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[2003:d8:2f26:ba00:803:6ec5:9918:6fd]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-45b50e3a52bsm8600375e9.21.2025.08.21.13.07.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Aug 2025 13:07:39 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, "Liam R. Howlett" , Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Lorenzo Stoakes , Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, Zi Yan Subject: [PATCH RFC 12/35] mm: limit folio/compound page sizes in problematic kernel configs Date: Thu, 21 Aug 2025 22:06:38 +0200 Message-ID: <20250821200701.1329277-13-david@redhat.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250821200701.1329277-1-david@redhat.com> References: <20250821200701.1329277-1-david@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: JQ5WcKBAYlB_ob_qZFmZ-_LpicXsbAFEd3LxLXUqSrU_1755806861 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 1DE8340010 X-Stat-Signature: hqyh6qa9f5jiskayzi8nptp73uyid731 X-Rspam-User: X-HE-Tag: 1755806863-116047 X-HE-Meta: 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 KluEGDqU 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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: Let's limit the maximum folio size in problematic kernel config where the memmap is allocated per memory section (SPARSEMEM without SPARSEMEM_VMEMMAP) to a single memory section. Currently, only a single architectures supports ARCH_HAS_GIGANTIC_PAGE but not SPARSEMEM_VMEMMAP: sh. Fortunately, the biggest hugetlb size sh supports is 64 MiB (HUGETLB_PAGE_SIZE_64MB) and the section size is at least 64 MiB (SECTION_SIZE_BITS == 26), so their use case is not degraded. As folios and memory sections are naturally aligned to their order-2 size in memory, consequently a single folio can no longer span multiple memory sections on these problematic kernel configs. nth_page() is no longer required when operating within a single compound page / folio. Signed-off-by: David Hildenbrand --- include/linux/mm.h | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 77737cbf2216a..48a985e17ef4e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2053,11 +2053,25 @@ static inline long folio_nr_pages(const struct folio *folio) return folio_large_nr_pages(folio); } -/* Only hugetlbfs can allocate folios larger than MAX_ORDER */ -#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE -#define MAX_FOLIO_ORDER PUD_ORDER -#else +#if !defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) +/* + * We don't expect any folios that exceed buddy sizes (and consequently + * memory sections). + */ #define MAX_FOLIO_ORDER MAX_PAGE_ORDER +#elif defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) +/* + * Only pages within a single memory section are guaranteed to be + * contiguous. By limiting folios to a single memory section, all folio + * pages are guaranteed to be contiguous. + */ +#define MAX_FOLIO_ORDER PFN_SECTION_SHIFT +#else +/* + * There is no real limit on the folio size. We limit them to the maximum we + * currently expect. + */ +#define MAX_FOLIO_ORDER PUD_ORDER #endif #define MAX_FOLIO_NR_PAGES (1UL << MAX_FOLIO_ORDER) -- 2.50.1