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mm: shmem: fix incorrect index alignment for within_size policy

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commit d0e6983a6d1719738cf8d13982a68094f0a1872a upstream.

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@linux.alibaba.com
Fixes: e7a2ab7b3b ("mm: shmem: add mTHP support for anonymous shmem")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Baolin Wang
2024-12-19 15:30:08 +08:00
committed by Greg Kroah-Hartman
parent cabacb18a4
commit 9e4c11d4cc
1 changed files with 3 additions and 2 deletions
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5
mm/shmem.c
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@@ -1664,6 +1664,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
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;
@@ -1698,9 +1699,9 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
/* 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;
}