From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752093AbbCYXJt (ORCPT <rfc822;w@1wt.eu>);
	Wed, 25 Mar 2015 19:09:49 -0400
Received: from mail-pa0-f46.google.com ([209.85.220.46]:36471 "EHLO
	mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1750807AbbCYXJs (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 25 Mar 2015 19:09:48 -0400
Date: Wed, 25 Mar 2015 16:09:38 -0700 (PDT)
From: Hugh Dickins <hughd@google.com>
X-X-Sender: hugh@eggly.anvils
To: "Kirill A. Shutemov" <kirill@shutemov.name>
cc: Hugh Dickins <hughd@google.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm: avoid tail page refcounting on non-THP compound
 pages
In-Reply-To: <20150325225633.GA14549@node.dhcp.inet.fi>
Message-ID: <alpine.LSU.2.11.1503251602570.4703@eggly.anvils>
References: <1427323275-114866-1-git-send-email-kirill.shutemov@linux.intel.com> <alpine.LSU.2.11.1503251544120.4490@eggly.anvils> <alpine.LSU.2.11.1503251545510.4490@eggly.anvils> <20150325225633.GA14549@node.dhcp.inet.fi>
User-Agent: Alpine 2.11 (LSU 23 2013-08-11)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 26 Mar 2015, Kirill A. Shutemov wrote:
> On Wed, Mar 25, 2015 at 03:48:48PM -0700, Hugh Dickins wrote:
> > On Wed, 25 Mar 2015, Hugh Dickins wrote:
> > > On Thu, 26 Mar 2015, Kirill A. Shutemov wrote:
> > > > 
> > > > Since currently all THP pages are anonymous and all drivers pages are
> > > > not, we can fix the __compound_tail_refcounted() check by requiring
> > > > PageAnon() to enable tail page refcounting.
> > > > 
> > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > > 
> > > Acked-by: Hugh Dickins <hughd@google.com>
> > 
> > Oh, hold on a moment: does this actually build in a tree without your
> > page-flags.h consolidation?  It didn't when I tried to add a PageAnon
> > test there for my series against v3.19, has something changed in v4.0?
> 
> No. I haven't tried to build it without my patchset, but it seems it
> wouldn't.
> 
> Just check: it would build for me on top of [PATCH 01/16], you've acked.

Yes, I'm happy with your 1/16 (which is already there in mmotm),
it's just that I'd imagined this __compound_tail_refcounted() fix
should go to v4.0 (if not stable too: you've decided against, okay).

What do you think, should Andrew hold it back for v4.1, or should
your page-flags.h accelerate into v4.0 as precondition for this fix?

Either is fine with me; but if the latter, then a week's exposure
in linux-next first would probably be best.

Hugh