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Fri, 04 Jul 2025 01:21:47 -0700 (PDT) From: lizhe.67@bytedance.com To: david@redhat.com Cc: akpm@linux-foundation.org, alex.williamson@redhat.com, jgg@ziepe.ca, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lizhe.67@bytedance.com, peterx@redhat.com Subject: Re: [PATCH v2 1/5] mm: introduce num_pages_contiguous() Date: Fri, 4 Jul 2025 16:21:30 +0800 Message-ID: <20250704082130.11804-1-lizhe.67@bytedance.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <97d3993c-12aa-4917-9bbd-d9c94fbda788@redhat.com> References: <97d3993c-12aa-4917-9bbd-d9c94fbda788@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: fe1y49tbwwjpb56wfdxm5zn8swhs6mfd X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 576371C0003 X-HE-Tag: 1751617309-201254 X-HE-Meta: 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 tHuL08hd ptjTOjrpzFp8721N4M2ztlfF1+k4cZ5lT7Kgfdkuz/c8x4nAgA8+C4PX0RdOufS976pIpX2GlK90GJUpGbaw1Af3q+zt6dwTC8E6iW4xJZw3aiA/fkL4vgbRtL0eaBlbvFyfr6wgHfbxewIHupxzCFIYOgSmI1lAdEqxfWfvqqmGh/KQJZE9NLCJ3AK4LUzBW3xUiDadkQUpKLIwvrePiD1p/qOWsPGxYQqPdAXr3dRYkwnXu4Jc1sREt1c8ID3S7yzMd+1SuGpRUODx68XWejXgt8trLKY8prRR51N5NGxnr7aaMJqdL/B0pw3IU6DU8jQGkxWkTpLZn3LGjhhbl2dqSsS3bmSwfOMxAMFGl7Kk+Njt1Gcgjsrj5gXBjidnjWTiA2sLyyM7x7S9bGPKIZ613ig1jvgPeTmifQkVK1jbO9jktc3tInyF/tXoeMlrN1R8bEwwmdRWSY66oK02qz2PGvQ== 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 Fri, 4 Jul 2025 09:56:23 +0200, david@redhat.com wrote: > On 04.07.25 08:25, lizhe.67@bytedance.com wrote: > > From: Li Zhe > > > > Function num_pages_contiguous() determine the number of contiguous > > pages starting from the first page in the given array of page pointers. > > VFIO will utilize this interface to accelerate the VFIO DMA map process. > > > > Suggested-by: David Hildenbrand > > I think Jason suggested having this as a helper as well. Yes, thank you for the reminder. Jason needs to be added here. Suggested-by: Jason Gunthorpe > > Signed-off-by: Li Zhe > > --- > > include/linux/mm.h | 20 ++++++++++++++++++++ > > 1 file changed, 20 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 0ef2ba0c667a..1d26203d1ced 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -205,6 +205,26 @@ extern unsigned long sysctl_admin_reserve_kbytes; > > #define folio_page_idx(folio, p) ((p) - &(folio)->page) > > #endif > > > > +/* > > + * num_pages_contiguous() - determine the number of contiguous pages > > + * starting from the first page. > > Maybe clarify here here: > > "Pages are contiguous if they represent contiguous PFNs. Depending on > the memory model, this can mean that the addresses of the "struct page"s > are not contiguous." Thank you. I will include this clarification in the comment. > > + * > > + * @pages: an array of page pointers > > + * @nr_pages: length of the array > > + */ > > +static inline unsigned long num_pages_contiguous(struct page **pages, > > + unsigned long nr_pages) > > +{ > > + struct page *first_page = pages[0]; > > + unsigned long i; > > + > > + for (i = 1; i < nr_pages; i++) > > + if (pages[i] != nth_page(first_page, i)) > > if (pages[i] != nth_page(pages[0], i)) > > Should be clear as well, so no need for the temporary "first_page" variable. Thank you. Doing so makes the function appear much clearer. > Apart from that LGTM. Thank you for your review! Thanks, Zhe