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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q9tNO-0082yB-UE; Thu, 15 Jun 2023 20:15:26 +0000 Date: Thu, 15 Jun 2023 21:15:26 +0100 From: Matthew Wilcox To: Peter Xu Cc: Alex Sierra , jgg@nvidia.com, david@redhat.com, Felix.Kuehling@amd.com, linux-mm@kvack.org, rcampbell@nvidia.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jglisse@redhat.com, apopple@nvidia.com, akpm@linux-foundation.org Subject: Re: [PATCH v9 02/14] mm: move page zone helpers from mm.h to mmzone.h Message-ID: References: <20220715150521.18165-1-alex.sierra@amd.com> <20220715150521.18165-3-alex.sierra@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 68F9814001A X-Stat-Signature: 6da6rqm8ueq1ju4upbiw95z5j1md3nhw X-Rspam-User: X-HE-Tag: 1686860139-667684 X-HE-Meta: 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 t5Ul6khh XM8hDSSSwX3AbuGfBVSTBLJGDIiCZiXqvfjLr70tQj8bqJo7CB8ahd4BZE+CW6JBnI2iuOEZ7TcBjdilgMuNQj+oGf2J3cRFJDerV9NCReD3RY1oy3R9WwVK4lVN8M91ROXODef0DWJUDS5k= 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 Thu, Jun 15, 2023 at 03:33:12PM -0400, Peter Xu wrote: > My question is whether page_zonenum() is ready for taking all kinds of tail > pages? > > Zone device tail pages all look fine, per memmap_init_zone_device(). The > question was other kinds of usual compound pages, like either thp or > hugetlb. IIUC page->flags can be uninitialized for those tail pages. I don't think that's true. It's my understanding that page->flags is initialised for all pages in memmap at boot / hotplug / delayed-init time. So you can check things like zone, node, etc on literally any page. Contrariwise, those flags are not available in tail pages for use by the entity that has allocated a compound page / large folio. Also, I don't believe zone device pages support compound allocation. I think they're always allocated as order-0.