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/ Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> Reviewed-by: Roman Gushchin <roman.gushchin@xxxxxxxxx> Acked-by: Dennis Zhou <dennis@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Vasily Averin <vvs@xxxxxxxxxx> --- mm/percpu-internal.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- v1->v2: improve the commit log and comments (Andrew) diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index 70b1ea2..f9847c1 100644 --- a/mm/percpu-internal.h +++ b/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(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; -- 1.8.3.1
