Merge pull request #2291 from kolyshkin/errors-unwrap-v2

Use errors.As() and errors.Is() to unwrap errors

libcontainer/cgroups/fs/apply_raw.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 	"sync"
+	"syscall"
 
 	"github.com/opencontainers/runc/libcontainer/cgroups"
 	"github.com/opencontainers/runc/libcontainer/configs"
@@ -110,14 +111,18 @@ func isIgnorableError(rootless bool, err error) bool {
 	if !rootless {
 		return false
 	}
+	// TODO: rm errors.Cause once we switch to %w everywhere
 	err = errors.Cause(err)
 	// Is it an ordinary EPERM?
-	if os.IsPermission(err) {
+	if errors.Is(err, os.ErrPermission) {
 		return true
 	}
 	// Handle some specific syscall errors.
-	errno := errors.Unwrap(err)
-	return errno == unix.EROFS || errno == unix.EPERM || errno == unix.EACCES
+	var errno syscall.Errno
+	if errors.As(err, &errno) {
+		return errno == unix.EROFS || errno == unix.EPERM || errno == unix.EACCES
+	}
+	return false
 }
 
 func (m *Manager) getSubsystems() subsystemSet {

libcontainer/cgroups/fs/kmem.go

@@ -47,7 +47,7 @@ func setKernelMemory(path string, kernelMemoryLimit int64) error {
 		// The EBUSY signal is returned on attempts to write to the
 		// memory.kmem.limit_in_bytes file if the cgroup has children or
 		// once tasks have been attached to the cgroup
-		if errors.Unwrap(err) == unix.EBUSY {
+		if errors.Is(err, unix.EBUSY) {
 			return fmt.Errorf("failed to set %s, because either tasks have already joined this cgroup or it has children", cgroupKernelMemoryLimit)
 		}
 		return fmt.Errorf("failed to write %v to %v: %v", kernelMemoryLimit, cgroupKernelMemoryLimit, err)

libcontainer/cgroups/fs2/pids.go

@@ -28,7 +28,7 @@ func statPidsWithoutController(dirPath string, stats *cgroups.Stats) error {
 	// if the controller is not enabled, let's read PIDS from cgroups.procs
 	// (or threads if cgroup.threads is enabled)
 	contents, err := ioutil.ReadFile(filepath.Join(dirPath, "cgroup.procs"))
-	if err != nil && errors.Unwrap(err) == unix.ENOTSUP {
+	if errors.Is(err, unix.ENOTSUP) {
 		contents, err = ioutil.ReadFile(filepath.Join(dirPath, "cgroup.threads"))
 	}
 	if err != nil {

libcontainer/cgroups/fscommon/fscommon.go

@@ -41,10 +41,20 @@ func ReadFile(dir, file string) (string, error) {
 func retryingWriteFile(filename string, data []byte, perm os.FileMode) error {
 	for {
 		err := ioutil.WriteFile(filename, data, perm)
-		if errors.Unwrap(err) == syscall.EINTR {
+		if isInterruptedWriteFile(err) {
 			logrus.Infof("interrupted while writing %s to %s", string(data), filename)
 			continue
 		}
 		return err
 	}
 }
+
+func isInterruptedWriteFile(err error) bool {
+	if patherr, ok := err.(*os.PathError); ok {
+		errno, ok2 := patherr.Err.(syscall.Errno)
+		if ok2 && errno == syscall.EINTR {
+			return true
+		}
+	}
+	return false
+}

libcontainer/cgroups/utils.go

@@ -576,7 +576,7 @@ func WriteCgroupProc(dir string, pid int) error {
 
 		// EINVAL might mean that the task being added to cgroup.procs is in state
 		// TASK_NEW. We should attempt to do so again.
-		if errors.Unwrap(err) == unix.EINVAL {
+		if errors.Is(err, unix.EINVAL) {
 			time.Sleep(30 * time.Millisecond)
 			continue
 		}

libcontainer/container_linux.go

@@ -1855,7 +1855,7 @@ func (c *linuxContainer) isPaused() (bool, error) {
 	data, err := ioutil.ReadFile(filepath.Join(fcg, filename))
 	if err != nil {
 		// If freezer cgroup is not mounted, the container would just be not paused.
-		if os.IsNotExist(err) || errors.Unwrap(err) == syscall.ENODEV {
+		if os.IsNotExist(err) || errors.Is(err, syscall.ENODEV) {
 			return false, nil
 		}
 		return false, newSystemErrorWithCause(err, "checking if container is paused")