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[213.95.11.211]) by mx.google.com with ESMTPS id g133si29883049wmf.83.2019.07.22.02.36.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jul 2019 02:36:59 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by verein.lst.de (Postfix, from userid 2407) id F1AF268B20; Mon, 22 Jul 2019 11:36:56 +0200 (CEST) Date: Mon, 22 Jul 2019 11:36:56 +0200 From: Christoph Hellwig To: Matthew Wilcox Cc: Ralph Campbell , linux-mm@kvack.org, linux-kernel@vger.kernel.org, John Hubbard , Vlastimil Babka , Christoph Lameter , Dave Hansen , =?iso-8859-1?B?Suly9G1l?= Glisse , "Kirill A . Shutemov" , Lai Jiangshan , Martin Schwidefsky , Pekka Enberg , Randy Dunlap , Andrey Ryabinin , Christoph Hellwig , Jason Gunthorpe , Andrew Morton , Linus Torvalds Subject: Re: [PATCH v2 1/3] mm: document zone device struct page field usage Message-ID: <20190722093656.GD29538@lst.de> References: <20190719192955.30462-1-rcampbell@nvidia.com> <20190719192955.30462-2-rcampbell@nvidia.com> <20190721160204.GB363@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190721160204.GB363@bombadil.infradead.org> User-Agent: Mutt/1.5.17 (2007-11-01) 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 Sun, Jul 21, 2019 at 09:02:04AM -0700, Matthew Wilcox wrote: > On Fri, Jul 19, 2019 at 12:29:53PM -0700, Ralph Campbell wrote: > > Struct page for ZONE_DEVICE private pages uses the page->mapping and > > and page->index fields while the source anonymous pages are migrated to > > device private memory. This is so rmap_walk() can find the page when > > migrating the ZONE_DEVICE private page back to system memory. > > ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and > > page->index fields when files are mapped into a process address space. > > > > Restructure struct page and add comments to make this more clear. > > NAK. I just got rid of this kind of foolishness from struct page, > and you're making it harder to understand, not easier. The comments > could be improved, but don't lay it out like this again. This comes over pretty agressive. Please explain how making the layout match how the code actually is used vs the previous separation that is actively misleading and confused multiple people is "foolishness".