[merged mm-stable] mm-huge_memory-add-page-private-check-back-in-__split_folio_to_order.patch removed from -mm tree

[merged mm-stable] mm-huge_memory-add-page-private-check-back-in-__split_folio_to_order.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/huge_memory: add page->private check back in __split_folio_to_order()
has been removed from the -mm tree.  Its filename was
     mm-huge_memory-add-page-private-check-back-in-__split_folio_to_order.patch

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

------------------------------------------------------
From: Zi Yan <ziy@nvidia.com>
Subject: mm/huge_memory: add page->private check back in __split_folio_to_order()
Date: Thu, 09 Jul 2026 14:06:03 -0400

page->private should not be set in tail pages.  Commit 4265d67e405a
("mm/migrate_device: add THP splitting during migration") removed a
DEBUG_VM check without a proper reason[1].  Add it back.

Link: https://lore.kernel.org/all/13f3fcda-7328-4aa5-afc6-75a294a82b2a@nvidia.com/ [1]
Link: https://lore.kernel.org/20260709-keep-subpage-private-zero-at-free-v3-3-7e4fe155f5b9@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/mm/huge_memory.c~mm-huge_memory-add-page-private-check-back-in-__split_folio_to_order
+++ a/mm/huge_memory.c
@@ -3591,6 +3591,13 @@ static void __split_folio_to_order(struc
 		new_folio->mapping = folio->mapping;
 		new_folio->index = folio->index + i;
 
+		/*
+		 * page->private should not be set in tail pages. Warn once
+		 * if private is unexpectedly set. Do it before swap.val assignment
+		 * since private overlaps with swap.val.
+		 */
+		VM_WARN_ON_ONCE_PAGE(new_folio->private, new_head);
+
 		if (folio_test_swapcache(folio))
 			new_folio->swap.val = folio->swap.val + i;
 
_

Patches currently in -mm which might be from ziy@nvidia.com are

mm-huge_memory-use-folios-memcg-inside-__folio_split.patch
xarray-honor-xa_flags_account-in-xas_split_alloc.patch