[PATCH bpf-next v1 5/6] mm: introduce BPF kfunc to access memory events

[Roman Gushchin <roman.gushchin@linux.dev>]

From: JP Kobryn <inwardvessel@gmail.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@gmail.com>
---
 mm/bpf_memcontrol.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c
index 4d9d7d909f6c..75076d682f75 100644
--- a/mm/bpf_memcontrol.c
+++ b/mm/bpf_memcontrol.c
@@ -99,6 +99,22 @@ __bpf_kfunc unsigned long bpf_mem_cgroup_usage(struct mem_cgroup *memcg)
 	return page_counter_read(&memcg->memory) * 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
@@ -133,6 +149,7 @@ 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