aboutsummaryrefslogtreecommitdiff
path: root/filesystem/mountpoint.go
diff options
context:
space:
mode:
Diffstat (limited to 'filesystem/mountpoint.go')
-rw-r--r--filesystem/mountpoint.go596
1 files changed, 454 insertions, 142 deletions
diff --git a/filesystem/mountpoint.go b/filesystem/mountpoint.go
index 12016dd..9be54a4 100644
--- a/filesystem/mountpoint.go
+++ b/filesystem/mountpoint.go
@@ -22,24 +22,14 @@
package filesystem
import (
- "io/ioutil"
- "os"
-)
-
-/*
-#include <mntent.h> // setmntent, getmntent, endmntent
-
-// The file containing mountpoints info and how we should read it
-const char* mountpoints_filename = "/proc/mounts";
-const char* read_mode = "r";
-*/
-import "C"
-
-import (
+ "bufio"
"fmt"
+ "io"
"log"
+ "os"
"path/filepath"
"sort"
+ "strconv"
"strings"
"sync"
@@ -47,86 +37,326 @@ import (
)
var (
- // These maps hold data about the state of the system's mountpoints.
+ // These maps hold data about the state of the system's filesystems.
+ //
+ // They only contain one Mount per filesystem, even if there are
+ // additional bind mounts, since we want to store fscrypt metadata in
+ // only one place per filesystem. When it is ambiguous which Mount
+ // should be used for a filesystem, mountsByDevice will contain an
+ // explicit nil entry, and mountsByPath won't contain an entry.
+ mountsByDevice map[DeviceNumber]*Mount
mountsByPath map[string]*Mount
- mountsByDevice map[string][]*Mount
// Used to make the mount functions thread safe
mountMutex sync.Mutex
// True if the maps have been successfully initialized.
mountsInitialized bool
// Supported tokens for filesystem links
uuidToken = "UUID"
+ pathToken = "PATH"
// Location to perform UUID lookup
uuidDirectory = "/dev/disk/by-uuid"
)
-// getMountInfo populates the Mount mappings by parsing the filesystem
-// description file using the getmntent functions. Returns ErrBadLoad if the
-// Mount mappings cannot be populated.
-func getMountInfo() error {
- if mountsInitialized {
- return nil
+// Unescape octal-encoded escape sequences in a string from the mountinfo file.
+// The kernel encodes the ' ', '\t', '\n', and '\\' bytes this way. This
+// function exactly inverts what the kernel does, including by preserving
+// invalid UTF-8.
+func unescapeString(str string) string {
+ var sb strings.Builder
+ for i := 0; i < len(str); i++ {
+ b := str[i]
+ if b == '\\' && i+3 < len(str) {
+ if parsed, err := strconv.ParseInt(str[i+1:i+4], 8, 8); err == nil {
+ b = uint8(parsed)
+ i += 3
+ }
+ }
+ sb.WriteByte(b)
}
+ return sb.String()
+}
- // make new maps
- mountsByPath = make(map[string]*Mount)
- mountsByDevice = make(map[string][]*Mount)
+// EscapeString is the reverse of unescapeString. Use this to avoid injecting
+// spaces or newlines into output that uses these characters as separators.
+func EscapeString(str string) string {
+ var sb strings.Builder
+ for _, b := range []byte(str) {
+ switch b {
+ case ' ', '\t', '\n', '\\':
+ sb.WriteString(fmt.Sprintf("\\%03o", b))
+ default:
+ sb.WriteByte(b)
+ }
+ }
+ return sb.String()
+}
- // Load the mount information from mountpoints_filename
- fileHandle := C.setmntent(C.mountpoints_filename, C.read_mode)
- if fileHandle == nil {
- return errors.Wrapf(ErrGlobalMountInfo, "could not read %q",
- C.GoString(C.mountpoints_filename))
+func getDeviceName(num DeviceNumber, mountSource string) string {
+ // When possible, get the device name via the device number rather than
+ // use the mount source field directly. This is necessary to handle a
+ // rootfs that was mounted via the kernel command line, since mountinfo
+ // always shows /dev/root for that.
