From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] ext2: Do not update mtime of a move directory when
 parent has not changed
Date: Thu, 9 Apr 2009 11:51:32 -0700
Message-ID: <20090409115132.9f7ccaf0.akpm@linux-foundation.org>
References: <1239302492-10455-1-git-send-email-jack@suse.cz>
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Cc: linux-ext4@vger.kernel.org, jack@suse.cz, ronny.pretzsch@dfs.de,
	hare@suse.de
To: Jan Kara <jack@suse.cz>
In-Reply-To: <1239302492-10455-1-git-send-email-jack@suse.cz>
Sender: linux-ext4-owner@vger.kernel.org

On Thu,  9 Apr 2009 20:41:32 +0200
Jan Kara <jack@suse.cz> wrote:

> If the parent of the moved directory has not changed, there's no real
> reason to change mtime. Specs doesn't seem to say anything about this
> particular case and e.g. ext3 does not change mtime in this case.
> So we become a tiny bit more consistent.
> 
> Spotted by ronny.pretzsch@dfs.de, initial fix by J__rn Engel <joern@logfs.org>.
> 
> CC: ronny.pretzsch@dfs.de
> CC: hare@suse.de
> Acked-by: J__rn Engel <joern@logfs.org>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/ext2/namei.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
> index 90ea179..556f258 100644
> --- a/fs/ext2/namei.c
> +++ b/fs/ext2/namei.c
> @@ -352,7 +352,10 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
>  	inode_dec_link_count(old_inode);
>  
>  	if (dir_de) {
> -		ext2_set_link(old_inode, dir_de, dir_page, new_dir);
> +		/* Set link only if parent has changed and thus avoid setting
> +		 * of mtime of the moved directory on a pure rename. */
> +		if (old_dir != new_dir)
> +			ext2_set_link(old_inode, dir_de, dir_page, new_dir);
>  		inode_dec_link_count(old_dir);
>  	}
>  	return 0;

hm, what do other filesystems do?  We risk breaking things in either case.
Probably changing ext2 is safer than changing ext3/4, given that ext2 is
used less.