From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 3CABA6B000C for ; Sun, 6 May 2018 09:48:21 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id e3so3723843pfe.15 for ; Sun, 06 May 2018 06:48:21 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id j10-v6si19744369plg.396.2018.05.06.06.48.19 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 06 May 2018 06:48:19 -0700 (PDT) Date: Sun, 6 May 2018 06:48:14 -0700 From: Matthew Wilcox Subject: Re: [External] Re: [PATCH 2/3] include/linux/gfp.h: use unsigned int in gfp_zone Message-ID: <20180506134814.GB7362@bombadil.infradead.org> References: <1525416729-108201-1-git-send-email-yehs1@lenovo.com> <1525416729-108201-3-git-send-email-yehs1@lenovo.com> <20180504133533.GR4535@dhcp22.suse.cz> <20180504154004.GB29829@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Huaisheng HS1 Ye Cc: Michal Hocko , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "vbabka@suse.cz" , "mgorman@techsingularity.net" , "pasha.tatashin@oracle.com" , "alexander.levin@verizon.com" , "hannes@cmpxchg.org" , "penguin-kernel@I-love.SAKURA.ne.jp" , "colyli@suse.de" , NingTing Cheng , "linux-kernel@vger.kernel.org" On Sun, May 06, 2018 at 09:32:15AM +0000, Huaisheng HS1 Ye wrote: > This idea is great, we can replace GFP_ZONE_TABLE and GFP_ZONE_BAD with it. > I have realized it preliminarily based on your code and tested it on a 2 sockets platform. Fortunately, we got a positive test result. Great! > I made some adjustments for __GFP_HIGHMEM, this flag is special than others, because the return result of gfp_zone has two possibilities, which depend on ___GFP_MOVABLE has been enabled or disabled. > When ___GFP_MOVABLE has been enabled, ZONE_MOVABLE shall be returned. When disabled, OPT_ZONE_HIGHMEM shall be used. > > #define __GFP_DMA ((__force gfp_t)OPT_ZONE_DMA ^ ZONE_NORMAL) > #define __GFP_HIGHMEM ((__force gfp_t)ZONE_MOVABLE ^ ZONE_NORMAL) I'm not sure this is right ... Let me think about this a little. > #define __GFP_DMA32 ((__force gfp_t)OPT_ZONE_DMA32 ^ ZONE_NORMAL) > #define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ > #define GFP_ZONEMASK ((__force gfp_t)___GFP_ZONE_MASK | ___GFP_MOVABLE) > > The present situation is that, based on this change, the bits of flags, __GFP_DMA and __GFP_HIGHMEM and __GFP_DMA32, have been encoded. > That is totally different from existing code, you know in kernel scope, there are many drivers or subsystems use these flags directly to realize bit manipulations like this below, > swiotlb-xen.c (drivers\xen): flags &= ~(__GFP_DMA | __GFP_HIGHMEM); > extent_io.c (fs\btrfs): mask &= ~(__GFP_DMA32|__GFP_HIGHMEM); > > Because of these flags have been encoded, the above operations can cause problem. > I am trying to get a solution to resolve it. Any progress will be reported. These users probably want: flags &= GFP_RECLAIM_MASK;