[PATCH bpf-next v1 2/5] cgroup: bpf: add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs

[Yosry Ahmed <yosryahmed@google.com>]

Add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs to bpf
tracing programs. bpf programs that make use of rstat can use these
functions to inform rstat when they update stats for a cgroup, and when
they need to flush the stats.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 kernel/cgroup/rstat.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index e7a88d2600bd..a16a851bc0a1 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -3,6 +3,11 @@
 
 #include <linux/sched/cputime.h>
 
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/btf_ids.h>
+
+
 static DEFINE_SPINLOCK(cgroup_rstat_lock);
 static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock);
 
@@ -141,7 +146,12 @@ 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 */
+/*
+ * A hook for bpf stat collectors to attach to and flush their stats.
+ * Together with providing bpf kfuncs for cgroup_rstat_updated() and
+ * cgroup_rstat_flush(), this enables a complete workflow where bpf progs that
+ * collect cgroup stats can integrate with rstat for efficient flushing.
+ */
 __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
 				     struct cgroup *parent, int cpu)
 {
@@ -476,3 +486,26 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq)
 		   "system_usec %llu\n",
 		   usage, utime, stime);
 }
+
+/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
+BTF_SET_START(bpf_rstat_check_kfunc_ids)
+BTF_ID(func, cgroup_rstat_updated)
+BTF_ID(func, cgroup_rstat_flush)
+BTF_SET_END(bpf_rstat_check_kfunc_ids)
+
+BTF_SET_START(bpf_rstat_sleepable_kfunc_ids)
+BTF_ID(func, cgroup_rstat_flush)
+BTF_SET_END(bpf_rstat_sleepable_kfunc_ids)
+
+static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {
+	.owner		= THIS_MODULE,
+	.check_set	= &bpf_rstat_check_kfunc_ids,
+	.sleepable_set	= &bpf_rstat_sleepable_kfunc_ids,
+};
+
+static int __init bpf_rstat_kfunc_init(void)
+{
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
+					 &bpf_rstat_kfunc_set);
+}
+late_initcall(bpf_rstat_kfunc_init);
-- 
2.36.1.124.g0e6072fb45-goog