Re: [PATCH v2 17/33] mm: introduce and use linear_page_delta()
From: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Date: 2026-07-15 14:57:55
Also in:
damon, dri-devel, kvm, linux-arm-msm, linux-fsdevel, linux-iommu, linux-mm, linux-perf-users, linux-tegra, lkml, nvdimm
On 7/10/26 22:16, Lorenzo Stoakes wrote:
It's often useful to obtain the number of pages a given address lies at within a VMA. Add linear_page_delta() to determine this and update linear_page_index() to make use of it. Add comments to describe both linear_page_delta() and linear_page_index(). We refer the reader to the comment for vma_start_pgoff() so we don't duplicate information about the meaning of a VMA's page offset, which is also less likely to result in bitrot. No functional change intended. Reviewed-by: Ackerley Tng <redacted> Reviewed-by: Gregory Price <gourry@gourry.net> Reviewed-by: Pedro Falcato <pfalcato@suse.de> Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
quoted hunk ↗ jump to hunk
--- include/linux/pagemap.h | 33 +++++++++++++++++++++++++++++++-- 1 file changed, 31 insertions(+), 2 deletions(-)diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 2c3718d592d6..a950070b045f 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h@@ -1063,11 +1063,40 @@ static inline pgoff_t folio_pgoff(const struct folio *folio) return folio->index; } +/** + * linear_page_delta() - Determine the relative page offset of @address within + * @vma. + * @vma: The VMA in which @address resides. + * @address: The address whose relative page offset is required. + * + * The result is identical for both file-backed and anonymous mappings and + * simply determines how many pages @address lies from @vma->vm_start. + * + * Returns: The number of pages @address is offset by within @vma. + */ +static inline pgoff_t linear_page_delta(const struct vm_area_struct *vma, + const unsigned long address) +{ + return (address - vma->vm_start) >> PAGE_SHIFT; +} + +/** + * linear_page_index() - Determine the absolute page offset of @address within + * @vma. + * @vma: The VMA in which @address resides. + * @address: The address whose absolute page offset is required. + * + * See the comment for vma_start_pgoff() for a description of what the page + * offset signifies. + * + * Returns: The absolute page offset of @address within @vma. + */ static inline pgoff_t linear_page_index(const struct vm_area_struct *vma, const unsigned long address) { pgoff_t pgoff; - pgoff = (address - vma->vm_start) >> PAGE_SHIFT; + + pgoff = linear_page_delta(vma, address); pgoff += vma->vm_pgoff; return pgoff; }@@ -1219,7 +1248,7 @@ static inline vm_fault_t folio_lock_or_retry(struct folio *folio, void folio_wait_bit(struct folio *folio, int bit_nr); int folio_wait_bit_killable(struct folio *folio, int bit_nr); -/* +/* * Wait for a folio to be unlocked. * * This must be called with the caller "holding" the folio,