+ linkPath := fmt.Sprintf("/sys/dev/block/%v", num)
+ if target, err := os.Readlink(linkPath); err == nil {
+ derivedDeviceName := fmt.Sprintf("/dev/%s", filepath.Base(target))
+ if _, err := os.Stat(derivedDeviceName); err == nil {
+ return derivedDeviceName
+ }
+ }
+ // Sysfs is not mounted or is incomplete, or the device nodes are not in
+ // the standard location. Fall back to using the mount source field if
+ // it looks like a path.
+ if strings.HasPrefix(mountSource, "/") {
+ return mountSource
}
- defer C.endmntent(fileHandle)
+ return ""
+}
- for {
- entry := C.getmntent(fileHandle)
- // When getmntent returns nil, we have read all of the entries.
- if entry == nil {
- mountsInitialized = true
+// Parse one line of /proc/self/mountinfo.
+//
+// The line contains the following space-separated fields:
+//
+// [0] mount ID
+// [1] parent ID
+// [2] major:minor
+// [3] root
+// [4] mount point
+// [5] mount options
+// [6...n-1] optional field(s)
+// [n] separator
+// [n+1] filesystem type
+// [n+2] mount source
+// [n+3] super options
+//
+// For more details, see https://www.kernel.org/doc/Documentation/filesystems/proc.txt
+func parseMountInfoLine(line string) *Mount {
+ fields := strings.Split(line, " ")
+ if len(fields) < 10 {
+ return nil
+ }
+
+ // Count the optional fields. In case new fields are appended later,
+ // don't simply assume that n == len(fields) - 4.
+ n := 6
+ for fields[n] != "-" {
+ n++
+ if n >= len(fields) {
return nil
}
+ }
+ if n+3 >= len(fields) {
+ return nil
+ }
+
+ var mnt *Mount = &Mount{}
+ var err error
+ mnt.DeviceNumber, err = newDeviceNumberFromString(fields[2])
+ if err != nil {
+ return nil
+ }
+ mnt.Subtree = unescapeString(fields[3])
+ mnt.Path = unescapeString(fields[4])
+ for _, opt := range strings.Split(fields[5], ",") {
+ if opt == "ro" {
+ mnt.ReadOnly = true
+ }
+ }
+ mnt.FilesystemType = unescapeString(fields[n+1])
+ mnt.Device = getDeviceName(mnt.DeviceNumber, unescapeString(fields[n+2]))
+ return mnt
+}
+
+type mountpointTreeNode struct {
+ mount *Mount
+ parent *mountpointTreeNode
+ children []*mountpointTreeNode
+}
- // Create the Mount structure by converting types.
- mnt := Mount{
- Path: C.GoString(entry.mnt_dir),
- Filesystem: C.GoString(entry.mnt_type),
- Options: strings.Split(C.GoString(entry.mnt_opts), ","),
+func addUncontainedSubtreesRecursive(dst map[string]bool,
+ node *mountpointTreeNode, allUncontainedSubtrees map[string]bool) {
+ if allUncontainedSubtrees[node.mount.Subtree] {
+ dst[node.mount.Subtree] = true
+ }
+ for _, child := range node.children {
+ addUncontainedSubtreesRecursive(dst, child, allUncontainedSubtrees)
+ }
+}
+
+// findMainMount finds the "main" Mount of a filesystem. The "main" Mount is
+// where the filesystem's fscrypt metadata is stored.
+//
+// Normally, there is just one Mount and it's of the entire filesystem
+// (mnt.Subtree == "/"). But in general, the filesystem might be mounted in
+// multiple places, including "bind mounts" where mnt.Subtree != "/". Also, the
+// filesystem might have a combination of read-write and read-only mounts.
