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Date: Wed, 30 May 2018 11:11:19 +0200
From: Christoph Hellwig <hch@lst.de>
To: Huaisheng HS1 Ye <yehs1@lenovo.com>
Cc: Michal Hocko <mhocko@kernel.org>,
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        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>
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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.