On 8/21/19 2:15 AM, Ming Lei wrote:
@@ -966,7 +966,7 @@ int blk_register_queue(struct gendisk *disk)
return ret;
/* Prevent changes through sysfs until registration is completed. */
- mutex_lock(&q->sysfs_lock);
+ mutex_lock(&q->sysfs_dir_lock);
ret = kobject_add(&q->kobj, kobject_get(&dev->kobj), "%s", "queue");
if (ret < 0) {
@@ -987,26 +987,37 @@ int blk_register_queue(struct gendisk *disk)
blk_mq_debugfs_register(q);
}
- kobject_uevent(&q->kobj, KOBJ_ADD);
-
- wbt_enable_default(q);
-
- blk_throtl_register_queue(q);
-
+ /*
+ * The queue's kobject ADD uevent isn't sent out, also the
+ * flag of QUEUE_FLAG_REGISTERED isn't set yet, so elevator
+ * switch won't happen at all.
+ */
if (q->elevator) {
- ret = elv_register_queue(q);
+ ret = elv_register_queue(q, false);
if (ret) {
The above changes seems risky to me. In contrast with what the comment
suggests, user space code is not required to wait for KOBJ_ADD event to
start using sysfs attributes. I think user space code *can* write into
the request queue I/O scheduler sysfs attribute after the kobject_add()
call has finished and before kobject_uevent(&q->kobj, KOBJ_ADD) is called.
Bart.
