linux-kernel - Re: [PATCH] erofs: don't access kobject object members directly

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Date:   Wed, 12 Apr 2023 11:24:22 +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>,
        Huang Jianan <jnhuang@...ux.alibaba.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dongliang Mu <mudongliangabcd@...il.com>
Cc:     linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] erofs: don't access kobject object members directly

(+ Greg, Huang Jianan, Dongliang Mu)

On 2023/4/12 11:11, Yangtao Li wrote:
> It is better not to directly access the internal members of the
> kobject object, especially kobject_init_and_add() may failure.
> BTW remove unnecessary kobject_del(), kobject_put() actually covers
> kobject removal automatically, which is single stage removal.

Please at least Cc the proper people --- and write
the previous background to the commit message *again*.

I'd like to know the preferred way to do this since
the previous discussion is unfinished.

Also if you grep `state_in_sysfs`, actually there are
some similar in-tree usage, also device_is_registered() is
implemented like this:

static inline int device_is_registered(struct device *dev)
{
	return dev->kobj.state_in_sysfs;
}

Again, I'm not against this patch (I even prefer this one),
but you should Cc the proper people and finish the previous
topic first.

Thanks,
Gao Xiang

> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
>   fs/erofs/internal.h | 1 +
>   fs/erofs/sysfs.c    | 4 ++--
>   2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index f675050af2bb..f364b1e9b35b 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -177,6 +177,7 @@ struct erofs_sb_info {
>   	/* sysfs support */
>   	struct kobject s_kobj;		/* /sys/fs/erofs/<devname> */
>   	struct completion s_kobj_unregister;
> +	bool sysfs_registered;
>   
>   	/* fscache support */
>   	struct fscache_volume *volume;
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index 435e515c0792..c38018d3c442 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -228,6 +228,7 @@ int erofs_register_sysfs(struct super_block *sb)
>   	kfree(str);
>   	if (err)
>   		goto put_sb_kobj;
> +	sbi->sysfs_registered = true;
>   	return 0;
>   
>   put_sb_kobj:
> @@ -240,8 +241,7 @@ 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);
> +	if (sbi->sysfs_registered) {
>   		kobject_put(&sbi->s_kobj);
>   		wait_for_completion(&sbi->s_kobj_unregister);
>   	}