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Howlett" , 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, 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, Marco Elver , Marek Szyprowski , Michal Hocko , 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 Subject: [PATCH v2 11/37] mm: limit folio/compound page sizes in problematic kernel configs Date: Mon, 1 Sep 2025 17:03:32 +0200 Message-ID: <20250901150359.867252-12-david@redhat.com> In-Reply-To: <20250901150359.867252-1-david@redhat.com> References: <20250901150359.867252-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Stat-Signature: hoex3f1dowr5ug56wpc4qn8bsbym8coj X-Rspam-User: X-Rspamd-Queue-Id: 172C9A0011 X-Rspamd-Server: rspam05 X-HE-Tag: 1756739257-172141 X-HE-Meta: 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 YRqsOiPT y1JsD0OsfPEV3DvoD5yqrK1h+g5FgUi4Wb3IAk1lufWFxwaecwkP6w45fSLyYdecLysQGI3g9J368c4RPFGnSie/OZ0h6kvLs9QHk9AuzNhyeKCgsemE1ffXdx7EIlTKKEwQdbVMcI/Vx9w4ov7g2O3Qf28OGhQB7+dfXLlJIKyDV+YRoAC+RzUh886mI7CQcE2ZDsaXMcsdSTzOB8dI60l1kBnmYqRYq9K14CaggYkUuyK9ZdqwPRO8oOnknkfR330AFQ8Gv1qmJUw1HYO1zWzyrHnDmPMhyAo10zvsjcPrwF8mDNRIkTvggPrgTg7HTv0AVgZrVjSF/Y4hobidOggFIp3gj+L0B2CVc8vQdpMHti88bNOWWLQBeyHya8/fF8Hf7Q8mMVMvBtpAwvNBPu/8cY38odRiwSkjeVywouN3kZtWA2dimWFRe/6lImi4D2fkBdHbUZGOXI0gVX+gKAQURiYIcZAUqPiYqEDr5b6mI1slpvz96R8AESw== 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. Reviewed-by: Zi Yan Acked-by: Mike Rapoport (Microsoft) Reviewed-by: Wei Yang Reviewed-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett 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..2dee79fa2efcf 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 (e.g., hugetlb, dax). + */ +#define MAX_FOLIO_ORDER PUD_ORDER #endif #define MAX_FOLIO_NR_PAGES (1UL << MAX_FOLIO_ORDER) -- 2.50.1