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Date: Mon, 4 Apr 2022 14:02:38 +0000
From: Al Viro <viro@zeniv.linux.org.uk>
To: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Amir Goldstein <amir73il@gmail.com>, kernel@collabora.com,
	Khazhismel Kumykov <khazhy@google.com>,
	Linux MM <linux-mm@kvack.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH RESEND 2/3] shmem: Introduce /sys/fs/tmpfs support
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 <20220404134137.26284-3-krisman@collabora.com>
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On Mon, Apr 04, 2022 at 09:41:36AM -0400, Gabriel Krisman Bertazi wrote:
> In order to expose tmpfs statistics on sysfs, add the boilerplate code
> to create the /sys/fs/tmpfs structure.  As suggested on a previous
> review, this uses the minor as the volume directory in /sys/fs/.
> 
> This takes care of not exposing SB_NOUSER mounts.  I don't think we have
> a usecase for showing them and, since they don't appear elsewhere, they
> might be confusing to users.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

> +static void shmem_unregister_sysfs(struct super_block *sb)
> +{
> +	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
> +
> +	kobject_del(&sbinfo->s_kobj);
> +	kobject_put(&sbinfo->s_kobj);
> +	wait_for_completion(&sbinfo->s_kobj_unregister);
> +}

If you embed kobject into something, you basically commit to
having the lifetime rules maintained by that kobject...