+ mm-percpu-fix-incorrect-size-in-pcpu_obj_full_size.patch added to mm-unstable branch

+ mm-percpu-fix-incorrect-size-in-pcpu_obj_full_size.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: percpu: fix incorrect size in pcpu_obj_full_size()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-percpu-fix-incorrect-size-in-pcpu_obj_full_size.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-percpu-fix-incorrect-size-in-pcpu_obj_full_size.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: Yafang Shao <laoar.shao@gmail.com>
Subject: mm: percpu: fix incorrect size in pcpu_obj_full_size()
Date: Tue, 14 Feb 2023 15:35:49 +0000

The extra space which is used to store the obj_cgroup membership is only
valid when kmemcg is enabled.  The kmemcg can be disabled via the kernel
parameter "cgroup.memory=nokmem" at boot time.  This helper is also used
in non-memcg code, for example the tracepoint, so we should fix it.

It was found by code review when I was implementing bpf memory usage[1]. 
No real issue happens in production environment.

[1]. https://lwn.net/Articles/921991/

Link: https://lkml.kernel.org/r/20230214153549.12291-1-laoar.shao@gmail.com
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Vasily Averin <vvs@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/percpu-internal.h~mm-percpu-fix-incorrect-size-in-pcpu_obj_full_size
+++ a/mm/percpu-internal.h
@@ -4,6 +4,7 @@
 
 #include <linux/types.h>
 #include <linux/percpu.h>
+#include <linux/memcontrol.h>
 
 /*
  * pcpu_block_md is the metadata block struct.
@@ -118,14 +119,15 @@ static inline int pcpu_chunk_map_bits(st
  * @size: size of area to allocate in bytes
  *
  * For each accounted object there is an extra space which is used to store
- * obj_cgroup membership. Charge it too.
+ * obj_cgroup membership if kmemcg is not disabled. Charge it too.
  */
 static inline size_t pcpu_obj_full_size(size_t size)
 {
 	size_t extra_size = 0;
 
 #ifdef CONFIG_MEMCG_KMEM
-	extra_size += size / PCPU_MIN_ALLOC_SIZE * sizeof(struct obj_cgroup *);
+	if (!mem_cgroup_kmem_disabled())
+		extra_size += size / PCPU_MIN_ALLOC_SIZE * sizeof(struct obj_cgroup *);
 #endif
 
 	return size * num_possible_cpus() + extra_size;
_

Patches currently in -mm which might be from laoar.shao@gmail.com are

mm-percpu-fix-incorrect-size-in-pcpu_obj_full_size.patch