[PATCH v4 1/3] misc_cgroup: introduce misc.events to count failures

[brookxu <brookxu.cn@xxxxxxxxx>]

From: Chunguang Xu <brookxu@xxxxxxxxxxx>

Introduce misc.events to make it easier for us to understand
the pressure of resources. Currently only the 'max' event is
implemented, which indicates the times the resource is about
to exceeds the max limit.

Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx>
Reviewed-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx>
---
v3: remove misc.events.local
v2: remove cgroup v1 files.

 include/linux/misc_cgroup.h |  5 +++++
 kernel/cgroup/misc.c        | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
index da2367e..091f2d2 100644
--- a/include/linux/misc_cgroup.h
+++ b/include/linux/misc_cgroup.h
@@ -36,6 +36,7 @@ enum misc_res_type {
 struct misc_res {
 	unsigned long max;
 	atomic_long_t usage;
+	atomic_long_t events;
 	bool failed;
 };
 
@@ -46,6 +47,10 @@ struct misc_res {
  */
 struct misc_cg {
 	struct cgroup_subsys_state css;
+
+	/* misc.events */
+	struct cgroup_file events_file;
+
 	struct misc_res res[MISC_CG_RES_TYPES];
 };
 
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
index ec02d96..4b2b492 100644
--- a/kernel/cgroup/misc.c
+++ b/kernel/cgroup/misc.c
@@ -171,6 +171,11 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
 	return 0;
 
 err_charge:
+	for (j = i; j; j = parent_misc(j)) {
+		atomic_long_inc(&j->res[type].events);
+		cgroup_file_notify(&j->events_file);
+	}
+
 	for (j = cg; j != i; j = parent_misc(j))
 		misc_cg_cancel_charge(type, j, amount);
 	misc_cg_cancel_charge(type, i, amount);
@@ -335,6 +340,19 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 	return 0;
 }
 
+static int misc_events_show(struct seq_file *sf, void *v)
+{
+	struct misc_cg *cg = css_misc(seq_css(sf));
+	unsigned long events, i;
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		events = atomic_long_read(&cg->res[i].events);
+		if (READ_ONCE(misc_res_capacity[i]) || events)
+			seq_printf(sf, "%s.max %lu\n", misc_res_name[i], events);
+	}
+	return 0;
+}
+
 /* Misc cgroup interface files */
 static struct cftype misc_cg_files[] = {
 	{
@@ -353,6 +371,12 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 		.seq_show = misc_cg_capacity_show,
 		.flags = CFTYPE_ONLY_ON_ROOT,
 	},
+	{
+		.name = "events",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.file_offset = offsetof(struct misc_cg, events_file),
+		.seq_show = misc_events_show,
+	},
 	{}
 };
 
-- 
1.8.3.1