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 S1031319AbdD0MSH (ORCPT <rfc822;w@1wt.eu>);
        Thu, 27 Apr 2017 08:18:07 -0400
Received: from lhrrgout.huawei.com ([194.213.3.17]:25368 "EHLO
        lhrrgout.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S933442AbdD0MRz (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 27 Apr 2017 08:17:55 -0400
Subject: Question on ___GFP_NOLOCKDEP - Was: Re: [PATCH 1/1] Remove hardcoding
 of ___GFP_xxx bitmasks
To: Michal Hocko <mhocko@kernel.org>
References: <20170426133549.22603-1-igor.stoppa@huawei.com>
 <20170426133549.22603-2-igor.stoppa@huawei.com>
 <20170426144750.GH12504@dhcp22.suse.cz>
 <e3fe4d80-10a8-2008-1798-af3893fe418a@huawei.com>
CC: <namhyung@kernel.org>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>
From: Igor Stoppa <igor.stoppa@huawei.com>
Message-ID: <9929419e-c22e-2a9f-a8a6-ad98d5a9da06@huawei.com>
Date: Thu, 27 Apr 2017 15:16:47 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.8.0
MIME-Version: 1.0
In-Reply-To: <e3fe4d80-10a8-2008-1798-af3893fe418a@huawei.com>
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.122.225.51]
X-CFilter-Loop: Reflected
X-Mirapoint-Virus-RAPID-Raw: score=unknown(0),
        refid=str=0001.0A0B0201.5901E167.018E,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0,
        ip=0.0.0.0,
        so=2013-06-18 04:22:30,
        dmn=2013-03-21 17:37:32
X-Mirapoint-Loop-Id: d43508e060c121f874b6fa55c650f03d
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 26/04/17 18:29, Igor Stoppa wrote:

> On 26/04/17 17:47, Michal Hocko wrote:

[...]

>> Also the current mm tree has ___GFP_NOLOCKDEP which is not addressed
>> here so I suspect you have based your change on the Linus tree.

> I used your tree from kernel.org

I found it, I was using master, instead of auto-latest (is it correct?)
But now I see something that I do not understand (apologies if I'm
asking something obvious).

First there is:

[...]
#define ___GFP_WRITE		0x800000u
#define ___GFP_KSWAPD_RECLAIM	0x1000000u
#ifdef CONFIG_LOCKDEP
#define ___GFP_NOLOCKDEP	0x4000000u
#else
#define ___GFP_NOLOCKDEP	0
#endif

Then:

/* Room for N __GFP_FOO bits */
#define __GFP_BITS_SHIFT (25 + IS_ENABLED(CONFIG_LOCKDEP))



Shouldn't it be either:
___GFP_NOLOCKDEP	0x2000000u

or:

#define __GFP_BITS_SHIFT (25 + 2 * IS_ENABLED(CONFIG_LOCKDEP))


thanks, igor