Extract mount into pkg.

Mount is self contained and generic, it should be in pkg, to allow other pkg modules to use it.

Docker-DCO-1.1-Signed-off-by: Paul Nasrat <pnasrat@gmail.com> (github: pnasrat)

mount/mountinfo.go

@@ -0,0 +1,79 @@
+package mount
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+const (
+	/* 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
+	   (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
+
+	   (1) mount ID:  unique identifier of the mount (may be reused after umount)
+	   (2) parent ID:  ID of parent (or of self for the top of the mount tree)
+	   (3) major:minor:  value of st_dev for files on filesystem
+	   (4) root:  root of the mount within the filesystem
+	   (5) mount point:  mount point relative to the process's root
+	   (6) mount options:  per mount options
+	   (7) optional fields:  zero or more fields of the form "tag[:value]"
+	   (8) separator:  marks the end of the optional fields
+	   (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 "
+)
+
+type MountInfo struct {
+	Id, Parent, Major, Minor int
+	Root, Mountpoint, Opts   string
+	Fstype, Source, VfsOpts  string
+}
+
+// Parse /proc/self/mountinfo because comparing Dev and ino does not work from bind mounts
+func parseMountTable() ([]*MountInfo, error) {
+	f, err := os.Open("/proc/self/mountinfo")
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	return parseInfoFile(f)
+}
+
+func parseInfoFile(r io.Reader) ([]*MountInfo, error) {
+	var (
+		s   = bufio.NewScanner(r)
+		out = []*MountInfo{}
+	)
+
+	for s.Scan() {
+		if err := s.Err(); err != nil {
+			return nil, err
+		}
+
+		var (
+			p    = &MountInfo{}
+			text = s.Text()
+		)
+
+		if _, err := fmt.Sscanf(text, mountinfoFormat,
+			&p.Id, &p.Parent, &p.Major, &p.Minor,
+			&p.Root, &p.Mountpoint, &p.Opts); err != nil {
+			return nil, fmt.Errorf("Scanning '%s' failed: %s", text, err)
+		}
+		// Safe as mountinfo encodes mountpoints with spaces as \040.
+		index := strings.Index(text, " - ")
+		postSeparatorFields := strings.Fields(text[index+3:])
+		if len(postSeparatorFields) != 3 {
+			return nil, fmt.Errorf("Error did not find 3 fields post '-' in '%s'", text)
+		}
+		p.Fstype = postSeparatorFields[0]
+		p.Source = postSeparatorFields[1]
+		p.VfsOpts = postSeparatorFields[2]
+		out = append(out, p)
+	}
+	return out, nil
+}