+ mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg-fix.patch added to mm-unstable branch

+ mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg-fix.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: kmem: fix split_page_memcg()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg-fix.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: kmem: fix split_page_memcg()
Date: Mon, 19 Aug 2024 16:04:15 +0800

split_page_memcg() does not care about the returned memcg for kmem
pages, so folio_memcg_charged() should be used, otherwise obj_cgroup_memcg
will complain about this.

Link: https://lkml.kernel.org/r/20240819080415.44964-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reported-by: syzbot+ef4ecf7b6bdc4157bfa4@syzkaller.appspotmail.com
Closes: https://lkml.kernel.org/r/0000000000006f7e4d0620042b96@google.com
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/mm/memcontrol.c~mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg-fix
+++ a/mm/memcontrol.c
@@ -3035,12 +3035,11 @@ void __memcg_slab_free_hook(struct kmem_
 void split_page_memcg(struct page *head, int old_order, int new_order)
 {
 	struct folio *folio = page_folio(head);
-	struct mem_cgroup *memcg = folio_memcg(folio);
 	int i;
 	unsigned int old_nr = 1 << old_order;
 	unsigned int new_nr = 1 << new_order;
 
-	if (mem_cgroup_disabled() || !memcg)
+	if (mem_cgroup_disabled() || !folio_memcg_charged(folio))
 		return;
 
 	for (i = new_nr; i < old_nr; i += new_nr)
@@ -3049,7 +3048,7 @@ void split_page_memcg(struct page *head,
 	if (folio_memcg_kmem(folio))
 		obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1);
 	else
-		css_get_many(&memcg->css, old_nr / new_nr - 1);
+		css_get_many(&folio_memcg(folio)->css, old_nr / new_nr - 1);
 }
 
 unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-kmem-remove-mem_cgroup_from_obj.patch
mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg.patch
mm-kmem-add-lockdep-assertion-to-obj_cgroup_memcg-fix.patch