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From:   Abel Wu <wuyun.abel@bytedance.com>
To:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Ahern <dsahern@kernel.org>,
        Yosry Ahmed <yosryahmed@google.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Yu Zhao <yuzhao@google.com>,
        Abel Wu <wuyun.abel@bytedance.com>,
        Kuniyuki Iwashima <kuniyu@amazon.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Martin KaFai Lau <martin.lau@kernel.org>,
        Alexander Mikhalitsyn <alexander@mihalicyn.com>,
        Breno Leitao <leitao@debian.org>,
        David Howells <dhowells@redhat.com>,
        Jason Xing <kernelxing@tencent.com>,
        Xin Long <lucien.xin@gmail.com>
Cc:     Michal Hocko <mhocko@suse.com>,
        linux-kernel@vger.kernel.org (open list),
        netdev@vger.kernel.org (open list:NETWORKING [GENERAL]),
        cgroups@vger.kernel.org (open list:CONTROL GROUP - MEMORY RESOURCE
        CONTROLLER (MEMCG)),
        linux-mm@kvack.org (open list:CONTROL GROUP - MEMORY RESOURCE
        CONTROLLER (MEMCG))
Subject: [PATCH net-next 1/2] net-memcg: Scopify the indicators of sockmem pressure
Date:   Sun, 25 Jun 2023 22:28:10 +0800
Message-Id: <20230625142820.47185-1-wuyun.abel@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Now there are two indicators of socket memory pressure sit inside
struct mem_cgroup, socket_pressure and tcpmem_pressure.

When in legacy mode aka. cgroupv1, the socket memory is charged
into a separate counter memcg->tcpmem rather than ->memory, so
the reclaim pressure of the memcg has nothing to do with socket's
pressure at all. While for default mode, the ->tcpmem is simply
not used.

So {socket,tcpmem}_pressure are only used in default/legacy mode
respectively. This patch fixes the pieces of code that make mixed
use of both.

Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
---
 include/linux/memcontrol.h | 4 ++--
 mm/vmpressure.c            | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 222d7370134c..9b1b536b4ec9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1743,8 +1743,8 @@ void mem_cgroup_sk_alloc(struct sock *sk);
 void mem_cgroup_sk_free(struct sock *sk);
 static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 {
-	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg->tcpmem_pressure)
-		return true;
+	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
+		return !!memcg->tcpmem_pressure;
 	do {
 		if (time_before(jiffies, READ_ONCE(memcg->socket_pressure)))
 			return true;
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index b52644771cc4..22c6689d9302 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -244,6 +244,14 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
 	if (mem_cgroup_disabled())
 		return;
 
+	/*
+	 * The in-kernel users only care about the reclaim efficiency
+	 * for this @memcg rather than the whole subtree, and there
+	 * isn't and won't be any in-kernel user in a legacy cgroup.
+	 */
+	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !tree)
+		return;
+
 	vmpr = memcg_to_vmpressure(memcg);
 
 	/*
-- 
2.37.3