[PATCH] mm: memcg-v1: fix memory.memsw.failcnt accounting

[PATCH] mm: memcg-v1: fix memory.memsw.failcnt accounting

[Guopeng Zhang]

From: Guopeng Zhang <zhangguopeng@kylinos.cn>

Commit 0e2759afcaf9 ("page_counter: track failcnt only for legacy
cgroups") made failcnt accounting conditional on track_failcnt. It
enabled the flag for memcg->memory, but not for memcg->memsw.

Consequently, memory.memsw.failcnt remains zero when the memory+swap
limit is hit. Enable failcnt accounting for the v1 memsw counter.

Reproducer:

    CG=/sys/fs/cgroup/memory/memsw-test
    LIMIT=33554432
    mkdir "$CG"
    echo "$LIMIT" > "$CG/memory.limit_in_bytes"
    echo "$LIMIT" > "$CG/memory.memsw.limit_in_bytes"

Start a child process in the cgroup and make it allocate and touch 96 MiB
of memory, causing a memcg OOM.

    cat "$CG/memory.memsw.failcnt"

Without the patch, memory.memsw.failcnt is 0. With the patch,
memory.memsw.failcnt is greater than 0.

Fixes: 0e2759afcaf9 ("page_counter: track failcnt only for legacy cgroups")
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
---
 mm/memcontrol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6939a4fbb991..4ffe5b3733d9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4235,6 +4235,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 #ifdef CONFIG_MEMCG_V1
 		WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
 		memcg->memory.track_failcnt = !memcg_on_dfl;
+		memcg->memsw.track_failcnt = !memcg_on_dfl;
 		WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
 		page_counter_init(&memcg->kmem, &parent->kmem, false);
 		page_counter_init(&memcg->tcpmem, &parent->tcpmem, false);
-- 
2.43.0

Re: [PATCH] mm: memcg-v1: fix memory.memsw.failcnt accounting

[Michal Hocko]

On Mon 10-08-26 15:42:47, Guopeng Zhang wrote:
> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
> 
> Commit 0e2759afcaf9 ("page_counter: track failcnt only for legacy
> cgroups") made failcnt accounting conditional on track_failcnt. It
> enabled the flag for memcg->memory, but not for memcg->memsw.
> 
> Consequently, memory.memsw.failcnt remains zero when the memory+swap
> limit is hit. Enable failcnt accounting for the v1 memsw counter.
> 
> Reproducer:
> 
>     CG=/sys/fs/cgroup/memory/memsw-test
>     LIMIT=33554432
>     mkdir "$CG"
>     echo "$LIMIT" > "$CG/memory.limit_in_bytes"
>     echo "$LIMIT" > "$CG/memory.memsw.limit_in_bytes"
> 
> Start a child process in the cgroup and make it allocate and touch 96 MiB
> of memory, causing a memcg OOM.
> 
>     cat "$CG/memory.memsw.failcnt"
> 
> Without the patch, memory.memsw.failcnt is 0. With the patch,
> memory.memsw.failcnt is greater than 0.
> 
> Fixes: 0e2759afcaf9 ("page_counter: track failcnt only for legacy cgroups")
> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>

Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!

> ---
>  mm/memcontrol.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6939a4fbb991..4ffe5b3733d9 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4235,6 +4235,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
>  #ifdef CONFIG_MEMCG_V1
>  		WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
>  		memcg->memory.track_failcnt = !memcg_on_dfl;
> +		memcg->memsw.track_failcnt = !memcg_on_dfl;
>  		WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
>  		page_counter_init(&memcg->kmem, &parent->kmem, false);
>  		page_counter_init(&memcg->tcpmem, &parent->tcpmem, false);
> -- 
> 2.43.0

-- 
Michal Hocko
SUSE Labs