+ mm-huge_memory-initialise-workingset-state-before-folio-split.patch added to mm-hotfixes-unstable branch

+ mm-huge_memory-initialise-workingset-state-before-folio-split.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/huge_memory: Initialise workingset state before folio split
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-huge_memory-initialise-workingset-state-before-folio-split.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-initialise-workingset-state-before-folio-split.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: Matt Fleming <mfleming@cloudflare.com>
Subject: mm/huge_memory: Initialise workingset state before folio split
Date: Sat, 25 Jul 2026 11:14:19 +0100

xas_try_split() adds __GFP_ACCOUNT for page-cache xa_nodes, but
__folio_split() leaves the xa_state's xa_lru unset.  That lets a live,
memcg-charged xa_node exist without being linked into the mapping's
shadow_nodes list_lru; when reclaim later walks the list_lru it trips
VM_WARN_ON(!css_is_dying()).

Use mapping_set_update() to install both the workingset update callback
and the shadow_nodes list_lru on the xa_state.

Link: https://lore.kernel.org/20260725101419.3938406-1-matt@readmodwrite.com
Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-uniform) folio_split()")
Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
Reported-by: syzbot+c5b060ce82921a2fd500@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c5b060ce82921a2fd500
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nico Pache <npache@redhat.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/huge_memory.c~mm-huge_memory-initialise-workingset-state-before-folio-split
+++ a/mm/huge_memory.c
@@ -4033,7 +4033,7 @@ static int __folio_split(struct folio *f
 		gfp_t gfp;
 
 		mapping = folio->mapping;
-		min_order = mapping_min_folio_order(folio->mapping);
+		min_order = mapping_min_folio_order(mapping);
 		if (new_order < min_order) {
 			ret = -EINVAL;
 			goto out;
@@ -4047,6 +4047,8 @@ static int __folio_split(struct folio *f
 			goto out;
 		}
 
+		mapping_set_update(&xas, mapping);
+
 		if (split_type == SPLIT_TYPE_UNIFORM) {
 			xas_set_order(&xas, folio->index, new_order);
 			xas_split_alloc(&xas, folio, old_order, gfp);
_

Patches currently in -mm which might be from mfleming@cloudflare.com are

mm-huge_memory-initialise-workingset-state-before-folio-split.patch