From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200])
	by kanga.kvack.org (Postfix) with ESMTP id 0A3A36B0008
	for <linux-mm@kvack.org>; Wed, 30 May 2018 05:05:01 -0400 (EDT)
Received: by mail-wr0-f200.google.com with SMTP id a7-v6so14667518wrq.13
        for <linux-mm@kvack.org>; Wed, 30 May 2018 02:05:00 -0700 (PDT)
Received: from newverein.lst.de (verein.lst.de. [213.95.11.211])
        by mx.google.com with ESMTPS id v8-v6si7137658wmg.221.2018.05.30.02.04.59
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Wed, 30 May 2018 02:04:59 -0700 (PDT)
Date: Wed, 30 May 2018 11:11:19 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [External]  Re: [RFC PATCH v2 00/12] get rid of
	GFP_ZONE_TABLE/BAD
Message-ID: <20180530091119.GA30154@lst.de>
References: <1526916033-4877-1-git-send-email-yehs2007@gmail.com> <20180522183728.GB20441@dhcp22.suse.cz> <HK2PR03MB16847646E90A10E2D48CEA8E926B0@HK2PR03MB1684.apcprd03.prod.outlook.com> <20180524121853.GG20441@dhcp22.suse.cz> <HK2PR03MB1684ED6EC6859A88A196DC0C92690@HK2PR03MB1684.apcprd03.prod.outlook.com> <20180528133733.GF27180@dhcp22.suse.cz> <HK2PR03MB1684C44F2408F3927B1A21BC926C0@HK2PR03MB1684.apcprd03.prod.outlook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <HK2PR03MB1684C44F2408F3927B1A21BC926C0@HK2PR03MB1684.apcprd03.prod.outlook.com>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Huaisheng HS1 Ye <yehs1@lenovo.com>
Cc: Michal Hocko <mhocko@kernel.org>, "akpm@linux-foundation.org" <akpm@linux-foundation.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "willy@infradead.org" <willy@infradead.org>, "vbabka@suse.cz" <vbabka@suse.cz>, "mgorman@techsingularity.net" <mgorman@techsingularity.net>, "kstewart@linuxfoundation.org" <kstewart@linuxfoundation.org>, "alexander.levin@verizon.com" <alexander.levin@verizon.com>, "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>, "colyli@suse.de" <colyli@suse.de>, NingTing Cheng <chengnt@lenovo.com>, Ocean HY1 He <hehy1@lenovo.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>, "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>, "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>, Christoph Hellwig <hch@lst.de>

On Wed, May 30, 2018 at 09:02:13AM +0000, Huaisheng HS1 Ye wrote:
> 
> I don't quite understand that. I think those, mostly drivers, need to
> get the correct zone they want. ZONE_DMA32 is an example, if drivers can be
> satisfied with a low mem zone, why they mark the gfp flags as
> 'GFP_KERNEL|__GFP_DMA32'?

Drivers should never use GFP_DMA32 directly.  The right abstraction is
the DMA API, ZONE_DMA32 is just a helper.