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block: fix kobject double initialization in add_disk

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Device-mapper can call add_disk() multiple times for the same gendisk
due to its two-phase creation process (dm create + dm load). This leads
to kobject double initialization errors when the underlying iSCSI devices
become temporarily unavailable and then reappear.

However, if the first add_disk() call fails and is retried, the queue_kobj
gets initialized twice, causing:

kobject: kobject (ffff88810c27bb90): tried to init an initialized object,
something is seriously wrong.
 Call Trace:
  <TASK>
  dump_stack_lvl+0x5b/0x80
  kobject_init.cold+0x43/0x51
  blk_register_queue+0x46/0x280
  add_disk_fwnode+0xb5/0x280
  dm_setup_md_queue+0x194/0x1c0
  table_load+0x297/0x2d0
  ctl_ioctl+0x2a2/0x480
  dm_ctl_ioctl+0xe/0x20
  __x64_sys_ioctl+0xc7/0x110
  do_syscall_64+0x72/0x390
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fix this by separating kobject initialization from sysfs registration:
 - Initialize queue_kobj early during gendisk allocation
 - add_disk() only adds the already-initialized kobject to sysfs
 - del_gendisk() removes from sysfs but doesn't destroy the kobject
 - Final cleanup happens when the disk is released

Fixes: 2bd85221a6 ("block: untangle request_queue refcounting from sysfs")
Reported-by: Li Lingfeng <lilingfeng3@huawei.com>
Closes: https://lore.kernel.org/all/83591d0b-2467-433c-bce0-5581298eb161@huawei.com/
Signed-off-by: Zheng Qixing <zhengqixing@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250808053609.3237836-1-zhengqixing@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Zheng Qixing 2025-08-08 13:36:09 +08:00 committed by Jens Axboe
parent 196447c712
commit 343dc5423b
3 changed files with 8 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
block/blk-sysfs.c
View File

@ -847,7 +847,7 @@ static void blk_queue_release(struct kobject *kobj)
/* nothing to do here, all data is associated with the parent gendisk */
}
static const struct kobj_type blk_queue_ktype = {
const struct kobj_type blk_queue_ktype = {
.default_groups = blk_queue_attr_groups,
.sysfs_ops = &queue_sysfs_ops,
.release = blk_queue_release,
@ -875,15 +875,14 @@ int blk_register_queue(struct gendisk *disk)
struct request_queue *q = disk->queue;
int ret;
kobject_init(&disk->queue_kobj, &blk_queue_ktype);
ret = kobject_add(&disk->queue_kobj, &disk_to_dev(disk)->kobj, "queue");
if (ret < 0)
goto out_put_queue_kobj;
return ret;
if (queue_is_mq(q)) {
ret = blk_mq_sysfs_register(disk);
if (ret)
goto out_put_queue_kobj;
goto out_del_queue_kobj;
}
mutex_lock(&q->sysfs_lock);
@ -934,8 +933,8 @@ out_debugfs_remove:
mutex_unlock(&q->sysfs_lock);
if (queue_is_mq(q))
blk_mq_sysfs_unregister(disk);
out_put_queue_kobj:
kobject_put(&disk->queue_kobj);
out_del_queue_kobj:
kobject_del(&disk->queue_kobj);
return ret;
}
@ -986,5 +985,4 @@ void blk_unregister_queue(struct gendisk *disk)
elevator_set_none(q);
blk_debugfs_remove(disk);
kobject_put(&disk->queue_kobj);
}

1
block/blk.h
View File

@ -29,6 +29,7 @@ struct elevator_tags;
/* Max future timer expiry for timeouts */
#define BLK_MAX_TIMEOUT (5 * HZ)
extern const struct kobj_type blk_queue_ktype;
extern struct dentry *blk_debugfs_root;
struct blk_flush_queue {

2
block/genhd.c
View File

@ -1303,6 +1303,7 @@ static void disk_release(struct device *dev)
disk_free_zone_resources(disk);
xa_destroy(&disk->part_tbl);
kobject_put(&disk->queue_kobj);
disk->queue->disk = NULL;
blk_put_queue(disk->queue);
@ -1486,6 +1487,7 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
INIT_LIST_HEAD(&disk->slave_bdevs);
#endif
mutex_init(&disk->rqos_state_mutex);
kobject_init(&disk->queue_kobj, &blk_queue_ktype);
return disk;
out_erase_part0: