linux-kernel - [PATCH bpf-next v2 5/7] mm: introduce BPF kfunc to access memory events

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Message-ID: <20251220041250.372179-6-roman.gushchin@linux.dev>
Date: Fri, 19 Dec 2025 20:12:48 -0800
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: bpf@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: JP Kobryn <inwardvessel@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Michal Hocko <mhocko@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>
Subject: [PATCH bpf-next v2 5/7] mm: introduce BPF kfunc to access memory events

From: JP Kobryn <inwardvessel@...il.com>

Introduce BPF kfunc to access memory events, e.g.:
MEMCG_LOW, MEMCG_MAX, MEMCG_OOM, MEMCG_OOM_KILL etc.

Signed-off-by: JP Kobryn <inwardvessel@...il.com>
Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
 mm/bpf_memcontrol.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c
index d84fe6f3ed43..858eb43766ce 100644
--- a/mm/bpf_memcontrol.c
+++ b/mm/bpf_memcontrol.c
@@ -103,6 +103,22 @@ __bpf_kfunc unsigned long bpf_mem_cgroup_usage(struct mem_cgroup *memcg)
 	return mem_cgroup_usage(memcg, false) * PAGE_SIZE;
 }
 
+/**
+ * bpf_mem_cgroup_memory_events - Read memory cgroup's memory event value
+ * @memcg: memory cgroup
+ * @event: memory event id
+ *
+ * Returns current memory event count.
+ */
+__bpf_kfunc unsigned long bpf_mem_cgroup_memory_events(struct mem_cgroup *memcg,
+						enum memcg_memory_event event)
+{
+	if (event >= MEMCG_NR_MEMORY_EVENTS)
+		return (unsigned long)-1;
+
+	return atomic_long_read(&memcg->memory_events[event]);
+}
+
 /**
  * bpf_mem_cgroup_page_state - Read memory cgroup's page state counter
  * @memcg: memory cgroup
@@ -137,6 +153,7 @@ BTF_ID_FLAGS(func, bpf_get_mem_cgroup, KF_TRUSTED_ARGS | KF_ACQUIRE | KF_RET_NUL
 BTF_ID_FLAGS(func, bpf_put_mem_cgroup, KF_TRUSTED_ARGS | KF_RELEASE)
 
 BTF_ID_FLAGS(func, bpf_mem_cgroup_vm_events, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_mem_cgroup_memory_events, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_mem_cgroup_usage, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_mem_cgroup_page_state, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_mem_cgroup_flush_stats, KF_TRUSTED_ARGS | KF_SLEEPABLE)
-- 
2.52.0