Subject: Re: Q: NFSD readdir in linux-2.6.28
From: David Woodhouse <dwmw2@infradead.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: hooanon05@yahoo.co.jp, hch@infradead.org,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
In-Reply-To: <20090417225306.GO26366@ZenIV.linux.org.uk>
References: <8036.1237474444@jrobl>
	 <1237475837.16359.106.camel@macbook.infradead.org> <8913.1237476890@jrobl>
	 <1239960739.3428.33.camel@macbook.infradead.org>
	 <20090417193233.GM26366@ZenIV.linux.org.uk>
	 <1240006620.19059.41.camel@macbook.infradead.org>
	 <20090417224350.GN26366@ZenIV.linux.org.uk>
	 <20090417225306.GO26366@ZenIV.linux.org.uk>
Content-Type: text/plain
Date: Fri, 17 Apr 2009 23:55:46 +0100
Message-Id: <1240008946.21423.18.camel@macbook.infradead.org>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1544
Lines: 32

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@intel.com                              Intel Corporation


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/