[PATCH v2 2/3] cgroup/rstat: Cleanup cpu.stat once for all

[Abel Wu <wuyun.abel@bytedance.com>]

There were efforts like b824766504e4 ("cgroup/rstat: add force idle show helper")
to escape from #ifdef hells, and there could be new stats coming out in
the future, let's clean it up once for all.

Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
---
 kernel/cgroup/rstat.c | 47 ++++++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index c2784c317cdd..dc6acab00d69 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -599,21 +599,39 @@ static void root_cgroup_cputime(struct cgroup_base_stat *bstat)
 	}
 }
 
+static struct bstat_entry {
+	const char	*name;
+	const int	offset;
+} bstats[] = {
+#define BSTAT_ENTRY(name, field)	\
+	{ name, offsetof(struct cgroup_base_stat, field) }
+	BSTAT_ENTRY("usage_usec",	cputime.sum_exec_runtime),
+	BSTAT_ENTRY("user_usec",	cputime.utime),
+	BSTAT_ENTRY("system_usec",	cputime.stime),
+	BSTAT_ENTRY("nice_usec",	ntime),
+#ifdef CONFIG_SCHED_CORE
+	BSTAT_ENTRY("core_sched.force_idle_usec", forceidle_sum),
+#endif
+	{ NULL } /* must be at end */
+#undef BSTAT_ENTRY
+};
 
-static void cgroup_force_idle_show(struct seq_file *seq, struct cgroup_base_stat *bstat)
+static void cgroup_bstat_entry_show(struct seq_file *seq,
+				    struct cgroup_base_stat *bstat,
+				    struct bstat_entry *entry)
 {
-#ifdef CONFIG_SCHED_CORE
-	u64 forceidle_time = bstat->forceidle_sum;
+	u64 *val;
 
-	do_div(forceidle_time, NSEC_PER_USEC);
-	seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time);
-#endif
+	val = (void *)bstat + entry->offset;
+	do_div(*val, NSEC_PER_USEC);
+	seq_printf(seq, "%s %llu\n", entry->name, *val);
 }
 
 void cgroup_base_stat_cputime_show(struct seq_file *seq)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
 	struct cgroup_base_stat bstat;
+	struct bstat_entry *e;
 
 	if (cgroup_parent(cgrp)) {
 		cgroup_rstat_flush_hold(cgrp);
@@ -625,21 +643,8 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq)
 		root_cgroup_cputime(&bstat);
 	}
 
-	do_div(bstat.cputime.sum_exec_runtime, NSEC_PER_USEC);
-	do_div(bstat.cputime.utime, NSEC_PER_USEC);
-	do_div(bstat.cputime.stime, NSEC_PER_USEC);
-	do_div(bstat.ntime, NSEC_PER_USEC);
-
-	seq_printf(seq, "usage_usec %llu\n"
-			"user_usec %llu\n"
-			"system_usec %llu\n"
-			"nice_usec %llu\n",
-			bstat.cputime.sum_exec_runtime,
-			bstat.cputime.utime,
-			bstat.cputime.stime,
-			bstat.ntime);
-
-	cgroup_force_idle_show(seq, &bstat);
+	for (e = bstats; e->name; e++)
+		cgroup_bstat_entry_show(seq, &bstat, e);
 }
 
 /* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
-- 
2.37.3