linux-ext4 - Re: [PATCH] ext2: Do not update mtime of a move directory when parent has not changed

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Message-ID: <20090409191515.GB3886@duck.suse.cz>
Date:	Thu, 9 Apr 2009 21:15:15 +0200
From:	Jan Kara <jack@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-ext4@...r.kernel.org, ronny.pretzsch@....de, hare@...e.de
Subject: Re: [PATCH] ext2: Do not update mtime of a move directory when
	parent has not changed

On Thu 09-04-09 11:51:32, Andrew Morton wrote:
> On Thu,  9 Apr 2009 20:41:32 +0200
> Jan Kara <jack@...e.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@....de, initial fix by J__rn Engel <joern@...fs.org>.
> > 
> > CC: ronny.pretzsch@....de
> > CC: hare@...e.de
> > Acked-by: J__rn Engel <joern@...fs.org>
> > Signed-off-by: Jan Kara <jack@...e.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.
  Yes, I think so as well. Looking more into what other filesystems do, it
seems that FAT, UDF, reiserfs, ext3, ext4 actually never update mtime of
the moved directory, even if the parent has changed. So maybe it would make
more sence to change ext2 in this way as well. What do you think?

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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