btrfs: auto-detect device

mountinfo/mountinfo.go

@@ -0,0 +1,40 @@
+package mountinfo
+
+// Info reveals information about a particular mounted filesystem. This
+// struct is populated from the content in the /proc/<pid>/mountinfo file.
+type Info struct {
+	// ID is a unique identifier of the mount (may be reused after umount).
+	ID int
+
+	// Parent indicates the ID of the mount parent (or of self for the top of the
+	// mount tree).
+	Parent int
+
+	// Major indicates one half of the device ID which identifies the device class.
+	Major int
+
+	// Minor indicates one half of the device ID which identifies a specific
+	// instance of device.
+	Minor int
+
+	// Root of the mount within the filesystem.
+	Root string
+
+	// Mountpoint indicates the mount point relative to the process's root.
+	Mountpoint string
+
+	// Options represents mount-specific options.
+	Options string
+
+	// Optional represents optional fields.
+	Optional string
+
+	// FSType indicates the type of filesystem, such as EXT3.
+	FSType string
+
+	// Source indicates filesystem specific information or "none".
+	Source string
+
+	// VFSOptions represents per super block options.
+	VFSOptions string
+}

mountinfo/mountinfo_freebsd.go

@@ -0,0 +1,45 @@
+package mountinfo
+
+/*
+#include <sys/param.h>
+#include <sys/ucred.h>
+#include <sys/mount.h>
+*/
+import "C"
+
+import (
+	"fmt"
+	"reflect"
+	"unsafe"
+)
+
+// Self retrieves a list of mounts for the current running process.
+func Self() ([]Info, error) {
+	var rawEntries *C.struct_statfs
+
+	count := int(C.getmntinfo(&rawEntries, C.MNT_WAIT))
+	if count == 0 {
+		return nil, fmt.Errorf("Failed to call getmntinfo")
+	}
+
+	var entries []C.struct_statfs
+	header := (*reflect.SliceHeader)(unsafe.Pointer(&entries))
+	header.Cap = count
+	header.Len = count
+	header.Data = uintptr(unsafe.Pointer(rawEntries))
+
+	var out []Info
+	for _, entry := range entries {
+		var mountinfo Info
+		mountinfo.Mountpoint = C.GoString(&entry.f_mntonname[0])
+		mountinfo.Source = C.GoString(&entry.f_mntfromname[0])
+		mountinfo.FSType = C.GoString(&entry.f_fstypename[0])
+		out = append(out, mountinfo)
+	}
+	return out, nil
+}
+
+// PID collects the mounts for a specific process ID.
+func PID(pid int) ([]Info, error) {
+	return nil, fmt.Errorf("mountinfo.PID is not implemented on freebsd")
+}

mountinfo/mountinfo_linux.go

@@ -0,0 +1,94 @@
+// +build linux
+
+package mountinfo
+
+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 %s"
+)
+
+// Self retrieves a list of mounts for the current running process.
+func Self() ([]Info, 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) ([]Info, error) {
+	var (
+		s   = bufio.NewScanner(r)
+		out = []Info{}
+	)
+
+	for s.Scan() {
+		if err := s.Err(); err != nil {
+			return nil, err
+		}
+
+		var (
+			p              = Info{}
+			text           = s.Text()
+			optionalFields string
+		)
+
+		if _, err := fmt.Sscanf(text, mountinfoFormat,
+			&p.ID, &p.Parent, &p.Major, &p.Minor,
+			&p.Root, &p.Mountpoint, &p.Options, &optionalFields); 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 found less than 3 fields post '-' in %q", text)
+		}
+
+		if optionalFields != "-" {
+			p.Optional = optionalFields
+		}
+
+		p.FSType = postSeparatorFields[0]
+		p.Source = postSeparatorFields[1]
+		p.VFSOptions = strings.Join(postSeparatorFields[2:], " ")
+		out = append(out, p)
+	}
+	return out, nil
+}
+
+// PID collects the mounts for a specific process ID. If the process
+// ID is unknown, it is better to use `Self` which will inspect
+// "/proc/self/mountinfo" instead.
+func PID(pid int) ([]Info, error) {
+	f, err := os.Open(fmt.Sprintf("/proc/%d/mountinfo", pid))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	return parseInfoFile(f)
+}