utils: call GetRootlessRuntimeDir once

use a sync.Once to potentially avoid multiple system calls everytime
the function is called.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/util/utils.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
@@ -181,38 +182,54 @@ func ParseIDMapping(UIDMapSlice, GIDMapSlice []string, subUIDMap, subGIDMap stri
 	return &options, nil
 }
 
+var (
+	rootlessRuntimeDirOnce sync.Once
+	rootlessRuntimeDir     string
+)
+
 // GetRootlessRuntimeDir returns the runtime directory when running as non root
 func GetRootlessRuntimeDir() (string, error) {
-	runtimeDir := os.Getenv("XDG_RUNTIME_DIR")
+	var rootlessRuntimeDirError error
-	uid := fmt.Sprintf("%d", rootless.GetRootlessUID())
+
-	if runtimeDir == "" {
+	rootlessRuntimeDirOnce.Do(func() {
-		tmpDir := filepath.Join("/run", "user", uid)
+		runtimeDir := os.Getenv("XDG_RUNTIME_DIR")
-		os.MkdirAll(tmpDir, 0700)
+		uid := fmt.Sprintf("%d", rootless.GetRootlessUID())
-		st, err := os.Stat(tmpDir)
+		if runtimeDir == "" {
-		if err == nil && int(st.Sys().(*syscall.Stat_t).Uid) == os.Geteuid() && st.Mode().Perm() == 0700 {
+			tmpDir := filepath.Join("/run", "user", uid)
-			runtimeDir = tmpDir
+			os.MkdirAll(tmpDir, 0700)
+			st, err := os.Stat(tmpDir)
+			if err == nil && int(st.Sys().(*syscall.Stat_t).Uid) == os.Geteuid() && st.Mode().Perm() == 0700 {
+				runtimeDir = tmpDir
+			}
 		}
+		if runtimeDir == "" {
+			tmpDir := filepath.Join(os.TempDir(), fmt.Sprintf("run-%s", uid))
+			os.MkdirAll(tmpDir, 0700)
+			st, err := os.Stat(tmpDir)
+			if err == nil && int(st.Sys().(*syscall.Stat_t).Uid) == os.Geteuid() && st.Mode().Perm() == 0700 {
+				runtimeDir = tmpDir
+			}
+		}
+		if runtimeDir == "" {
+			home := os.Getenv("HOME")
+			if home == "" {
+				rootlessRuntimeDirError = fmt.Errorf("neither XDG_RUNTIME_DIR nor HOME was set non-empty")
+				return
+			}
+			resolvedHome, err := filepath.EvalSymlinks(home)
+			if err != nil {
+				rootlessRuntimeDirError = errors.Wrapf(err, "cannot resolve %s", home)
+				return
+			}
+			runtimeDir = filepath.Join(resolvedHome, "rundir")
+		}
+		rootlessRuntimeDir = runtimeDir
+	})
+
+	if rootlessRuntimeDirError != nil {
+		return "", rootlessRuntimeDirError
 	}
-	if runtimeDir == "" {
+	return rootlessRuntimeDir, nil
-		tmpDir := filepath.Join(os.TempDir(), fmt.Sprintf("run-%s", uid))
-		os.MkdirAll(tmpDir, 0700)
-		st, err := os.Stat(tmpDir)
-		if err == nil && int(st.Sys().(*syscall.Stat_t).Uid) == os.Geteuid() && st.Mode().Perm() == 0700 {
-			runtimeDir = tmpDir
-		}
-	}
-	if runtimeDir == "" {
-		home := os.Getenv("HOME")
-		if home == "" {
-			return "", fmt.Errorf("neither XDG_RUNTIME_DIR nor HOME was set non-empty")
-		}
-		resolvedHome, err := filepath.EvalSymlinks(home)
-		if err != nil {
-			return "", errors.Wrapf(err, "cannot resolve %s", home)
-		}
-		runtimeDir = filepath.Join(resolvedHome, "rundir")
-	}
-	return runtimeDir, nil
 }
 
 // GetRootlessDirInfo returns the parent path of where the storage for containers and