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Patch series "mm: make VMA page offset handling more consistent", v2. This series performs a series of cleanups and improvements around how the vma->vm_pgoff field is used. Folios belonging to file-backed mappings are simply indexed by the page offset within the file they map (excepting pfnmap and driver mappings which sometimes do things different). However, anonymous folios belonging to pure anonymous mappings are indexed by their "virtual" page offset, which is equal to addr >> PAGE_SHIFT at the time at which the VMA was first faulted in. The page offset of a VMA is stored in vma->vm_pgoff and indicates the page offset of the start of the VMA range, whether it be file-backed or anonymous. The work here both cleans up how we reference this field, as well as laying the foundations for a future series which addresses the inconsistency of CoW'd folios in MAP_PRIVATE-file backed mappings, which are indexed as if they were file-backed but behave as if they were anonymous. This future series will make it such that all anonymous folios are indexed by virtual page offset whether belonging to VMAs who satisfy vma_is_anonymous() or MAP_PRIVATE-mapped file-backed mappings. This series: * Exposes vma_start_pgoff() and updates the kernel to use it consistently. * Adds and uses the useful vma_end_pgoff() helper. * Parameterises the file-backed mapping helpers vma_interval_tree_*() by address_space rather than rb_root_cached. * Renames: the misleadingly-named vma_interval_tree_*() helpers to mapping_rmap_tree_*() to be consistent with the renamed anon_rmap_tree_*(). * Parameterises anon_rmap_tree_*() by anon_vma. * Moves mm/interval_tree.c to the rmap section. * Adds vmg_*() helpers for page offset. * Clarifies the confusing vmg_adjust_set_range() function. * Introduces linear_page_delta() to provide relative pgoff within a VMA. * Replaces open-coded versions of linear_page_delta() and linear_page_index() with invocations of these functions. * Introduces and uses vma_assert_can_modify() to account for whether a VMA can be modified (detached or write locked). * Adds and uses vma_[add,sub]_pgoff() to adjust VMA page offset. * Moves __install_special_mapping() to vma.c. * Makes vma_set_range() static and internal to vma.c. * Introduces and makes use of vma_set_pgoff(). * Fixes incorrect vma.h header inclusion. * Defaults VMA userland tests to 64-bit vma flags size. * Updates VMA userland tests to give better output on failure. * Various smaller cleanups. * Updated the vma_set_pgoff() assert to account for MAP_PRIVATE /dev/zero correctly. This patch (of 33): vma_last_pgoff() already lives there, so it's a bit odd to keep vma_start_pgoff() in mm/interval_tree.c. Move them together. These each return unsigned long, which pgoff_t is typedef'd to. Make this consistent and have these functions return pgoff_t instead. Additionally, express vma_last_pgoff() in terms of vma_start_pgoff(), since we wrap the vma->vm_pgoff access, we may as well use it here. Also while we're here, const-ify the VMA and cleanup a bit. Also update the VMA userland tests to reflect the change. No functional change intended. Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-0-2a5aa403d977@kernel.org Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-1-2a5aa403d977@kernel.org Signed-off-by: Lorenzo Stoakes <ljs@kernel.org> Reviewed-by: Gregory Price <gourry@gourry.net> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Reviewed-by: Pedro Falcato <pfalcato@suse.de> Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org> Reviewed-by: Liam R. Howlett (Oracle) <liam@infradead.org> Reviewed-by: Zi Yan <ziy@nvidia.com> Cc: Ackerley Tng <ackerleytng@google.com> Cc: Kai Huang <kai.huang@intel.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: SJ Park <sj@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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