linux-kernel - Re: [PATCH v2] vfs: Don't exchange "short" filenames unconditionally.

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Message-ID: <20140925044601.GL7996@ZenIV.linux.org.uk>
Date:	Thu, 25 Sep 2014 05:46:01 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Mikhail Efremov <sem@...linux.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH v2] vfs: Don't exchange "short" filenames unconditionally.

On Wed, Sep 24, 2014 at 09:18:13PM +0100, Al Viro wrote:
> On Wed, Sep 24, 2014 at 12:20:38PM -0700, Linus Torvalds wrote:
> > On Wed, Sep 24, 2014 at 11:55 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
> > >
> > > Yecchhhh...  Applied, but it's very ugly.  Oh, well - regression is
> > > regression, and I don't see a cleaner fix at the moment.  If I don't
> > > manage to come up with anything prettier, to Linus it goes in tonight
> > > pull request ;-/
> > 
> > Please don't. That thing is too ugly to exist. It also looks
> > completely and utterly buggy. There's no way I'm taking it. If
> > switch-names is suddenly conditional, what the f*ck happens to the
> > name hash which is unconditionally done with a swap() right
> > afterwards.
> 
> The sucker's unhashed after that...  And yes, I agree that it's fucking
> ugly.  Still looking for saner ways to do that...

I really wonder if it's possible to get d_rehash() hitting the victim of
(non-exchange) __d_move().  _Then_ this patch (as well as the historical
behaviour it restores, all way back to 2.5, if not 2.3) would, indeed,
be buggy.

I'd probably better sleep on that and finish YACrawlingTFS tomorrow morning
- it's nearly 1am here and I've got only 5 hours of sleep left until it's time
to get the kids up for school ;-/
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