From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mail-ed1-f66.google.com ([209.85.208.66]:42795 "EHLO
        mail-ed1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1727037AbeJRAp3 (ORCPT
        <rfc822;linux-fsdevel@vger.kernel.org>);
        Wed, 17 Oct 2018 20:45:29 -0400
Received: by mail-ed1-f66.google.com with SMTP id b7-v6so25507645edd.9
        for <linux-fsdevel@vger.kernel.org>; Wed, 17 Oct 2018 09:48:56 -0700 (PDT)
Date: Wed, 17 Oct 2018 18:48:48 +0200
From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: David Howells <dhowells@redhat.com>
Cc: gregkh@linux-foundation.org,
        Kiran Kumar Modukuri <kiran.modukuri@gmail.com>,
        viro@zeniv.linux.org.uk, sandeen@redhat.com,
        linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] fscache: Fix race in fscache_op_complete() due to
 split atomic_sub & read
Message-ID: <20181017164848.GA9795@andrea>
References: <20181017151134.GA8966@andrea>
 <153978619457.8478.3813964117489247515.stgit@warthog.procyon.org.uk>
 <153978621809.8478.2198040871218302573.stgit@warthog.procyon.org.uk>
 <14408.1539790333@warthog.procyon.org.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <14408.1539790333@warthog.procyon.org.uk>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Wed, Oct 17, 2018 at 04:32:13PM +0100, David Howells wrote:
> Andrea Parri <andrea.parri@amarulasolutions.com> wrote:
> 
> > > Fix this by using atomic_sub_return() instead of two calls.
> > 
> > Seems a case for atomic_sub_return_relaxed()... why not?
> 
> Ummm...  In that case, should it be atomic_sub_return_release()?

Hard to tell for me: your diff./changelog is all I know about fs-cache
... (and this suggests -no-, given that atomic_sub() and atomic_read()
provide no ordering...); good question though. ;-)

  Andrea


> 
> David