before elevator
is registered. This allows a user to attempt a scheduler switch even though
the initial registration hasn't completed yet.

In one scenario, blk_register_queue() calls elv_register_queue() and
right before cfq_registered_queue() is called, another process executes
elevator_switch() and replaces q->elevator with deadline scheduler. When
cfq_registered_queue() executes it interprets e->elevator_data as struct
cfq_data even though it is actually struct deadline_data.

Grab q->sysfs_lock in blk_register_queue() to synchronize with sysfs
Signed-off-by: default avatarTahsin Erdogan <>
Signed-off-by: default avatarJens Axboe <>
parent 3d492c2e
......@@ -902,17 +902,20 @@ int blk_register_queue(struct gendisk *disk)
if (ret)
return ret;
if (q->mq_ops)
blk_mq_register_dev(dev, q);
/* Prevent changes through sysfs until registration is completed. */
ret = kobject_add(&q->kobj, kobject_get(&dev->kobj), "%s", "queue");
if (ret < 0) {
return ret;
goto unlock;
kobject_uevent(&q->kobj, KOBJ_ADD);
if (q->mq_ops)
blk_mq_register_dev(dev, q);
if (q->request_fn || (q->mq_ops && q->elevator)) {
......@@ -922,11 +925,13 @@ int blk_register_queue(struct gendisk *disk)
return ret;
goto unlock;
return 0;
ret = 0;
return ret;
void blk_unregister_queue(struct gendisk *disk)
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