+//
+// To handle most cases, we could just choose a mount with mnt.Subtree == "/",
+// preferably a read-write mount. However, that doesn't work in containers
+// where the "/" subtree might not be mounted. Here's a real-world example:
+//
+// mnt.Subtree mnt.Path
+// ----------- --------
+// /var/lib/lxc/base/rootfs /
+// /var/cache/pacman/pkg /var/cache/pacman/pkg
+// /srv/repo/x86_64 /srv/http/x86_64
+//
+// In this case, all mnt.Subtree are independent. To handle this case, we must
+// choose the Mount whose mnt.Path contains the others, i.e. the first one.
+// Note: the fscrypt metadata won't be usable from outside the container since
+// it won't be at the real root of the filesystem, but that may be acceptable.
+//
+// However, we can't look *only* at mnt.Path, since in some cases mnt.Subtree is
+// needed to correctly handle bind mounts. For example, in the following case,
+// the first Mount should be chosen:
+//
+// mnt.Subtree mnt.Path
+// ----------- --------
+// /foo /foo
+// /foo/dir /dir
+//
+// To solve this, we divide the mounts into non-overlapping trees of mnt.Path.
+// Then, we choose one of these trees which contains (exactly or via path
+// prefix) *all* mnt.Subtree. We then return the root of this tree. In both
+// the above examples, this algorithm returns the first Mount.
+func findMainMount(filesystemMounts []*Mount) *Mount {
+ // Index this filesystem's mounts by path. Note: paths are unique here,
+ // since non-last mounts were already excluded earlier.
+ //
+ // Also build the set of all mounted subtrees.
+ filesystemMountsByPath := make(map[string]*mountpointTreeNode)
+ allSubtrees := make(map[string]bool)
+ for _, mnt := range filesystemMounts {
+ filesystemMountsByPath[mnt.Path] = &mountpointTreeNode{mount: mnt}
+ allSubtrees[mnt.Subtree] = true
+ }
+
+ // Divide the mounts into non-overlapping trees of mountpoints.
+ for path, mntNode := range filesystemMountsByPath {
+ for path != "/" && mntNode.parent == nil {
+ path = filepath.Dir(path)
+ if parent := filesystemMountsByPath[path]; parent != nil {
+ mntNode.parent = parent
+ parent.children = append(parent.children, mntNode)
+ }
}
+ }
- // Skip invalid mountpoints
- var err error
- if mnt.Path, err = cannonicalizePath(mnt.Path); err != nil {
- log.Printf("getting mnt_dir: %v", err)
+ // Build the set of mounted subtrees that aren't contained in any other
+ // mounted subtree.
+ allUncontainedSubtrees := make(map[string]bool)
+ for subtree := range allSubtrees {
+ contained := false
+ for t := subtree; t != "/" && !contained; {
+ t = filepath.Dir(t)
+ contained = allSubtrees[t]
+ }
+ if !contained {
+ allUncontainedSubtrees[subtree] = true
+ }
+ }
+
+ // Select the root of a mountpoint tree whose mounted subtrees contain
+ // *all* mounted subtrees. Equivalently, select a mountpoint tree in
+ // which every uncontained subtree is mounted.
+ var mainMount *Mount
+ for _, mntNode := range filesystemMountsByPath {
+ mnt := mntNode.mount
+ if mntNode.parent != nil {
+ continue
+ }
+ uncontainedSubtrees := make(map[string]bool)
+ addUncontainedSubtreesRecursive(uncontainedSubtrees, mntNode, allUncontainedSubtrees)
+ if len(uncontainedSubtrees) != len(allUncontainedSubtrees) {
+ continue
+ }
+ // If there's more than one eligible mount, they should have the
+ // same Subtree. Otherwise it's ambiguous which one to use.
