mirror of
https://github.com/torvalds/linux.git
synced 2026-07-31 03:27:03 +02:00
Linux kernel source tree
f8f03eb5f0
Patch series "mm: remove nth_page()", v2. As discussed recently with Linus, nth_page() is just nasty and we would like to remove it. To recap, the reason we currently need nth_page() within a folio is because on some kernel configs (SPARSEMEM without SPARSEMEM_VMEMMAP), the memmap is allocated per memory section. While buddy allocations cannot cross memory section boundaries, hugetlb and dax folios can. So crossing a memory section means that "page++" could do the wrong thing. Instead, nth_page() on these problematic configs always goes from page->pfn, to the go from (++pfn)->page, which is rather nasty. Likely, many people have no idea when nth_page() is required and when it might be dropped. We refer to such problematic PFN ranges and "non-contiguous pages". If we only deal with "contiguous pages", there is not need for nth_page(). Besides that "obvious" folio case, we might end up using nth_page() within CMA allocations (again, could span memory sections), and in one corner case (kfence) when processing memblock allocations (again, could span memory sections). So let's handle all that, add sanity checks, and remove nth_page(). Patch #1 -> #5 : stop making SPARSEMEM_VMEMMAP user-selectable + cleanups Patch #6 -> #13 : disallow folios to have non-contiguous pages Patch #14 -> #20 : remove nth_page() usage within folios Patch #22 : disallow CMA allocations of non-contiguous pages Patch #23 -> #33 : sanity+check + remove nth_page() usage within SG entry Patch #34 : sanity-check + remove nth_page() usage in unpin_user_page_range_dirty_lock() Patch #35 : remove nth_page() in kfence Patch #36 : adjust stale comment regarding nth_page Patch #37 : mm: remove nth_page() A lot of this is inspired from the discussion at [1] between Linus, Jason and me, so cudos to them. This patch (of 37): In an ideal world, we wouldn't have to deal with SPARSEMEM without SPARSEMEM_VMEMMAP, but in particular for 32bit SPARSEMEM_VMEMMAP is considered too costly and consequently not supported. However, if an architecture does support SPARSEMEM with SPARSEMEM_VMEMMAP, let's forbid the user to disable VMEMMAP: just like we already do for arm64, s390 and x86. So if SPARSEMEM_VMEMMAP is supported, don't allow to use SPARSEMEM without SPARSEMEM_VMEMMAP. This implies that the option to not use SPARSEMEM_VMEMMAP will now be gone for loongarch, powerpc, riscv and sparc. All architectures only enable SPARSEMEM_VMEMMAP with 64bit support, so there should not really be a big downside to using the VMEMMAP (quite the contrary). This is a preparation for not supporting (1) folio sizes that exceed a single memory section (2) CMA allocations of non-contiguous page ranges in SPARSEMEM without SPARSEMEM_VMEMMAP configs, whereby we want to limit possible impact as much as possible (e.g., gigantic hugetlb page allocations suddenly fails). Link: https://lkml.kernel.org/r/20250901150359.867252-1-david@redhat.com Link: https://lkml.kernel.org/r/20250901150359.867252-2-david@redhat.com Link: https://lore.kernel.org/all/CAHk-=wiCYfNp4AJLBORU-c7ZyRBUp66W2-Et6cdQ4REx-GyQ_A@mail.gmail.com/T/#u [1] Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Zi Yan <ziy@nvidia.com> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Acked-by: SeongJae Park <sj@kernel.org> Reviewed-by: Wei Yang <richard.weiyang@gmail.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: "David S. Miller" <davem@davemloft.net> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Alexander Potapenko <glider@google.com> Cc: Alexandru Elisei <alexandru.elisei@arm.com> Cc: Alex Dubov <oakad@yahoo.com> Cc: Alex Willamson <alex.williamson@redhat.com> Cc: Bart van Assche <bvanassche@acm.org> Cc: Borislav Betkov <bp@alien8.de> Cc: Brendan Jackman <jackmanb@google.com> Cc: Brett Creeley <brett.creeley@amd.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christoph Lameter (Ampere) <cl@gentwo.org> Cc: Damien Le Maol <dlemoal@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Dmitriy Vyukov <dvyukov@google.com> Cc: Doug Gilbert <dgilbert@interlog.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Ingo Molnar <mingo@redhat.com> Cc: Inki Dae <m.szyprowski@samsung.com> Cc: James Bottomley <james.bottomley@HansenPartnership.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Jason A. Donenfeld <jason@zx2c4.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Kevin Tian <kevin.tian@intel.com> Cc: Lars Persson <lars.persson@axis.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Marco Elver <elver@google.com> Cc: "Martin K. Petersen" <martin.petersen@oracle.com> Cc: Maxim Levitky <maximlevitsky@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Niklas Cassel <cassel@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Pavel Begunkov <asml.silence@gmail.com> Cc: Peter Xu <peterx@redhat.com> Cc: Robin Murohy <robin.murphy@arm.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Thomas Gleinxer <tglx@linutronix.de> Cc: Tvrtko Ursulin <tursulin@ursulin.net> Cc: Ulf Hansson <ulf.hansson@linaro.org> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Will Deacon <will@kernel.org> Cc: Yishai Hadas <yishaih@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.