github.com/ssdev-go/moby@v17.12.1-ce-rc2+incompatible/pkg/mount/mountinfo_linux.go (about)

     1  // +build linux
     2  
     3  package mount
     4  
     5  import (
     6  	"bufio"
     7  	"fmt"
     8  	"io"
     9  	"os"
    10  	"strings"
    11  )
    12  
    13  const (
    14  	/* 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
    15  	   (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
    16  
    17  	   (1) mount ID:  unique identifier of the mount (may be reused after umount)
    18  	   (2) parent ID:  ID of parent (or of self for the top of the mount tree)
    19  	   (3) major:minor:  value of st_dev for files on filesystem
    20  	   (4) root:  root of the mount within the filesystem
    21  	   (5) mount point:  mount point relative to the process's root
    22  	   (6) mount options:  per mount options
    23  	   (7) optional fields:  zero or more fields of the form "tag[:value]"
    24  	   (8) separator:  marks the end of the optional fields
    25  	   (9) filesystem type:  name of filesystem of the form "type[.subtype]"
    26  	   (10) mount source:  filesystem specific information or "none"
    27  	   (11) super options:  per super block options*/
    28  	mountinfoFormat = "%d %d %d:%d %s %s %s %s"
    29  )
    30  
    31  // Parse /proc/self/mountinfo because comparing Dev and ino does not work from
    32  // bind mounts
    33  func parseMountTable() ([]*Info, error) {
    34  	f, err := os.Open("/proc/self/mountinfo")
    35  	if err != nil {
    36  		return nil, err
    37  	}
    38  	defer f.Close()
    39  
    40  	return parseInfoFile(f)
    41  }
    42  
    43  func parseInfoFile(r io.Reader) ([]*Info, error) {
    44  	var (
    45  		s   = bufio.NewScanner(r)
    46  		out = []*Info{}
    47  	)
    48  
    49  	for s.Scan() {
    50  		if err := s.Err(); err != nil {
    51  			return nil, err
    52  		}
    53  
    54  		var (
    55  			p              = &Info{}
    56  			text           = s.Text()
    57  			optionalFields string
    58  		)
    59  
    60  		if _, err := fmt.Sscanf(text, mountinfoFormat,
    61  			&p.ID, &p.Parent, &p.Major, &p.Minor,
    62  			&p.Root, &p.Mountpoint, &p.Opts, &optionalFields); err != nil {
    63  			return nil, fmt.Errorf("Scanning '%s' failed: %s", text, err)
    64  		}
    65  		// Safe as mountinfo encodes mountpoints with spaces as \040.
    66  		index := strings.Index(text, " - ")
    67  		postSeparatorFields := strings.Fields(text[index+3:])
    68  		if len(postSeparatorFields) < 3 {
    69  			return nil, fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
    70  		}
    71  
    72  		if optionalFields != "-" {
    73  			p.Optional = optionalFields
    74  		}
    75  
    76  		p.Fstype = postSeparatorFields[0]
    77  		p.Source = postSeparatorFields[1]
    78  		p.VfsOpts = strings.Join(postSeparatorFields[2:], " ")
    79  		out = append(out, p)
    80  	}
    81  	return out, nil
    82  }
    83  
    84  // PidMountInfo collects the mounts for a specific process ID. If the process
    85  // ID is unknown, it is better to use `GetMounts` which will inspect
    86  // "/proc/self/mountinfo" instead.
    87  func PidMountInfo(pid int) ([]*Info, error) {
    88  	f, err := os.Open(fmt.Sprintf("/proc/%d/mountinfo", pid))
    89  	if err != nil {
    90  		return nil, err
    91  	}
    92  	defer f.Close()
    93  
    94  	return parseInfoFile(f)
    95  }