[merged mm-hotfixes-stable] mm-shmem-fix-thp-allocation-and-fallback-loop.patch removed from -mm tree

[merged mm-hotfixes-stable] mm-shmem-fix-thp-allocation-and-fallback-loop.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/shmem: fix THP allocation and fallback loop
has been removed from the -mm tree.  Its filename was
     mm-shmem-fix-thp-allocation-and-fallback-loop.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Kairui Song <kasong@tencent.com>
Subject: mm/shmem: fix THP allocation and fallback loop
Date: Wed, 22 Oct 2025 18:57:19 +0800

The order check and fallback loop is updating the index value on every
loop.  This will cause the index to be wrongly aligned by a larger value
while the loop shrinks the order.

This may result in inserting and returning a folio of the wrong index and
cause data corruption with some userspace workloads [1].

[kasong@tencent.com: introduce a temporary variable to improve code]
  Link: https://lkml.kernel.org/r/20251023065913.36925-1-ryncsn@gmail.com
  Link: https://lore.kernel.org/linux-mm/CAMgjq7DqgAmj25nDUwwu1U2cSGSn8n4-Hqpgottedy0S6YYeUw@mail.gmail.com/ [1]
Link: https://lkml.kernel.org/r/20251022105719.18321-1-ryncsn@gmail.com
Link: https://lore.kernel.org/linux-mm/CAMgjq7DqgAmj25nDUwwu1U2cSGSn8n4-Hqpgottedy0S6YYeUw@mail.gmail.com/ [1]
Fixes: e7a2ab7b3bb5 ("mm: shmem: add mTHP support for anonymous shmem")
Closes: https://lore.kernel.org/linux-mm/CAMgjq7DqgAmj25nDUwwu1U2cSGSn8n4-Hqpgottedy0S6YYeUw@mail.gmail.com/
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/shmem.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/mm/shmem.c~mm-shmem-fix-thp-allocation-and-fallback-loop
+++ a/mm/shmem.c
@@ -1882,6 +1882,7 @@ static struct folio *shmem_alloc_and_add
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	unsigned long suitable_orders = 0;
 	struct folio *folio = NULL;
+	pgoff_t aligned_index;
 	long pages;
 	int error, order;
 
@@ -1895,10 +1896,12 @@ static struct folio *shmem_alloc_and_add
 		order = highest_order(suitable_orders);
 		while (suitable_orders) {
 			pages = 1UL << order;
-			index = round_down(index, pages);
-			folio = shmem_alloc_folio(gfp, order, info, index);
-			if (folio)
+			aligned_index = round_down(index, pages);
+			folio = shmem_alloc_folio(gfp, order, info, aligned_index);
+			if (folio) {
+				index = aligned_index;
 				goto allocated;
+			}
 
 			if (pages == HPAGE_PMD_NR)
 				count_vm_event(THP_FILE_FALLBACK);
_

Patches currently in -mm which might be from kasong@tencent.com are

mm-swap-do-not-perform-synchronous-discard-during-allocation.patch
mm-swap-rename-helper-for-setup-bad-slots.patch
mm-swap-cleanup-swap-entry-allocation-parameter.patch
mm-migrate-swap-drop-usage-of-folio_index.patch
mm-swap-remove-redundant-argument-for-isolating-a-cluster.patch
revert-mm-swap-avoid-redundant-swap-device-pinning.patch