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mm/vma: minor cleanup of expand_[upwards, downwards]()

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Adjust the stack expansion functions expand_upwards() and
expand_downwards() such that they are expressed in terms of named constant
values, and make use of vma_start_pgoff().

This clearly documents that we are referencing the page offset of the start
of the VMA.

Additionally this cleans up the overflow check in expand_upwards().

No functional change intended.

Link: https://lore.kernel.org/20260710-b4-pre-scalable-cow-v2-16-2a5aa403d977@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 21:16:57 +01:00 committed by Andrew Morton
parent a30574d073
commit 68d307442b
1 changed files with 7 additions and 10 deletions
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17
mm/vma.c
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@ -3216,13 +3216,12 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
/* Somebody else might have raced and expanded it already */
if (address > vma->vm_end) {
unsigned long size, grow;
size = address - vma->vm_start;
grow = (address - vma->vm_end) >> PAGE_SHIFT;
const unsigned long size = address - vma->vm_start;
const unsigned long grow = (address - vma->vm_end) >> PAGE_SHIFT;
const pgoff_t pgoff = vma_start_pgoff(vma);
error = -ENOMEM;
if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
if (pgoff + (size >> PAGE_SHIFT) >= pgoff) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
if (vma_test(vma, VMA_LOCKED_BIT))
@ -3295,13 +3294,11 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address)
/* Somebody else might have raced and expanded it already */
if (address < vma->vm_start) {
unsigned long size, grow;
size = vma->vm_end - address;
grow = (vma->vm_start - address) >> PAGE_SHIFT;
const unsigned long size = vma->vm_end - address;
const unsigned long grow = (vma->vm_start - address) >> PAGE_SHIFT;
error = -ENOMEM;
if (grow <= vma->vm_pgoff) {
if (grow <= vma_start_pgoff(vma)) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
if (vma_test(vma, VMA_LOCKED_BIT))