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Mon, 28 Jul 2025 01:49:55 -0700 (PDT) Date: Mon, 28 Jul 2025 08:49:55 +0000 From: Wei Yang To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, xen-devel@lists.xenproject.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Jann Horn , Pedro Falcato , Hugh Dickins , Oscar Salvador , Lance Yang Subject: Re: [PATCH v2 5/9] mm/huge_memory: mark PMD mappings of the huge zero folio special Message-ID: <20250728084955.uzobxwoqalcuhk72@master> Reply-To: Wei Yang References: <20250717115212.1825089-1-david@redhat.com> <20250717115212.1825089-6-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250717115212.1825089-6-david@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Stat-Signature: n1mtrsuz5c9fm4tudtr813an6b7de7u9 X-Rspam-User: X-Rspamd-Queue-Id: 2AD8D140006 X-Rspamd-Server: rspam02 X-HE-Tag: 1753692597-678973 X-HE-Meta: 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 lTcqG38P 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 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: List-Subscribe: List-Unsubscribe: On Thu, Jul 17, 2025 at 01:52:08PM +0200, David Hildenbrand wrote: >The huge zero folio is refcounted (+mapcounted -- is that a word?) >differently than "normal" folios, similarly (but different) to the ordinary >shared zeropage. > >For this reason, we special-case these pages in >vm_normal_page*/vm_normal_folio*, and only allow selected callers to >still use them (e.g., GUP can still take a reference on them). > >vm_normal_page_pmd() already filters out the huge zero folio. However, >so far we are not marking it as special like we do with the ordinary >shared zeropage. Let's mark it as special, so we can further refactor >vm_normal_page_pmd() and vm_normal_page(). > >While at it, update the doc regarding the shared zero folios. > >Reviewed-by: Oscar Salvador >Signed-off-by: David Hildenbrand Reviewed-by: Wei Yang -- Wei Yang Help you, Help me