linux-kernel - Re: Finding hardlinks

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Message-ID: <20070108112713.GA25857@elf.ucw.cz>
Date:	Mon, 8 Jan 2007 12:27:14 +0100
From:	Pavel Machek <pavel@....cz>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	mikulas@...ax.karlin.mff.cuni.cz, matthew@....cx,
	bhalevy@...asas.com, arjan@...radead.org, jaharkes@...cmu.edu,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	nfsv4@...f.org
Subject: Re: Finding hardlinks

On Fri 2007-01-05 16:15:41, Miklos Szeredi wrote:
> > > And does it matter? If you rename a file, tar might skip it no matter of 
> > > hardlink detection (if readdir races with rename, you can read none of the 
> > > names of file, one or both --- all these are possible).
> > > 
> > > If you have "dir1/a" hardlinked to "dir1/b" and while tar runs you delete 
> > > both "a" and "b" and create totally new files "dir2/c" linked to "dir2/d", 
> > > tar might hardlink both "c" and "d" to "a" and "b".
> > > 
> > > No one guarantees you sane result of tar or cp -a while changing the tree. 
> > > I don't see how is_samefile() could make it worse.
> > 
> > There are several cases where changing the tree doesn't affect the
> > correctness of the tar or cp -a result.  In some of these cases using
> > samefile() instead of st_ino _will_ result in a corrupted result.
> 
> Also note, that using st_ino in combination with samefile() doesn't
> make the result much better, it eliminates false positives, but cannot
> fix false negatives.

I'd argue false negatives are not as severe.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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