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mm/vma: update vmg_adjust_set_range() to offset pgoff instead

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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 <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Ackerley Tng <ackerleytng@google.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
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>
Cc: Liam R. Howlett (Oracle) <liam@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2026-07-10 21:17:08 +01:00
committed by Andrew Morton
parent 6387563e6e
commit ce4ec991da
1 changed files with 4 additions and 11 deletions
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15
mm/vma.c
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@@ -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);
}
/*