linux-kernel - Re: MS_SILENT vs. vfat and hfs

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Message-ID: <20110302144303.GC14636@nb.net.home>
Date:	Wed, 2 Mar 2011 15:43:03 +0100
From:	Karel Zak <kzak@...hat.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	linux-kernel@...r.kernel.org, t.artem@...lcity.com,
	Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: MS_SILENT vs. vfat and hfs

On Wed, Mar 02, 2011 at 11:14:28PM +0900, OGAWA Hirofumi wrote:
> Karel Zak <kzak@...hat.com> writes:
> 
> >  The mount(8) command uses "quiet" mount option as a synonym to the
> >  MS_SILENT mount flag (since util-linux 2.7, Aug 1997).
> >
> >  It means than on systems where is properly defined the MS_SILENT
> >  mount flags in headers is the "quiet" mount option always translated
> >  to the MS_SILENT mount flags and "quiet" string is never send to FS
> >  drivers.
> >
> >    $ strace -e mount mount -o quiet /dev/sdb1 /mnt/test
> >    mount("/dev/sdb1", "/mnt/test", "vfat", MS_MGC_VAL|MS_SILENT, NULL) = 0
> >                                                       ^^^^^^^^^
> >
> >  Unfortunately, 
> >  
> >    $ grep -r \"quiet\" *
> >
> >    fat/inode.c:    {Opt_quiet, "quiet"},
> >    hfs/super.c:    { opt_quiet, "quiet" },
> >
> >  vfat and hfs drivers use "quiet" as a mount option. That's bug.
> >
> >  There should not be a collision between mount(8) mount options and
> >  filesystem specific mount options.
> >
> >  My suggestion is to fix the fat and hfs code to use something other
> >  than "quiet" (shutup, noisless, ...). I think you don't have to care
> >  about backward compatibility, because it's probably broken for years.
> 
> No. Actually the _new_ option is MS_SILENT. In history, there was no
> MS_SILENT (it was called MS_VERBOSE) in kernel, then _added_ newly, and
> never be enabled MS_SILENT in mount command until that.

 I know, but I don't care which option is newer. I'd like to found a
 solution with minimal impact to users.

> So, my suggestion is use "silent" (or something) as MS_SILENT for
> backward compatibility. Because the "quiet" is already hardcoded by some
> userland apps for vfat.

 Then all people who use "quiet" in their fstab will see problems...

    Karel

-- 
 Karel Zak  <kzak@...hat.com>
 http://karelzak.blogspot.com
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