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

[Guopeng Zhang <guopeng.zhang@linux.dev>]

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