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Subject[PATCH v3 2/3] block: don't delete queue kobject before its children
Date
From: Eric Biggers <ebiggers@google.com>

kobjects aren't supposed to be deleted before their child kobjects are
deleted. Apparently this is usually benign; however, a WARN will be
triggered if one of the child kobjects has a named attribute group:

sysfs group 'modes' not found for kobject 'crypto'
WARNING: CPU: 0 PID: 1 at fs/sysfs/group.c:278 sysfs_remove_group+0x72/0x80
...
Call Trace:
sysfs_remove_groups+0x29/0x40 fs/sysfs/group.c:312
__kobject_del+0x20/0x80 lib/kobject.c:611
kobject_cleanup+0xa4/0x140 lib/kobject.c:696
kobject_release lib/kobject.c:736 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x53/0x70 lib/kobject.c:753
blk_crypto_sysfs_unregister+0x10/0x20 block/blk-crypto-sysfs.c:159
blk_unregister_queue+0xb0/0x110 block/blk-sysfs.c:962
del_gendisk+0x117/0x250 block/genhd.c:610

Fix this by moving the kobject_del() and the corresponding
kobject_uevent() to the correct place.

Fixes: 2c2086afc2b8 ("block: Protect less code with sysfs_lock in blk_{un,}register_queue()")
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
block/blk-sysfs.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 3152d244e9b36..c11242ef88558 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -952,15 +952,17 @@ void blk_unregister_queue(struct gendisk *disk)
*/
if (queue_is_mq(q))
blk_mq_unregister_dev(disk_to_dev(disk), q);
-
- kobject_uevent(&q->kobj, KOBJ_REMOVE);
- kobject_del(&q->kobj);
blk_trace_remove_sysfs(disk_to_dev(disk));

mutex_lock(&q->sysfs_lock);
elv_unregister_queue(q);
disk_unregister_independent_access_ranges(disk);
mutex_unlock(&q->sysfs_lock);
+
+ /* Now that all child objects were deleted, the queue can be deleted. */
+ kobject_uevent(&q->kobj, KOBJ_REMOVE);
+ kobject_del(&q->kobj);
+
mutex_unlock(&q->sysfs_dir_lock);

kobject_put(&disk_to_dev(disk)->kobj);
--
2.34.1
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