[PATCH bpf-next v1 1/5] cgroup: bpf: add a hook for bpf progs to attach to rstat flushing

[Yosry Ahmed <yosryahmed@google.com>]

Add an empty bpf_rstat_flush() hook that is called during rstat
flushing. bpf programs that make use of rstat and want to flush their
stats can attach to bpf_rstat_flush().

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 kernel/cgroup/rstat.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index 24b5c2ab5598..e7a88d2600bd 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -141,6 +141,12 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
 	return pos;
 }
 
+/* A hook for bpf stat collectors to attach to and flush their stats */
+__weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
+				     struct cgroup *parent, int cpu)
+{
+}
+
 /* see cgroup_rstat_flush() */
 static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
 	__releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
@@ -168,6 +174,7 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
 			struct cgroup_subsys_state *css;
 
 			cgroup_base_stat_flush(pos, cpu);
+			bpf_rstat_flush(pos, cgroup_parent(pos), cpu);
 
 			rcu_read_lock();
 			list_for_each_entry_rcu(css, &pos->rstat_css_list,
-- 
2.36.1.124.g0e6072fb45-goog