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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 , 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 v1 11/36] mm: limit folio/compound page sizes in problematic kernel configs Date: Thu, 28 Aug 2025 00:01:15 +0200 Message-ID: <20250827220141.262669-12-david@redhat.com> In-Reply-To: <20250827220141.262669-1-david@redhat.com> References: <20250827220141.262669-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 1A3A21C0006 X-Stat-Signature: 36x58tu487dcxb8smj49agngyx88oapz X-Rspam-User: X-HE-Tag: 1756332336-112715 X-HE-Meta: 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 dX9rNLrF 9rDoE/GErs+PY4wfaT8DD5K701Tl3wJDf9shwCmAtisjn5xV46zzSjEHcOw== 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) 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