linux-kernel - Re: [PATCH v3 01/10] kobject: introduce kobject_del_and

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Date:   Thu, 23 Mar 2023 08:31:30 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Yangtao Li <frank.li@...o.com>, clm@...com, josef@...icpanda.com,
        dsterba@...e.com, xiang@...nel.org, chao@...nel.org,
        huyue2@...lpad.com, jefflexu@...ux.alibaba.com, jaegeuk@...nel.org,
        trond.myklebust@...merspace.com, anna@...nel.org,
        konishi.ryusuke@...il.com, mark@...heh.com, jlbec@...lplan.org,
        joseph.qi@...ux.alibaba.com, richard@....at, djwong@...nel.org,
        naohiro.aota@....com, jth@...nel.org, gregkh@...uxfoundation.org,
        rafael@...nel.org
Cc:     linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-erofs@...ts.ozlabs.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-nfs@...r.kernel.org,
        linux-nilfs@...r.kernel.org, ocfs2-devel@....oracle.com,
        linux-mtd@...ts.infradead.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 01/10] kobject: introduce kobject_del_and_put()

On 3/23/23 01:58, Yangtao Li wrote:
> There are plenty of using kobject_del() and kobject_put() together
> in the kernel tree. This patch wraps these two calls in a single helper.
> 
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> ---
> v3:
> -convert to inline helper
> v2:
> -add kobject_del_and_put() users
>  include/linux/kobject.h | 13 +++++++++++++
>  lib/kobject.c           |  3 +--
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/kobject.h b/include/linux/kobject.h
> index bdab370a24f4..e21b7c22e355 100644
> --- a/include/linux/kobject.h
> +++ b/include/linux/kobject.h
> @@ -112,6 +112,19 @@ extern struct kobject * __must_check kobject_get_unless_zero(
>  						struct kobject *kobj);
>  extern void kobject_put(struct kobject *kobj);
>  
> +/**
> + * kobject_del_and_put() - Delete kobject.
> + * @kobj: object.
> + *
> + * Unlink kobject from hierarchy and decrement the refcount.

Unlink kobject from hierarchy and decrement its refcount.

> + * If refcount is 0, call kobject_cleanup().

That is done by kobject_put() and not explicitly done directly in this helper.
So I would not mention this to avoid confusion as you otherwise have a
description that does not match the code we can see here.

With that fixed, this looks OK to me, so feel free to add:

Reviewed-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>

> + */
> +static inline void kobject_del_and_put(struct kobject *kobj)
> +{
> +	kobject_del(kobj);
> +	kobject_put(kobj);
> +}
> +
>  extern const void *kobject_namespace(const struct kobject *kobj);
>  extern void kobject_get_ownership(const struct kobject *kobj,
>  				  kuid_t *uid, kgid_t *gid);
> diff --git a/lib/kobject.c b/lib/kobject.c
> index f79a434e1231..e6c5a3ff1c53 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -876,8 +876,7 @@ void kset_unregister(struct kset *k)
>  {
>  	if (!k)
>  		return;
> -	kobject_del(&k->kobj);
> -	kobject_put(&k->kobj);
> +	kobject_del_and_put(&k->kobj);

Nit: You could simplify this one to be:

	if (k)
		kobject_del_and_put(&k->kobj);

and drop the return line.

>  }
>  EXPORT_SYMBOL(kset_unregister);
>  

-- 
Damien Le Moal
Western Digital Research