Solve errcheck warnings (part 1)

drivers/aufs/aufs.go

@@ -683,7 +683,9 @@ func (a *Driver) Cleanup() error {
 func (a *Driver) aufsMount(ro []string, rw, target string, options graphdriver.MountOpts) (err error) {
 	defer func() {
 		if err != nil {
-			Unmount(target)
+			if err1 := Unmount(target); err1 != nil {
+				logrus.Warnf("Unmount %q: %v", target, err1)
+			}
 		}
 	}()
 

drivers/overlay/check.go

@@ -263,7 +263,11 @@ func supportsIdmappedLowerLayers(home string) (bool, error) {
 	if err := idmap.CreateIDMappedMount(lowerDir, lowerMappedDir, int(pid)); err != nil {
 		return false, fmt.Errorf("create mapped mount: %w", err)
 	}
-	defer unix.Unmount(lowerMappedDir, unix.MNT_DETACH)
+	defer func() {
+		if err := unix.Unmount(lowerMappedDir, unix.MNT_DETACH); err != nil {
+			logrus.Warnf("Unmount %q: %v", lowerMappedDir, err)
+		}
+	}()
 
 	opts := fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", lowerMappedDir, upperDir, workDir)
 	flags := uintptr(0)

drivers/overlay/overlay.go

@@ -1555,7 +1555,11 @@ func (d *Driver) get(id string, disableShifting bool, options graphdriver.MountO
 	composefsMounts := []string{}
 	defer func() {
 		for _, m := range composefsMounts {
-			defer unix.Unmount(m, unix.MNT_DETACH)
+			defer func(m string) {
+				if err := unix.Unmount(m, unix.MNT_DETACH); err != nil {
+					logrus.Warnf("Unmount %q: %v", m, err)
+				}
+			}(m)
 		}
 	}()
 
@@ -1659,7 +1663,11 @@ func (d *Driver) get(id string, disableShifting bool, options graphdriver.MountO
 				skipIDMappingLayers[composefsMount] = composefsMount
 				// overlay takes a reference on the mount, so it is safe to unmount
 				// the mapped idmounts as soon as the final overlay file system is mounted.
-				defer unix.Unmount(composefsMount, unix.MNT_DETACH)
+				defer func() {
+					if err := unix.Unmount(composefsMount, unix.MNT_DETACH); err != nil {
+						logrus.Warnf("Unmount %q: %v", composefsMount, err)
+					}
+				}()
 			}
 			absLowers = append(absLowers, composefsMount)
 			continue
@@ -1766,7 +1774,11 @@ func (d *Driver) get(id string, disableShifting bool, options graphdriver.MountO
 
 				// overlay takes a reference on the mount, so it is safe to unmount
 				// the mapped idmounts as soon as the final overlay file system is mounted.
-				defer unix.Unmount(root, unix.MNT_DETACH)
+				defer func() {
+					if err := unix.Unmount(root, unix.MNT_DETACH); err != nil {
+						logrus.Warnf("Unmount %q: %v", root, err)
+					}
+				}()
 			}
 
 			// relative path to the layer through the id mapped mount

drivers/zfs/zfs.go

@@ -240,7 +240,9 @@ func (d *Driver) cloneFilesystem(name, parentName string) error {
 	}
 
 	if err != nil {
-		snapshot.Destroy(zfs.DestroyDeferDeletion)
+		if err1 := snapshot.Destroy(zfs.DestroyDeferDeletion); err1 != nil {
+			logrus.Warnf("Destroy zfs.DestroyDeferDeletion: %v", err1)
+		}
 		return err
 	}
 	return snapshot.Destroy(zfs.DestroyDeferDeletion)

pkg/archive/archive_linux_test.go

@@ -93,9 +93,11 @@ func checkFileMode(t *testing.T, path string, perm os.FileMode) {
 }
 
 func TestOverlayTarUntar(t *testing.T) {
-	oldmask, err := system.Umask(0)
+	oldMask, err := system.Umask(0)
 	require.NoError(t, err)
-	defer system.Umask(oldmask)
+	defer func() {
+		_, _ = system.Umask(oldMask) // Ignore err. This can only fail with ErrNotSupportedPlatform, in which case we would have failed above.
+	}()
 
 	src := t.TempDir()
 	setupOverlayTestDir(t, src)
@@ -131,9 +133,11 @@ func TestOverlayTarUntar(t *testing.T) {
 }
 
 func TestOverlayTarAUFSUntar(t *testing.T) {
-	oldmask, err := system.Umask(0)
+	oldMask, err := system.Umask(0)
 	require.NoError(t, err)
-	defer system.Umask(oldmask)
+	defer func() {
+		_, _ = system.Umask(oldMask) // Ignore err. This can only fail with ErrNotSupportedPlatform, in which case we would have failed above.
+	}()
 
 	src := t.TempDir()
 	setupOverlayTestDir(t, src)

pkg/chrootarchive/diff_unix.go

@@ -40,11 +40,13 @@ func applyLayer() {
 	}
 
 	// We need to be able to set any perms
-	oldmask, err := system.Umask(0)
-	defer system.Umask(oldmask)
+	oldMask, err := system.Umask(0)
 	if err != nil {
 		fatal(err)
 	}
+	defer func() {
+		_, _ = system.Umask(oldMask) // Ignore err. This can only fail with ErrNotSupportedPlatform, in which case we would have failed above.
+	}()
 
 	if err := json.Unmarshal([]byte(os.Getenv("OPT")), &options); err != nil {
 		fatal(err)