Merge pull request #2280 from kolyshkin/errors-unwrap

Use errors.Unwrap() where possible

libcontainer/cgroups/fs/apply_raw.go

@@ -110,21 +110,13 @@ func isIgnorableError(rootless bool, err error) bool {
 	if !rootless {
 		return false
 	}
+	err = errors.Cause(err)
 	// Is it an ordinary EPERM?
-	if os.IsPermission(errors.Cause(err)) {
+	if os.IsPermission(err) {
 		return true
 	}
-
-	// Try to handle other errnos.
-	var errno error
-	switch err := errors.Cause(err).(type) {
-	case *os.PathError:
-		errno = err.Err
-	case *os.LinkError:
-		errno = err.Err
-	case *os.SyscallError:
-		errno = err.Err
-	}
+	// Handle some specific syscall errors.
+	errno := errors.Unwrap(err)
 	return errno == unix.EROFS || errno == unix.EPERM || errno == unix.EACCES
 }
 

libcontainer/cgroups/fs/kmem.go

@@ -6,10 +6,8 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"strconv"
-	"syscall" // for Errno type only
 
 	"github.com/opencontainers/runc/libcontainer/cgroups"
 	"golang.org/x/sys/unix"
@@ -49,12 +47,8 @@ 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 pathErr, ok := err.(*os.PathError); ok {
-			if errNo, ok := pathErr.Err.(syscall.Errno); ok {
-				if errNo == unix.EBUSY {
-					return fmt.Errorf("failed to set %s, because either tasks have already joined this cgroup or it has children", cgroupKernelMemoryLimit)
-				}
-			}
+		if errors.Unwrap(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

@@ -4,7 +4,6 @@ package fs2
 
 import (
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"strings"
 
@@ -25,20 +24,11 @@ func setPids(dirPath string, cgroup *configs.Cgroup) error {
 	return nil
 }
 
-func isNOTSUP(err error) bool {
-	switch err := err.(type) {
-	case *os.PathError:
-		return err.Err == unix.ENOTSUP
-	default:
-		return false
-	}
-}
-
 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 && isNOTSUP(err) {
+	if err != nil && errors.Unwrap(err) == unix.ENOTSUP {
 		contents, err = ioutil.ReadFile(filepath.Join(dirPath, "cgroup.threads"))
 	}
 	if err != nil {

libcontainer/cgroups/fscommon/fscommon.go

@@ -41,20 +41,10 @@ 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 isInterruptedWriteFile(err) {
+		if errors.Unwrap(err) == syscall.EINTR {
 			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 isEINVAL(err) {
+		if errors.Unwrap(err) == unix.EINVAL {
 			time.Sleep(30 * time.Millisecond)
 			continue
 		}
@@ -586,15 +586,6 @@ func WriteCgroupProc(dir string, pid int) error {
 	return err
 }
 
-func isEINVAL(err error) bool {
-	switch err := err.(type) {
-	case *os.PathError:
-		return err.Err == unix.EINVAL
-	default:
-		return false
-	}
-}
-
 // Since the OCI spec is designed for cgroup v1, in some cases
 // there is need to convert from the cgroup v1 configuration to cgroup v2
 // the formula for BlkIOWeight is y = (1 + (x - 10) * 9999 / 990)

libcontainer/container_linux.go

@@ -1855,10 +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) {
-			return false, nil
-		}
-		if pathError, isPathError := err.(*os.PathError); isPathError && pathError.Err == syscall.ENODEV {
+		if os.IsNotExist(err) || errors.Unwrap(err) == syscall.ENODEV {
 			return false, nil
 		}
 		return false, newSystemErrorWithCause(err, "checking if container is paused")