+ if mainMount != nil && mainMount.Subtree != mnt.Subtree {
+ log.Printf("Unsupported case: %q (%v) has multiple non-overlapping mounts. This filesystem will be ignored!",
+ mnt.Device, mnt.DeviceNumber)
+ return nil
+ }
+ // Prefer a read-write mount to a read-only one.
+ if mainMount == nil || mainMount.ReadOnly {
+ mainMount = mnt
+ }
+ }
+ return mainMount
+}
+
+// This is separate from loadMountInfo() only for unit testing.
+func readMountInfo(r io.Reader) error {
+ mountsByDevice = make(map[DeviceNumber]*Mount)
+ mountsByPath = make(map[string]*Mount)
+ allMountsByDevice := make(map[DeviceNumber][]*Mount)
+ allMountsByPath := make(map[string]*Mount)
+
+ scanner := bufio.NewScanner(r)
+ for scanner.Scan() {
+ line := scanner.Text()
+ mnt := parseMountInfoLine(line)
+ if mnt == nil {
+ log.Printf("ignoring invalid mountinfo line %q", line)
continue
}
+
// We can only use mountpoints that are directories for fscrypt.
if !isDir(mnt.Path) {
- log.Printf("mnt_dir %v: not a directory", mnt.Path)
+ log.Printf("ignoring mountpoint %q because it is not a directory", mnt.Path)
continue
}
// Note this overrides the info if we have seen the mountpoint
// earlier in the file. This is correct behavior because the
- // filesystems are listed in mount order.
- mountsByPath[mnt.Path] = &mnt
-
- deviceName, err := cannonicalizePath(C.GoString(entry.mnt_fsname))
- // Only use real valid devices (unlike cgroups, tmpfs, ...)
- if err == nil && isDevice(deviceName) {
- mnt.Device = deviceName
- mountsByDevice[deviceName] = append(mountsByDevice[deviceName], &mnt)
+ // mountpoints are listed in mount order.
+ allMountsByPath[mnt.Path] = mnt
+ }
+ // For each filesystem, choose a "main" Mount and discard any additional
+ // bind mounts. fscrypt only cares about the main Mount, since it's
+ // where the fscrypt metadata is stored. Store all the main Mounts in
+ // mountsByDevice and mountsByPath so that they can be found later.
+ for _, mnt := range allMountsByPath {
+ allMountsByDevice[mnt.DeviceNumber] =
+ append(allMountsByDevice[mnt.DeviceNumber], mnt)
+ }
+ for deviceNumber, filesystemMounts := range allMountsByDevice {
+ mnt := findMainMount(filesystemMounts)
+ mountsByDevice[deviceNumber] = mnt // may store an explicit nil entry
+ if mnt != nil {
+ mountsByPath[mnt.Path] = mnt
+ }
+ }
+ return nil
+}
+
+// loadMountInfo populates the Mount mappings by parsing /proc/self/mountinfo.
+// It returns an error if the Mount mappings cannot be populated.
+func loadMountInfo() error {
+ if !mountsInitialized {
+ file, err := os.Open("/proc/self/mountinfo")
+ if err != nil {
+ return err
}
+ defer file.Close()
+ if err := readMountInfo(file); err != nil {
+ return err
+ }
+ mountsInitialized = true
}
+ return nil
}
-// AllFilesystems lists all the Mounts on the current system ordered by path.
-// Use CheckSetup() to see if they are used with fscrypt.
+func filesystemLacksMainMountError(deviceNumber DeviceNumber) error {
+ return errors.Errorf("Device %q (%v) lacks a \"main\" mountpoint in the current mount namespace, so it's ambiguous where to store the fscrypt metadata.",
+ getDeviceName(deviceNumber, ""), deviceNumber)
+}
+
+// AllFilesystems lists all mounted filesystems ordered by path to their "main"
+// Mount. Use CheckSetup() to see if they are set up for use with fscrypt.
