linux-kernel - Re: [PATCH v2] exfat: add the dummy mount options to be backward compatible with staging/exfat

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Date:   Thu, 21 May 2020 10:44:28 -0500
From:   Eric Sandeen <sandeen@...deen.net>
To:     Namjae Jeon <linkinjeon@...nel.org>, linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH v2] exfat: add the dummy mount options to be backward
 compatible with staging/exfat

On 5/21/20 9:05 AM, Namjae Jeon wrote:
> As Ubuntu and Fedora release new version used kernel version equal to or
> higher than v5.4, They started to support kernel exfat filesystem.
> 
> Linus Torvalds reported mount error with new version of exfat on Fedora.
> 
> 	exfat: Unknown parameter 'namecase'
> 
> This is because there is a difference in mount option between old
> staging/exfat and new exfat.
> And utf8, debug, and codepage options as well as namecase have been
> removed from new exfat.
> 
> This patch add the dummy mount options as deprecated option to be backward
> compatible with old one.

Wow, it seems wild that we'd need to maintain compatibility with options
which only ever existed in a different codebase in a staging driver
(what's the point of staging if every interface that makes it that far has
to be maintained in perpetuity?)

Often, when things are deprecated, they are eventually removed.  Perhaps a
future removal date stated in this commit, or in Documentation/..../exfat.txt
would be good as a reminder to eventually remove this?

-Eric

> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Namjae Jeon <linkinjeon@...nel.org>
> ---
> v2:
>  - fix checkpatch.pl warning(Missing Signed-off-by).
> 
>  fs/exfat/super.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/fs/exfat/super.c b/fs/exfat/super.c
> index 0565d5539d57..26b0db5b20de 100644
> --- a/fs/exfat/super.c
> +++ b/fs/exfat/super.c
> @@ -203,6 +203,12 @@ enum {
>  	Opt_errors,
>  	Opt_discard,
>  	Opt_time_offset,
> +
> +	/* Deprecated options */
> +	Opt_utf8,
> +	Opt_debug,
> +	Opt_namecase,
> +	Opt_codepage,
>  };
>  
>  static const struct constant_table exfat_param_enums[] = {
> @@ -223,6 +229,10 @@ static const struct fs_parameter_spec exfat_parameters[] = {
>  	fsparam_enum("errors",			Opt_errors, exfat_param_enums),
>  	fsparam_flag("discard",			Opt_discard),
>  	fsparam_s32("time_offset",		Opt_time_offset),
> +	fsparam_flag("utf8",			Opt_utf8),
> +	fsparam_flag("debug",			Opt_debug),
> +	fsparam_u32("namecase",			Opt_namecase),
> +	fsparam_u32("codepage",			Opt_codepage),
>  	{}
>  };
>  
> @@ -278,6 +288,18 @@ static int exfat_parse_param(struct fs_context *fc, struct fs_parameter *param)
>  			return -EINVAL;
>  		opts->time_offset = result.int_32;
>  		break;
> +	case Opt_utf8:
> +		pr_warn("exFAT-fs: 'utf8' mount option is deprecated and has no effect\n");
> +		break;
> +	case Opt_debug:
> +		pr_warn("exFAT-fs: 'debug' mount option is deprecated and has no effect\n");
> +		break;
> +	case Opt_namecase:
> +		pr_warn("exFAT-fs: 'namecase' mount option is deprecated and has no effect\n");
> +		break;
> +	case Opt_codepage:
> +		pr_warn("exFAT-fs: 'codepage' mount option is deprecated and has no effect\n");
> +		break;
>  	default:
>  		return -EINVAL;
>  	}
>