linux-kernel - Re: [PATCH 2/3] erofs: convert to use kobject_is

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Date:   Thu, 6 Apr 2023 12:03:08 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yangtao Li <frank.li@...o.com>
Cc:     xiang@...nel.org, chao@...nel.org, huyue2@...lpad.com,
        jefflexu@...ux.alibaba.com, damien.lemoal@...nsource.wdc.com,
        naohiro.aota@....com, jth@...nel.org, rafael@...nel.org,
        linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/3] erofs: convert to use kobject_is_added()

On Thu, Apr 06, 2023 at 05:30:55PM +0800, Yangtao Li wrote:
> Use kobject_is_added() instead of directly accessing the internal
> variables of kobject. BTW kill kobject_del() directly, because
> kobject_put() actually covers kobject removal automatically.
> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
>  fs/erofs/sysfs.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index 435e515c0792..daac23e32026 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -240,8 +240,7 @@ 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 (kobject_is_added(&sbi->s_kobj)) {

I do not understand why this check is even needed, I do not think it
should be there at all as obviously the kobject was registered if it now
needs to not be registered.

Meta-comment, we need to come up with a "filesystem kobject type" to get
rid of lots of the boilerplate filesystem kobject logic as it's
duplicated in every filesystem in tiny different ways and lots of times
(like here), it's wrong.

kobjects were not designed to be "used raw" like this, ideally they
would be wrapped in a subsystem that makes them easier to be used (like
the driver model), but filesystems decided to use them and that usage
just grew over the years.  That's evolution for you...

thanks,

greg k-h