From: Jaegeuk Kim <jaegeuk.kim@samsung.com>
To: "'Arnd Bergmann'" <arnd@arndb.de>, "'Jaegeuk Kim'" <jaegeuk.kim@gmail.com>
Cc: "'Dave Chinner'" <david@fromorbit.com>,
        "'Vyacheslav Dubeyko'" <slava@dubeyko.com>, viro@zeniv.linux.org.uk,
        "'Theodore Ts'o'" <tytso@mit.edu>, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org, chur.lee@samsung.com,
        cm224.lee@samsung.com, jooyoung.hwang@samsung.com
References: <001201cda2f1$633db960$29b92c20$%kim@samsung.com>
 <201210161138.35388.arnd@arndb.de> <1350419915.1958.39.camel@kjgkr>
 <201210171225.01511.arnd@arndb.de>
In-reply-to: <201210171225.01511.arnd@arndb.de>
Subject: RE: [PATCH 11/16] f2fs: add inode operations for special inodes
Date: Thu, 18 Oct 2012 14:37:49 +0900
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> On Tuesday 16 October 2012, Jaegeuk Kim wrote:
> > >
> > > > > An xattr on the root inode that holds a list like this is something
> > > > > that could be set at mkfs time, but then also updated easily by new
> > > > > software packages that are installed...
> > >
> > > Yes, good idea.
> >
> > Likewise many file systems, f2fs also supports xattr as a configurable
> > Kconfig option.
> > If user disables the xattr feature, how can we do this?
> 
> I can see three options here:
> 
> * make the extension list feature dependent on xattr, and treat all files
>   the same if it's disabled.
> 
> * put the list into the superblock instead.
> 
> * fall back on a hardcoded list of extensions when the extended attribute
>   is not present or the feature is disabled.
> 

IMHO, we don't need to disable the extension list among the cases.
So, as I described before, I propose the following options.

* By default, mkfs stores an extension list in superblock, and f2fs simply
   uses it.
* If users try to handle cold files by themselves, they can give a hint
  via the xattr interface.
* Whenever they want not to use the default extension list, they can
  easily disable it by a mount option.

> 	Arnd

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