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Tue, 8 Feb 2022 02:25:20 +0000 Received: from MN2PR12MB4344.namprd12.prod.outlook.com ([fe80::6872:c444:d3b5:7b2e]) by MN2PR12MB4344.namprd12.prod.outlook.com ([fe80::6872:c444:d3b5:7b2e%8]) with mapi id 15.20.4951.019; Tue, 8 Feb 2022 02:25:20 +0000 Message-ID: <8478b7c5-5079-5c5c-04cd-54a313e3f7c4@nvidia.com> Date: Mon, 7 Feb 2022 18:25:15 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH 7/8] mm: remove the extra ZONE_DEVICE struct page refcount Content-Language: en-US To: Christoph Hellwig , Andrew Morton , Dan Williams Cc: Felix Kuehling , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= , "Pan, Xinhui" , Ben Skeggs , Karol Herbst , Lyude Paul , Jason Gunthorpe , Alistair Popple , Logan Gunthorpe , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, nvdimm@lists.linux.dev, linux-mm@kvack.org References: <20220207063249.1833066-1-hch@lst.de> <20220207063249.1833066-8-hch@lst.de> From: Ralph Campbell In-Reply-To: <20220207063249.1833066-8-hch@lst.de> Content-Type: text/plain; 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=F2LlJsFc; spf=none (imf16.hostedemail.com: domain of rcampbell@nvidia.com has no SPF policy when checking 40.107.93.61) smtp.mailfrom=rcampbell@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E4B94180004 X-HE-Tag: 1644287123-297823 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/6/22 22:32, Christoph Hellwig wrote: > ZONE_DEVICE struct pages have an extra reference count that complicates > the code for put_page() and several places in the kernel that need to > check the reference count to see that a page is not being used (gup, > compaction, migration, etc.). Clean up the code so the reference count > doesn't need to be treated specially for ZONE_DEVICE pages. > > Note that this excludes the special idle page wakeup for fsdax pages, > which still happens at refcount 1. This is a separate issue and will > be sorted out later. Given that only fsdax pages require the > notifiacation when the refcount hits 1 now, the PAGEMAP_OPS Kconfig > symbol can go away and be replaced with a FS_DAX check for this hook > in the put_page fastpath. > > Based on an earlier patch from Ralph Campbell . > > Signed-off-by: Christoph Hellwig Thanks for working on this, definite step forward. Reviewed-by: Ralph Campbell