linux-kernel - Re: [PATCH 2/2] erofs: remove unnecessary kobject

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Date:   Thu, 6 Apr 2023 11:52:39 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Yangtao Li <frank.li@...o.com>, Gao Xiang <xiang@...nel.org>,
        Chao Yu <chao@...nel.org>, Yue Hu <huyue2@...lpad.com>,
        Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc:     linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] erofs: remove unnecessary kobject_del()

Hi Yangtao,

On 2023/4/4 22:21, Yangtao Li wrote:
> kobject_put() actually covers kobject removal automatically, which is
> single stage removal. So it is safe to kill kobject_del() directly.
> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>

Would you mind taking a look at
commit a942da24abc5 ("fs: erofs: add sanity check for kobject in erofs_unregister_sysfs")

, which could be "git-blame"ed (I'd suggest looking into these
blame first), and the related discussion was:

https://lore.kernel.org/r/CAD-N9QXNx=p3-QoWzk6pCznF32CZy8kM3vvo8mamfZZ9CpUKdw@mail.gmail.com
https://lore.kernel.org/r/20220315075152.63789-1-dzm91@hust.edu.cn

TL;DR: I guess it could be fixed as below if kobject_del() could
be killed safely:

	if (sbi->s_kobj.state_in_sysfs) {
		kobject_put(&sbi->s_kobj);
		wait_for_completion(&sbi->s_kobj_unregister);
	}

Thanks,
Gao Xiang


> ---
>   fs/erofs/sysfs.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index 435e515c0792..c3ba981b4472 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -240,11 +240,8 @@ void erofs_unregister_sysfs(struct super_block *sb)
>   {
>   	struct erofs_sb_info *sbi = EROFS_SB(sb);
>   
> -	if (sbi->s_kobj.state_in_sysfs) {
> -		kobject_del(&sbi->s_kobj);
> -		kobject_put(&sbi->s_kobj);
> -		wait_for_completion(&sbi->s_kobj_unregister);
> -	}
> +	kobject_put(&sbi->s_kobj);
> +	wait_for_completion(&sbi->s_kobj_unregister);
>   }
>   
>   int __init erofs_init_sysfs(void)