The quilt patch titled Subject: mm/huge_memory: fix folio split check for anon folios in swapcache has been removed from the -mm tree. Its filename was mm-huge_memory-fix-folio-split-check-for-anon-folios-in-swapcache.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: Zi Yan ziy@nvidia.com Subject: mm/huge_memory: fix folio split check for anon folios in swapcache Date: Wed, 5 Nov 2025 11:29:10 -0500
Both uniform and non uniform split check missed the check to prevent splitting anon folios in swapcache to non-zero order.
Splitting anon folios in swapcache to non-zero order can cause data corruption since swapcache only support PMD order and order-0 entries. This can happen when one use split_huge_pages under debugfs to split anon folios in swapcache.
In-tree callers do not perform such an illegal operation. Only debugfs interface could trigger it. I will put adding a test case on my TODO list.
Fix the check.
Link: https://lkml.kernel.org/r/20251105162910.752266-1-ziy@nvidia.com Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-uniform) folio_split()") Signed-off-by: Zi Yan ziy@nvidia.com Reported-by: "David Hildenbrand (Red Hat)" david@kernel.org Closes: https://lore.kernel.org/all/dc0ecc2c-4089-484f-917f-920fdca4c898@kernel.org/ Acked-by: David Hildenbrand (Red Hat) david@kernel.org Cc: Baolin Wang baolin.wang@linux.alibaba.com Cc: Barry Song baohua@kernel.org Cc: Dev Jain dev.jain@arm.com Cc: Lance Yang lance.yang@linux.dev Cc: Liam Howlett liam.howlett@oracle.com Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Nico Pache npache@redhat.com Cc: Ryan Roberts ryan.roberts@arm.com Cc: Wei Yang richard.weiyang@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/huge_memory.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/huge_memory.c~mm-huge_memory-fix-folio-split-check-for-anon-folios-in-swapcache +++ a/mm/huge_memory.c @@ -3522,7 +3522,8 @@ bool non_uniform_split_supported(struct /* order-1 is not supported for anonymous THP. */ VM_WARN_ONCE(warns && new_order == 1, "Cannot split to order-1 folio"); - return new_order != 1; + if (new_order == 1) + return false; } else if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !mapping_large_folio_support(folio->mapping)) { /* @@ -3553,7 +3554,8 @@ bool uniform_split_supported(struct foli if (folio_test_anon(folio)) { VM_WARN_ONCE(warns && new_order == 1, "Cannot split to order-1 folio"); - return new_order != 1; + if (new_order == 1) + return false; } else if (new_order) { if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !mapping_large_folio_support(folio->mapping)) { _
Patches currently in -mm which might be from ziy@nvidia.com are
mm-huge_memory-add-split_huge_page_to_order.patch mm-memory-failure-improve-large-block-size-folio-handling.patch mm-huge_memory-fix-kernel-doc-comments-for-folio_split-and-related.patch mm-huge_memory-fix-kernel-doc-comments-for-folio_split-and-related-fix.patch mm-huge_memory-fix-kernel-doc-comments-for-folio_split-and-related-fix-2.patch migrate-optimise-alloc_migration_target-fix.patch