linux-kernel - Re: [PATCH] debugfs show actual source in /proc/mounts

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Message-ID: <ad3a24af-5366-4c20-ad46-6f21d6754bbe@redhat.com>
Date: Fri, 30 Aug 2024 08:38:31 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: Marc Aurèle La France <tsi@...oix.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Christian Brauner <brauner@...nel.org>, David Howells <dhowells@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] debugfs show actual source in /proc/mounts

On 8/29/24 10:44 PM, Marc Aurèle La France wrote:
> After commit 0c07c273a5fe ("debugfs: continue to ignore unknown mount
> options"), debugfs displays "none" in /proc/mounts instead of the actual
> source.  Fix this by recognising its "source" mount option.
> 
> Signed-off-by: Marc Aurèle La France <tsi@...oix.net>
> Fixes: 0c07c273a5fe ("debugfs: continue to ignore unknown mount options")
> Cc: stable@...r.kernel.org # 6.10.x: 9f111059e725: fs_parse: add uid & gid option option parsing helpers
> Cc: stable@...r.kernel.org # 6.10.x: 49abee5991e1: debugfs: Convert to new uid/gid option parsing helpers
> 
> diff -NRapruz -X /etc/diff.excludes linux-6.11.0-rc2/fs/debugfs/inode.c devel-6.11.0-rc2/fs/debugfs/inode.c
> --- linux-6.11.0-rc5/fs/debugfs/inode.c
> +++ devel-6.11.0-rc5/fs/debugfs/inode.c
> @@ -89,12 +89,14 @@ enum {
>  	Opt_uid,
>  	Opt_gid,
>  	Opt_mode,
> +	Opt_source,
>  };
> 
>  static const struct fs_parameter_spec debugfs_param_specs[] = {
>  	fsparam_gid	("gid",		Opt_gid),
>  	fsparam_u32oct	("mode",	Opt_mode),
>  	fsparam_uid	("uid",		Opt_uid),
> +	fsparam_string	("source",	Opt_source),
>  	{}
>  };
> 
> @@ -126,6 +128,12 @@ static int debugfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
>  	case Opt_mode:
>  		opts->mode = result.uint_32 & S_IALLUGO;
>  		break;

Sorry for missing your earlier question, I was thinking that perhaps a
comment along the lines of this would be helpful:

	/*
	 * Because debugfs accepts all mount options and indicates
	 * success even for unknown options, we must process "source"
	 * ourselves here; the vfs won't do it for us.
	 */
> +	case Opt_source:
> +		if (fc->source)
> +			return invalfc(fc, "Multiple sources specified");
> +		fc->source = param->string;
> +		param->string = NULL;
> +		break;

but I suppose it's not a big deal unless others think it is.

Reviewed-by: Eric Sandeen <sandeen@...hat.com>

>  	/*
>  	 * We might like to report bad mount options here;
>  	 * but traditionally debugfs has ignored all mount options
>