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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tVZnh-00000002DWW-3y85; Wed, 08 Jan 2025 17:25:02 +0000 Date: Wed, 8 Jan 2025 17:25:01 +0000 From: Matthew Wilcox To: Lorenzo Stoakes Cc: Andrew Morton , Jaya Kumar , Simona Vetter , Helge Deller , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand Subject: Re: [RFC PATCH 2/3] mm: provide rmap_wrprotect_file_page() function Message-ID: References: <701a67692d5bf9c8424cdbda103c988bbb278e38.1736352361.git.lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <701a67692d5bf9c8424cdbda103c988bbb278e38.1736352361.git.lorenzo.stoakes@oracle.com> X-Rspamd-Queue-Id: 12173100023 X-Stat-Signature: 57ycoqbz37pgn5748pazr1ysphotkwr9 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1736357105-258769 X-HE-Meta: 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 Tk3LdvhT /VsxNbhzNpxxVV92aCzWAfAzz+jqPy01HhcmEleDsB22/upIyw5mqbtDIA/E2Fp5++v6MvE7oBhpFccMbDFRFucSIshOax0kfzUlNEM6FbAySlGtp/VdBHKFf2tJfJgcrzQQDOEE7TqaE9XON/fRtHlYHELcKjcsxKlYkLfDYNZVazbwYOkW6kmeEZEZMcoe31Io3J7FApbIr77v6Fu8O/lui8HUcqyCf7Qy1INoF9O3oAfi6ToV7uZSpEk+QRENPfuZliNq+RcUkMZiyV88hdlXRrQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000354, 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 Wed, Jan 08, 2025 at 04:18:41PM +0000, Lorenzo Stoakes wrote: > +++ b/include/linux/rmap.h > @@ -754,6 +754,26 @@ unsigned long page_address_in_vma(const struct folio *folio, > */ > int folio_mkclean(struct folio *); > > +/** The kerneldoc comment should be with the implementation, not the prototype. > + * rmap_wrprotect_file_page() - Traverses the reverse mapping, finding all VMAs > + * which contain a shared mapping of the single page at PFN @pfn in @mapping at > + * offset @pgoff and write-protecting the mappings. After the '-' should come a _short_ description ... maybe "Write protect all mappings of this page". > + * The PFN mapped does not have to be a folio, but rather can be a kernel > + * allocation that is mapped into userland. We therefore do not require that the > + * PFN maps to a folio with a valid mapping or index field, rather these are > + * specified in @mapping and @pgoff. > + * > + * @mapping: The mapping whose reverse mapping should be traversed. > + * @pgoff: The page offset at which @pfn is mapped within @mapping. > + * @nr_pages: The number of physically contiguous base pages spanned. > + * @pfn: The PFN of the memory mapped in @mapping at @pgoff. The description of the params comes between the short and full description of the function. > + * Return the number of write-protected PTEs, or an error. colon after Return: so it becomes a section. > +int rmap_wrprotect_file_page(struct address_space *mapping, pgoff_t pgoff, > + unsigned long nr_pages, unsigned long pfn) > +{ > + struct wrprotect_file_state state = { > + .cleaned = 0, > + .pgoff = pgoff, > + .pfn = pfn, > + .nr_pages = nr_pages, > + }; > + struct rmap_walk_control rwc = { > + .arg = (void *)&state, > + .rmap_one = rmap_wrprotect_file_one, > + .invalid_vma = invalid_mkclean_vma, > + }; > + > + if (!mapping) > + return 0; Should it be valid to pass in NULL?