Re: [PATCH v2] mm: memcg-v1: fix memsw and TCP failcnt accounting

[Tao Cui]

在 2026/8/11 11:08, Guopeng Zhang 写道:
> From: Guopeng Zhang <zhangguopeng@xxxxxxxxxx>
> 
> 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 or
> memcg->tcpmem.
> 
> Consequently, memory.memsw.failcnt remains zero when the memory+swap
> limit is hit. memory.kmem.tcp.limit_in_bytes still sets
> memcg->tcpmem.max, but TCP charge failures are not reflected in
> memory.kmem.tcp.failcnt.
> 
> Enable failcnt accounting for both v1 counters.
> 
> To reproduce memory.memsw.failcnt:
> 
>     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.
> 
> To reproduce memory.kmem.tcp.failcnt:
> 
>     CG=/sys/fs/cgroup/memory/tcpmem-test
>     LIMIT=65536
>     mkdir "$CG"
>     echo "$LIMIT" > "$CG/memory.kmem.tcp.limit_in_bytes"
> 
> Start a child process in the cgroup, create a TCP socket, and reserve
> 1 MiB of socket memory with SO_RESERVE_MEM. The reservation fails with
> ENOMEM.
> 
>     cat "$CG/memory.kmem.tcp.failcnt"
> 
> Without the patch, memory.kmem.tcp.failcnt is 0. With the patch,
> memory.kmem.tcp.failcnt is greater than 0.
> 
> Closes: https://sashiko.dev/#/patchset/20260810074247.52747-1-guopeng.zhang@xxxxxxxxx?part=1
> Fixes: 0e2759afcaf9 ("page_counter: track failcnt only for legacy cgroups")
> Cc: stable@xxxxxxxxxxxxxxx
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Signed-off-by: Guopeng Zhang <zhangguopeng@xxxxxxxxxx>
> ---
> Changes in v2:
> - Enable failcnt tracking for tcpmem as suggested by Johannes Weiner.
> - Add the memory.kmem.tcp.failcnt reproducer and test result.
> - Update the subject and changelog to cover both counters.
> - Add Cc: stable@xxxxxxxxxxxxxxx and the received Acked-by tags.
> 
> Link to v1: https://lore.kernel.org/r/20260810074247.52747-1-guopeng.zhang@xxxxxxxxx
> 
>  mm/memcontrol.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 70806373d5a9..17da1f43b7d3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4235,9 +4235,11 @@ 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);
> +		memcg->tcpmem.track_failcnt = !memcg_on_dfl;
>  #endif
>  	} else {
>  		init_memcg_stats();
Reviewed-by: Tao Cui <cuitao@xxxxxxxxxx>