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Wed, 25 Jun 2025 08:32:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id QkyABSm0W2jmHwAAD6G6ig (envelope-from ); Wed, 25 Jun 2025 08:32:41 +0000 Date: Wed, 25 Jun 2025 10:32:31 +0200 From: Oscar Salvador To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato Subject: Re: [PATCH RFC 08/14] mm/huge_memory: mark PMD mappings of the huge zero folio special Message-ID: References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-9-david@redhat.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250617154345.2494405-9-david@redhat.com> X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Queue-Id: 8E4F51F441 X-Rspamd-Action: no action X-Spam-Flag: NO X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[29]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received,2a07:de40:b281:104:10:150:64:97:from]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; TO_DN_SOME(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_RATELIMIT(0.00)[to_ip_from(RL88oxspsx4bg3gu1yybyqiqt4)]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -4.51 X-Spam-Level: On Tue, Jun 17, 2025 at 05:43:39PM +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. > > Signed-off-by: David Hildenbrand Reviewed-by: Oscar Salvador While doing this, would it make sense to update vm_normal_page_pmd() comments to refelect that pmd_special will also catch huge_zero_folio()? It only mentions huge pfnmaps. It might not be worth doing since you remove that code later on, but maybe if someone stares at this commit alone.. -- Oscar Salvador SUSE Labs