pkg/mount: include optional field

one linux, the optional field designates the sharedsubtree information,
if any.

Signed-off-by: Vincent Batts <vbatts@redhat.com>

pkg/mount/mountinfo.go

@@ -1,7 +1,7 @@
 package mount
 
 type MountInfo struct {
-	Id, Parent, Major, Minor int
-	Root, Mountpoint, Opts   string
-	Fstype, Source, VfsOpts  string
+	Id, Parent, Major, Minor         int
+	Root, Mountpoint, Opts, Optional string
+	Fstype, Source, VfsOpts          string
 }

pkg/mount/mountinfo_linux.go

@@ -23,7 +23,7 @@ const (
 	   (9) filesystem type:  name of filesystem of the form "type[.subtype]"
 	   (10) mount source:  filesystem specific information or "none"
 	   (11) super options:  per super block options*/
-	mountinfoFormat = "%d %d %d:%d %s %s %s "
+	mountinfoFormat = "%d %d %d:%d %s %s %s %s"
 )
 
 // Parse /proc/self/mountinfo because comparing Dev and ino does not work from bind mounts
@@ -49,13 +49,14 @@ func parseInfoFile(r io.Reader) ([]*MountInfo, error) {
 		}
 
 		var (
-			p    = &MountInfo{}
-			text = s.Text()
+			p              = &MountInfo{}
+			text           = s.Text()
+			optionalFields string
 		)
 
 		if _, err := fmt.Sscanf(text, mountinfoFormat,
 			&p.Id, &p.Parent, &p.Major, &p.Minor,
-			&p.Root, &p.Mountpoint, &p.Opts); err != nil {
+			&p.Root, &p.Mountpoint, &p.Opts, &optionalFields); err != nil {
 			return nil, fmt.Errorf("Scanning '%s' failed: %s", text, err)
 		}
 		// Safe as mountinfo encodes mountpoints with spaces as \040.
@@ -65,6 +66,10 @@ func parseInfoFile(r io.Reader) ([]*MountInfo, error) {
 			return nil, fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
 		}
 
+		if optionalFields != "-" {
+			p.Optional = optionalFields
+		}
+
 		p.Fstype = postSeparatorFields[0]
 		p.Source = postSeparatorFields[1]
 		p.VfsOpts = strings.Join(postSeparatorFields[2:], " ")