This is based on mm-unstable.
I will only CC non-MM folks on the cover letter and the respective patch to not flood too many inboxes (the lists receive all patches).
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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 #21 : disallow CMA allocations of non-contiguous pages Patch #22 -> #32 : sanity+check + remove nth_page() usage within SG entry Patch #33 : sanity-check + remove nth_page() usage in unpin_user_page_range_dirty_lock() Patch #34 : remove nth_page() in kfence Patch #35 : adjust stale comment regarding nth_page Patch #36 : mm: remove nth_page()
A lot of this is inspired from the discussion at [1] between Linus, Jason and me, so cudos to them.
[1] https://lore.kernel.org/all/CAHk-=wiCYfNp4AJLBORU-c7ZyRBUp66W2-Et6cdQ4REx-Gy...
RFC -> v1: * "wireguard: selftests: remove CONFIG_SPARSEMEM_VMEMMAP=y from qemu kernel config" -> Mention that it was never really relevant for the test * "mm/mm_init: make memmap_init_compound() look more like prep_compound_page()" -> Mention the setup of page links * "mm: limit folio/compound page sizes in problematic kernel configs" -> Improve comment for PUD handling, mentioning hugetlb and dax * "mm: simplify folio_page() and folio_page_idx()" -> Call variable "n" * "mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap()" -> Keep __init_single_page() and refer to the usage of memblock_reserved_mark_noinit() * "fs: hugetlbfs: cleanup folio in adjust_range_hwpoison()" * "fs: hugetlbfs: remove nth_page() usage within folio in adjust_range_hwpoison()" -> Separate nth_page() removal from cleanups -> Further improve cleanups * "io_uring/zcrx: remove nth_page() usage within folio" -> Keep the io_copy_cache for now and limit to nth_page() removal * "mm/gup: drop nth_page() usage within folio when recording subpages" -> Cleanup record_subpages as bit * "mm/cma: refuse handing out non-contiguous page ranges" -> Replace another instance of "pfn_to_page(pfn)" where we already have the page * "scatterlist: disallow non-contigous page ranges in a single SG entry" -> We have to EXPORT the symbol. I thought about moving it to mm_inline.h, but I really don't want to include that in include/linux/scatterlist.h * "ata: libata-eh: drop nth_page() usage within SG entry" * "mspro_block: drop nth_page() usage within SG entry" * "memstick: drop nth_page() usage within SG entry" * "mmc: drop nth_page() usage within SG entry" -> Keep PAGE_SHIFT * "scsi: scsi_lib: drop nth_page() usage within SG entry" * "scsi: sg: drop nth_page() usage within SG entry" -> Split patches, Keep PAGE_SHIFT * "crypto: remove nth_page() usage within SG entry" -> Keep PAGE_SHIFT * "kfence: drop nth_page() usage" -> Keep modifying i and use "start_pfn" only instead
Cc: Andrew Morton akpm@linux-foundation.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Jason Gunthorpe jgg@nvidia.com Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: "Liam R. Howlett" Liam.Howlett@oracle.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Mike Rapoport rppt@kernel.org Cc: Suren Baghdasaryan surenb@google.com Cc: Michal Hocko mhocko@suse.com Cc: Jens Axboe axboe@kernel.dk Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: Robin Murphy robin.murphy@arm.com Cc: John Hubbard jhubbard@nvidia.com Cc: Peter Xu peterx@redhat.com Cc: Alexander Potapenko glider@google.com Cc: Marco Elver elver@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Brendan Jackman jackmanb@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Zi Yan ziy@nvidia.com Cc: Dennis Zhou dennis@kernel.org Cc: Tejun Heo tj@kernel.org Cc: Christoph Lameter cl@gentwo.org Cc: Muchun Song muchun.song@linux.dev Cc: Oscar Salvador osalvador@suse.de Cc: x86@kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mips@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linux-crypto@vger.kernel.org Cc: linux-ide@vger.kernel.org Cc: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org Cc: linux-mmc@vger.kernel.org Cc: linux-arm-kernel@axis.com Cc: linux-scsi@vger.kernel.org Cc: kvm@vger.kernel.org Cc: virtualization@lists.linux.dev Cc: linux-mm@kvack.org Cc: io-uring@vger.kernel.org Cc: iommu@lists.linux.dev Cc: kasan-dev@googlegroups.com Cc: wireguard@lists.zx2c4.com Cc: netdev@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: linux-riscv@lists.infradead.org
