linux-kernel - Re: Q: NFSD readdir in linux-2.6.28

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Date:	Fri, 17 Apr 2009 23:55:46 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	hooanon05@...oo.co.jp, hch@...radead.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: Q: NFSD readdir in linux-2.6.28

On Fri, 2009-04-17 at 23:53 +0100, Al Viro wrote:
> On Fri, Apr 17, 2009 at 11:43:50PM +0100, Al Viro wrote:
> > On Fri, Apr 17, 2009 at 11:17:00PM +0100, David Woodhouse wrote:
> > > It sounds like the better answer is to just make sure i_mutex is held
> > > when nfsd_buffered_readdir() calls back into the provided filldir
> > > function (we could do it in the various filldir functions themselves,
> > > _if_ they call lookup_one_len(), but I think I prefer it this way --
> > > it's simpler). Patch below for comment.
> > 
> > Umm...  I can live with that, assuming that we don't have callbacks
> > that take i_mutex themselves.  AFAICS, everything we call there is
> > either obviously not touching i_mutex or is already called while we
> > hold i_mutex elsewhere, but I'd appreciate if somebody actually
> > tested that sucker for different versions of protocol...
> 
> BTW, why mess with taking i_mutex inside the inner loop and not
> immediately around it?

Just to avoid making spaghetti of the bail-out cases, really. I did
consider it (it wouldn't be _that_ bad), but figured that it wasn't such
a bad thing if we don't hog the lock.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation


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