linux-ext4 - Re: [PATCH 2/2] ext4: update donor file's ctime/mtime

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Message-ID: <4AD52E2E.80404@sx.jp.nec.com>
Date:	Wed, 14 Oct 2009 10:49:34 +0900
From:	Kazuya Mio <k-mio@...jp.nec.com>
To:	Andreas Dilger <adilger@....com>
CC:	linux-ext4@...r.kernel.org, Theodore Tso <tytso@....edu>
Subject: Re: [PATCH 2/2] ext4: update donor file's ctime/mtime

2009/10/10 2:20, Andreas Dilger wrote::
> 
> On 8-Oct-09, at 02:04, Kazuya Mio wrote:
> 
>> EXT4_IOC_MOVE_EXT changes donor file data, but doesn't update 
>> ctime/mtime.
>> This patch fixes this problem.
> 
> I would argue that just migrating the file data shouldn't update the 
> ctime/mtime.
> Those are used to determine if the file has changed in some way, usually 
> for the
> purpose of backup.  Migrating the data does not change anything from the 
> user-space
> POV and shouldn't force a new backup of the file.

EXT4_IOC_MOVE_EXT always changes the original actual contents of donor file
if orig file and donor file aren't the same. It may be that some of
user-space implementations hide such a changing. For example, e4defrag
unlinks the donor file, and removes it by decreasing reference count after
calling EXT4_IOC_MOVE_EXT. But from the ioctl point of view,
EXT4_IOC_MOVE_EXT doesn't know whether donor file will be removed or not,
so I think we should update ctime/mtime.

Am I missing something?

Regards,
Kazuya Mio
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