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

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Date:	Thu, 03 Mar 2011 00:13:54 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Karel Zak <kzak@...hat.com>
Cc:	linux-kernel@...r.kernel.org, t.artem@...lcity.com,
	Roman Zippel <zippel@...ux-m68k.org>
Subject: Re: MS_SILENT vs. vfat and hfs

Karel Zak <kzak@...hat.com> writes:

> 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.

Sounds good.

>> 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...

I don't know how to know the minimal impact though. I'll bet to change
MS_SILENT, because at least the mount command in debian/testing doesn't
provide "quiet" as MS_SILENT.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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