David Hildenbrand (36): mm: stop making SPARSEMEM_VMEMMAP user-selectable arm64: Kconfig: drop superfluous "select SPARSEMEM_VMEMMAP" s390/Kconfig: drop superfluous "select SPARSEMEM_VMEMMAP" x86/Kconfig: drop superfluous "select SPARSEMEM_VMEMMAP" wireguard: selftests: remove CONFIG_SPARSEMEM_VMEMMAP=y from qemu kernel config mm/page_alloc: reject unreasonable folio/compound page sizes in alloc_contig_range_noprof() mm/memremap: reject unreasonable folio/compound page sizes in memremap_pages() mm/hugetlb: check for unreasonable folio sizes when registering hstate mm/mm_init: make memmap_init_compound() look more like prep_compound_page() mm: sanity-check maximum folio size in folio_set_order() mm: limit folio/compound page sizes in problematic kernel configs mm: simplify folio_page() and folio_page_idx() mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap() mm/mm/percpu-km: drop nth_page() usage within single allocation fs: hugetlbfs: remove nth_page() usage within folio in adjust_range_hwpoison() fs: hugetlbfs: cleanup folio in adjust_range_hwpoison() mm/pagewalk: drop nth_page() usage within folio in folio_walk_start() mm/gup: drop nth_page() usage within folio when recording subpages io_uring/zcrx: remove nth_page() usage within folio mips: mm: convert __flush_dcache_pages() to __flush_dcache_folio_pages() mm/cma: refuse handing out non-contiguous page ranges dma-remap: drop nth_page() in dma_common_contiguous_remap() scatterlist: disallow non-contigous page ranges in a single SG entry ata: libata-eh: drop nth_page() usage within SG entry drm/i915/gem: drop nth_page() usage within SG entry mspro_block: drop nth_page() usage within SG entry memstick: drop nth_page() usage within SG entry mmc: drop nth_page() usage within SG entry scsi: scsi_lib: drop nth_page() usage within SG entry scsi: sg: drop nth_page() usage within SG entry vfio/pci: drop nth_page() usage within SG entry crypto: remove nth_page() usage within SG entry mm/gup: drop nth_page() usage in unpin_user_page_range_dirty_lock() kfence: drop nth_page() usage block: update comment of "struct bio_vec" regarding nth_page() mm: remove nth_page()
arch/arm64/Kconfig | 1 - arch/mips/include/asm/cacheflush.h | 11 +++-- arch/mips/mm/cache.c | 8 ++-- arch/s390/Kconfig | 1 - arch/x86/Kconfig | 1 - crypto/ahash.c | 4 +- crypto/scompress.c | 8 ++-- drivers/ata/libata-sff.c | 6 +-- drivers/gpu/drm/i915/gem/i915_gem_pages.c | 2 +- drivers/memstick/core/mspro_block.c | 3 +- drivers/memstick/host/jmb38x_ms.c | 3 +- drivers/memstick/host/tifm_ms.c | 3 +- drivers/mmc/host/tifm_sd.c | 4 +- drivers/mmc/host/usdhi6rol0.c | 4 +- drivers/scsi/scsi_lib.c | 3 +- drivers/scsi/sg.c | 3 +- drivers/vfio/pci/pds/lm.c | 3 +- drivers/vfio/pci/virtio/migrate.c | 3 +- fs/hugetlbfs/inode.c | 33 +++++-------- include/crypto/scatterwalk.h | 4 +- include/linux/bvec.h | 7 +-- include/linux/mm.h | 48 +++++++++++++++---- include/linux/page-flags.h | 5 +- include/linux/scatterlist.h | 3 +- io_uring/zcrx.c | 4 +- kernel/dma/remap.c | 2 +- mm/Kconfig | 3 +- mm/cma.c | 39 +++++++++------ mm/gup.c | 14 ++++-- mm/hugetlb.c | 22 +++++---- mm/internal.h | 1 + mm/kfence/core.c | 12 +++-- mm/memremap.c | 3 ++ mm/mm_init.c | 15 +++--- mm/page_alloc.c | 5 +- mm/pagewalk.c | 2 +- mm/percpu-km.c | 2 +- mm/util.c | 34 +++++++++++++ tools/testing/scatterlist/linux/mm.h | 1 - .../selftests/wireguard/qemu/kernel.config | 1 - 40 files changed, 202 insertions(+), 129 deletions(-)
base-commit: efa7612003b44c220551fd02466bfbad5180fc83