From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [GIT PULL] overlay filesystem v25
Date: Tue, 28 Oct 2014 22:55:13 +0000
Message-ID: <20141028225512.GD7996@ZenIV.linux.org.uk>
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Cc: Miklos Szeredi <miklos@szeredi.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
	Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-unionfs@vger.kernel.org
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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On Mon, Oct 27, 2014 at 09:11:27PM -0700, Paul E. McKenney wrote:
> On Tue, Oct 28, 2014 at 01:12:14AM +0000, Al Viro wrote:
> > On Mon, Oct 27, 2014 at 10:36:21AM -0700, Paul E. McKenney wrote:
> > > Code making direct use of smp_read_barrier_depends() is harder to read,
> > > in my experience, but good point on the sparse noise.  Maybe a new
> > > lockless_dereference() primitive?  Maybe something like the following?
> > > (Untested, probably does not even build.)
> > > 
> > > #define lockless_dereference(p) \
> > > ({ \
> > > 	typeof(*p) *_________p1 = ACCESS_ONCE(p); \
> > > 	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
> > > 	_________p1; \
> > > })
> > 
> > Hmm...  Where would you prefer to put it?  rcupdate.h?
> 
> Good a place as any, I guess.  Please see patch below.  Left to myself,
> I would send this along for the next merge window, but please let me
> know if you would like it sooner.

It's needed sooner, unfortunately.  Guys, could you take a look at
vfs.git#for-linus and comment?