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mm: percpu: fix incorrect size in pcpu_obj_full_size()

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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>
This commit is contained in:
Yafang Shao 2023-02-14 15:35:49 +00:00 committed by Andrew Morton
parent 44081c77e8
commit 2ef8ed7ddd
1 changed files with 4 additions and 2 deletions
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6
mm/percpu-internal.h
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@ -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(struct pcpu_chunk *chunk)
* @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;