mount: fix check for empty mount point on Linux #3562

cmd/mountlib/check_linux.go

@@ -33,12 +33,20 @@ func CheckMountEmpty(mountpoint string) error {
 	if err != nil {
 		return fmt.Errorf("cannot read %s: %w", mtabPath, err)
 	}
+	foundAutofs := false
 	for _, entry := range entries {
-		if entry.Dir == mountpointAbs && entry.Type != "autofs" {
+		if entry.Dir == mountpointAbs {
+			if entry.Type != "autofs" {
 				return fmt.Errorf(msg, mountpointAbs)
 			}
+			foundAutofs = true
 		}
+	}
+	// It isn't safe to list an autofs in the middle of mounting
+	if foundAutofs {
 		return nil
+	}
+	return checkMountEmpty(mountpoint)
 }
 
 // CheckMountReady checks whether mountpoint is mounted by rclone.

cmd/mountlib/check_other.go

@@ -4,33 +4,13 @@
 package mountlib
 
 import (
-	"fmt"
-	"io"
-	"os"
 	"time"
-
-	"github.com/rclone/rclone/fs"
 )
 
 // CheckMountEmpty checks if mountpoint folder is empty.
 // On non-Linux unixes we list directory to ensure that.
 func CheckMountEmpty(mountpoint string) error {
-	fp, err := os.Open(mountpoint)
-	if err != nil {
-		return fmt.Errorf("cannot open: %s: %w", mountpoint, err)
-	}
-	defer fs.CheckClose(fp, &err)
-
-	_, err = fp.Readdirnames(1)
-	if err == io.EOF {
-		return nil
-	}
-
-	const msg = "directory is not empty, use --allow-non-empty to mount anyway: %s"
-	if err == nil {
-		return fmt.Errorf(msg, mountpoint)
-	}
-	return fmt.Errorf(msg+": %w", mountpoint, err)
+	return checkMountEmpty(mountpoint)
 }
 
 // CheckMountReady should check if mountpoint is mounted by rclone.

cmd/mountlib/utils.go

@@ -2,6 +2,8 @@ package mountlib
 
 import (
 	"fmt"
+	"io"
+	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -84,6 +86,26 @@ func (m *MountPoint) CheckAllowed() error {
 	return nil
 }
 
+// checkMountEmpty checks if mountpoint folder is empty by listing it.
+func checkMountEmpty(mountpoint string) error {
+	fp, err := os.Open(mountpoint)
+	if err != nil {
+		return fmt.Errorf("cannot open: %s: %w", mountpoint, err)
+	}
+	defer fs.CheckClose(fp, &err)
+
+	_, err = fp.Readdirnames(1)
+	if err == io.EOF {
+		return nil
+	}
+
+	const msg = "%q is not empty, use --allow-non-empty to mount anyway"
+	if err == nil {
+		return fmt.Errorf(msg, mountpoint)
+	}
+	return fmt.Errorf(msg+": %w", mountpoint, err)
+}
+
 // SetVolumeName with sensible default
 func (m *MountPoint) SetVolumeName(vol string) {
 	if vol == "" {