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Howlett" To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Zi Yan , "Mike Rapoport (Microsoft)" , 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, 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: Re: [PATCH v1 11/36] mm: limit folio/compound page sizes in problematic kernel configs Message-ID: Mail-Followup-To: "Liam R. 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tKpw3NFGxJgpwvqCU35UWH1S0dRSbgFAy/W9WpLZwh0jK4DlNqosQy+73xK7uC3517aTYbsV/44 doIy1h6Jo1YWgLfIeUY8JtRLyjWskB8Gi39I/0W3r/yQsTP3pxzNKrQln9ChEfzKThRvu606NLR vngWVG59+tJ1hhSJOEmb0h0PARA63+d6L7oPvm+Cq8tNWuqGtUn4+rY3gTbtPxwPoC93UTMvBQN yV2d3l0O X-Proofpoint-GUID: 1t32yqI8iiw3TUyJC_y4AtEWXZiUd87R X-Authority-Analysis: v=2.4 cv=IZWHWXqa c=1 sm=1 tr=0 ts=68b1b90d b=1 cx=c_pps a=WeWmnZmh0fydH62SvGsd2A==:117 a=WeWmnZmh0fydH62SvGsd2A==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=2OwXVqhp2XgA:10 a=GoEa3M9JfhUA:10 a=20KFwNOVAAAA:8 a=Ikd4Dj_1AAAA:8 a=VwQbUJbxAAAA:8 a=yPCof4ZbAAAA:8 a=r2OVo3NODdYC9qRF9NoA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: 1t32yqI8iiw3TUyJC_y4AtEWXZiUd87R * David Hildenbrand [250827 18:05]: > 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 Reviewed-by: Liam R. Howlett > --- > 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 >