The patch titled
Subject: mm: shmem: fix incorrect index alignment for within_size policy
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-shmem-fix-incorrect-index-alignment-for-within_size-policy.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-fix-incorrect-index-alignment-for-within_size-policy.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: shmem: fix incorrect index alignment for within_size policy
Date: Thu, 19 Dec 2024 15:30:08 +0800
With enabling the shmem per-size within_size policy, using an incorrect
'order' size to round_up() the index can lead to incorrect i_size checks,
resulting in an inappropriate large orders being returned.
Changing to use '1 << order' to round_up() the index to fix this issue.
Additionally, adding an 'aligned_index' variable to avoid affecting the
index checks.
Link: https://lkml.kernel.org/r/77d8ef76a7d3d646e9225e9af88a76549a68aab1.1734593154.git.baolin.wang@xxxxxxxxxxxxxxxxx
Fixes: e7a2ab7b3bb5 ("mm: shmem: add mTHP support for anonymous shmem")
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/shmem.c~mm-shmem-fix-incorrect-index-alignment-for-within_size-policy
+++ a/mm/shmem.c
@@ -1689,6 +1689,7 @@ unsigned long shmem_allowable_huge_order
unsigned long mask = READ_ONCE(huge_shmem_orders_always);
unsigned long within_size_orders = READ_ONCE(huge_shmem_orders_within_size);
unsigned long vm_flags = vma ? vma->vm_flags : 0;
+ pgoff_t aligned_index;
bool global_huge;
loff_t i_size;
int order;
@@ -1723,9 +1724,9 @@ unsigned long shmem_allowable_huge_order
/* Allow mTHP that will be fully within i_size. */
order = highest_order(within_size_orders);
while (within_size_orders) {
- index = round_up(index + 1, order);
+ aligned_index = round_up(index + 1, 1 << order);
i_size = round_up(i_size_read(inode), PAGE_SIZE);
- if (i_size >> PAGE_SHIFT >= index) {
+ if (i_size >> PAGE_SHIFT >= aligned_index) {
mask |= within_size_orders;
break;
}
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
docs-mm-fix-the-incorrect-filehugemapped-field.patch
mm-shmem-fix-incorrect-index-alignment-for-within_size-policy.patch
mm-shmem-fix-the-update-of-shmem_falloc-nr_unswapped.patch
mm-factor-out-the-order-calculation-into-a-new-helper.patch
mm-shmem-change-shmem_huge_global_enabled-to-return-huge-order-bitmap.patch
mm-shmem-add-large-folio-support-for-tmpfs.patch
mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs.patch
docs-tmpfs-drop-fadvise-from-the-documentation.patch
