From 2e225799469c50f28c46ae2f7f511052696beca5 Mon Sep 17 00:00:00 2001
From: Kir Kolyshkin <kolyshkin@gmail.com>
Date: Fri, 3 Jul 2020 12:35:31 -0700
Subject: [PATCH] libct/cgroups/fs.GetStats: drop PathExists check

Half of controllers' GetStats just return nil, and most of the others
ignore ENOENT on files, so it will be cheaper to not check that the
path exists in the main GetStats method, offloading that to the
controllers.

Drop PathExists check from GetStats, add it to those controllers'
GetStats where it was missing.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
 libcontainer/cgroups/fs/cpuacct.go | 3 +++
 libcontainer/cgroups/fs/fs.go      | 2 +-
 libcontainer/cgroups/fs/hugetlb.go | 3 +++
 libcontainer/cgroups/fs/pids.go    | 3 +++
 4 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/libcontainer/cgroups/fs/cpuacct.go b/libcontainer/cgroups/fs/cpuacct.go
index bda34385..1797fb78 100644
--- a/libcontainer/cgroups/fs/cpuacct.go
+++ b/libcontainer/cgroups/fs/cpuacct.go
@@ -54,6 +54,9 @@ func (s *CpuacctGroup) Set(path string, cgroup *configs.Cgroup) error {
 }
 
 func (s *CpuacctGroup) GetStats(path string, stats *cgroups.Stats) error {
+	if !cgroups.PathExists(path) {
+		return nil
+	}
 	userModeUsage, kernelModeUsage, err := getCpuUsageBreakdown(path)
 	if err != nil {
 		return err
diff --git a/libcontainer/cgroups/fs/fs.go b/libcontainer/cgroups/fs/fs.go
index 8260c544..7ac0bdbe 100644
--- a/libcontainer/cgroups/fs/fs.go
+++ b/libcontainer/cgroups/fs/fs.go
@@ -250,7 +250,7 @@ func (m *manager) GetStats() (*cgroups.Stats, error) {
 	stats := cgroups.NewStats()
 	for name, path := range m.paths {
 		sys, err := m.getSubsystems().Get(name)
-		if err == errSubsystemDoesNotExist || !cgroups.PathExists(path) {
+		if err == errSubsystemDoesNotExist {
 			continue
 		}
 		if err := sys.GetStats(path, stats); err != nil {
diff --git a/libcontainer/cgroups/fs/hugetlb.go b/libcontainer/cgroups/fs/hugetlb.go
index 68f78462..a5e4c014 100644
--- a/libcontainer/cgroups/fs/hugetlb.go
+++ b/libcontainer/cgroups/fs/hugetlb.go
@@ -39,6 +39,9 @@ func (s *HugetlbGroup) Set(path string, cgroup *configs.Cgroup) error {
 
 func (s *HugetlbGroup) GetStats(path string, stats *cgroups.Stats) error {
 	hugetlbStats := cgroups.HugetlbStats{}
+	if !cgroups.PathExists(path) {
+		return nil
+	}
 	for _, pageSize := range HugePageSizes {
 		usage := strings.Join([]string{"hugetlb", pageSize, "usage_in_bytes"}, ".")
 		value, err := fscommon.GetCgroupParamUint(path, usage)
diff --git a/libcontainer/cgroups/fs/pids.go b/libcontainer/cgroups/fs/pids.go
index 1db0bc04..1d7b1c16 100644
--- a/libcontainer/cgroups/fs/pids.go
+++ b/libcontainer/cgroups/fs/pids.go
@@ -45,6 +45,9 @@ func (s *PidsGroup) Set(path string, cgroup *configs.Cgroup) error {
 }
 
 func (s *PidsGroup) GetStats(path string, stats *cgroups.Stats) error {
+	if !cgroups.PathExists(path) {
+		return nil
+	}
 	current, err := fscommon.GetCgroupParamUint(path, "pids.current")
 	if err != nil {
 		return fmt.Errorf("failed to parse pids.current - %s", err)