Re: [PATCH] blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister_hctx

[Yu Kuai]

在 2025/08/26 16:48, linan666@xxxxxxxxxxxxxxx 写道:
> From: Li Nan <linan122@xxxxxxxxxx>
>
> In __blk_mq_update_nr_hw_queues() the return value of
> blk_mq_sysfs_register_hctxs() is not checked. If sysfs creation for hctx
> fails, later changing the number of hw_queues or removing disk will
> trigger the following warning:
>
>    kernfs: can not remove 'nr_tags', no directory
>    WARNING: CPU: 2 PID: 637 at fs/kernfs/dir.c:1707 kernfs_remove_by_name_ns+0x13f/0x160
>    Call Trace:
>     remove_files.isra.1+0x38/0xb0
>     sysfs_remove_group+0x4d/0x100
>     sysfs_remove_groups+0x31/0x60
>     __kobject_del+0x23/0xf0
>     kobject_del+0x17/0x40
>     blk_mq_unregister_hctx+0x5d/0x80
>     blk_mq_sysfs_unregister_hctxs+0x94/0xd0
>     blk_mq_update_nr_hw_queues+0x124/0x760
>     nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]
>     nullb_device_submit_queues_store+0x92/0x120 [null_blk]
>
> kobjct_del() was called unconditionally even if sysfs creation failed.
> Fix it by checkig the kobject creation statusbefore deleting it.
>
> Fixes: 477e19dedc9d ("blk-mq: adjust debugfs and sysfs register when updating nr_hw_queues")
> Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> ---
>   block/blk-mq-sysfs.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
LGTM
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>