From ce4ec991da01db884e96a96b2ac289b61f100d30 Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Fri, 10 Jul 2026 21:17:08 +0100 Subject: [PATCH] mm/vma: update vmg_adjust_set_range() to offset pgoff instead We are calculating the pgoff as an offset, since we have vma_add_pgoff() and vma_sub_pgoff() available, just offset this value directly and use __vma_set_range() for vma->vm_[start, end] values. We take care to update the range before offsetting the page offset, so the adjusted VMA's vm_start and vm_pgoff are mutually consistent at the point the page offset helpers operate - this matters once vma_set_pgoff() comes to assert invariants which relate the two. Doing so lays the foundation for future work which allows for use of virtual page offsets for MAP_PRIVATE-file backed mappings. No functional change intended. Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-27-2a5aa403d977@kernel.org Signed-off-by: Lorenzo Stoakes Reviewed-by: Pedro Falcato Reviewed-by: Gregory Price Reviewed-by: Vlastimil Babka (SUSE) Cc: Ackerley Tng Cc: David Hildenbrand (Arm) Cc: Kai Huang Cc: Marek Szyprowski Cc: SJ Park Cc: Thomas Zimmermann Cc: Liam R. Howlett (Oracle) Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/vma.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) diff --git a/mm/vma.c b/mm/vma.c index c75322d0ffc2..78af0e530066 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -714,9 +714,6 @@ void validate_mm(struct mm_struct *mm) */ static void vmg_adjust_set_range(struct vma_merge_struct *vmg) { - struct vm_area_struct *adjust; - pgoff_t pgoff; - if (vmg->__adjust_middle_start) { /* * vmg->start vmg->end @@ -735,8 +732,8 @@ static void vmg_adjust_set_range(struct vma_merge_struct *vmg) struct vm_area_struct *middle = vmg->middle; const unsigned long delta = vmg->end - middle->vm_start; - pgoff = vma_start_pgoff(middle) + (delta >> PAGE_SHIFT); - adjust = middle; + __vma_set_range(middle, vmg->end, middle->vm_end); + vma_add_pgoff(middle, delta >> PAGE_SHIFT); } else if (vmg->__adjust_next_start) { /* * Originally: @@ -764,13 +761,9 @@ static void vmg_adjust_set_range(struct vma_merge_struct *vmg) struct vm_area_struct *next = vmg->next; const unsigned long delta = next->vm_start - vmg->end; - pgoff = vma_start_pgoff(next) - (delta >> PAGE_SHIFT); - adjust = next; - } else { - return; + __vma_set_range(next, vmg->end, next->vm_end); + vma_sub_pgoff(next, delta >> PAGE_SHIFT); } - - vma_set_range(adjust, vmg->end, adjust->vm_end, pgoff); } /*