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From:   "Namjae Jeon" <namjae.jeon@samsung.com>
To:     "'Matthew Wilcox'" <willy@infradead.org>
Cc:     "'Namjae Jeon'" <namjae.jeon@samsung.com>,
        <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <torvalds@linux-foundation.org>,
        "'Eric Sandeen'" <sandeen@sandeen.net>
In-Reply-To: <004401d62fc9$4ba36620$e2ea3260$@samsung.com>
Subject: RE: [PATCH] exfat: add the dummy mount options to be backward
 compatible with staging/exfat
Date:   Fri, 22 May 2020 08:44:04 +0900
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References: <CGME20200521234105epcas1p14b910bcdc017938249a491a1b5207bb8@epcas1p1.samsung.com>
        <004401d62fc9$4ba36620$e2ea3260$@samsung.com>
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> On Thu, May 21, 2020 at 10:44:28AM -0500, Eric Sandeen wrote:
> > 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?
> 
> For NFS, 'intr' has been deprecated since December 2007 and has been printing a warning since June
> 2008.  How long until we delete it?
> 
> > >  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),
> 
>         __fsparam(NULL, "utf8",         Opt_utf8, fs_param_deprecated, NULL),
>         __fsparam(NULL, "debug",        Opt_debug, fs_param_deprecated, NULL),
>         __fsparam(fs_param_is_u32, "namecase", Opt_namecase,
>                                                 fs_param_deprecated, NULL),
>         __fsparam(fs_param_is_u32, "codepage", Opt_codepage,
>                                                 fs_param_deprecated, NULL),
> 
> > > @@ -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;
> 
> and then you don't need this hunk because the fs parser will print the deprecated message for you.
Fixed it on v3.
Thanks for your review!