func AllFilesystems() ([]*Mount, error) {
mountMutex.Lock()
defer mountMutex.Unlock()
- if err := getMountInfo(); err != nil {
+ if err := loadMountInfo(); err != nil {
return nil, err
}
@@ -145,135 +375,217 @@ func UpdateMountInfo() error {
mountMutex.Lock()
defer mountMutex.Unlock()
mountsInitialized = false
- return getMountInfo()
+ return loadMountInfo()
}
-// FindMount returns the corresponding Mount object for some path in a
-// filesystem. Note that in the case of a bind mounts there may be two Mount
-// objects for the same underlying filesystem. An error is returned if the path
-// is invalid or we cannot load the required mount data. If a filesystem has
-// been updated since the last call to one of the mount functions, run
-// UpdateMountInfo to see changes.
+// FindMount returns the main Mount object for the filesystem which contains the
+// file at the specified path. An error is returned if the path is invalid or if
+// we cannot load the required mount data. If a mount has been updated since the
+// last call to one of the mount functions, run UpdateMountInfo to see changes.
func FindMount(path string) (*Mount, error) {
- path, err := cannonicalizePath(path)
+ mountMutex.Lock()
+ defer mountMutex.Unlock()
+ if err := loadMountInfo(); err != nil {
+ return nil, err
+ }
+ // First try to find the mount by the number of the containing device.
+ deviceNumber, err := getNumberOfContainingDevice(path)
if err != nil {
return nil, err
}
-
- mountMutex.Lock()
- defer mountMutex.Unlock()
- if err = getMountInfo(); err != nil {
+ mnt, ok := mountsByDevice[deviceNumber]
+ if ok {
+ if mnt == nil {
+ return nil, filesystemLacksMainMountError(deviceNumber)
+ }
+ return mnt, nil
+ }
+ // The mount couldn't be found by the number of the containing device.
+ // Fall back to walking up the directory hierarchy and checking for a
+ // mount at each directory path. This is necessary for btrfs, where
+ // files report a different st_dev from the /proc/self/mountinfo entry.
+ curPath, err := canonicalizePath(path)
+ if err != nil {
return nil, err
}
-
- // Traverse up the directory tree until we find a mountpoint
for {
- if mnt, ok := mountsByPath[path]; ok {
+ mnt := mountsByPath[curPath]
+ if mnt != nil {
return mnt, nil
}
-
// Move to the parent directory unless we have reached the root.
- parent := filepath.Dir(path)
- if parent == path {
- return nil, errors.Wrap(ErrNotAMountpoint, path)
+ parent := filepath.Dir(curPath)
+ if parent == curPath {
+ return nil, errors.Errorf("couldn't find mountpoint containing %q", path)
}
- path = parent
+ curPath = parent
}
}
-// GetMount returns the Mount object with a matching mountpoint. An error is
-// returned if the path is invalid or we cannot load the required mount data. If
-// a filesystem has been updated since the last call to one of the mount
-// functions, run UpdateMountInfo to see changes.
+// GetMount is like FindMount, except GetMount also returns an error if the path
+// doesn't name the same file as the filesystem's "main" Mount. For example, if
+// a filesystem is fully mounted at "/mnt" and if "/mnt/a" exists, then
+// FindMount("/mnt/a") will succeed whereas GetMount("/mnt/a") will fail. This
+// is true even if "/mnt/a" is a bind mount of part of the same filesystem.
func GetMount(mountpoint string) (*Mount, error) {
- mountpoint, err := cannonicalizePath(mountpoint)
+ mnt, err := FindMount(mountpoint)
+ if err != nil {
+ return nil, &ErrNotAMountpoint{mountpoint}
+ }
+ // Check whether 'mountpoint' names the same directory as 'mnt.Path'.
+ // Use os.SameFile() (i.e., compare inode numbers) rather than compare
+ // canonical paths, since filesystems may be mounted in multiple places.
+ fi1, err := os.Stat(mountpoint)
if err != nil {
return nil, err
}
-
- mountMutex.Lock()
- defer mountMutex.Unlock()
- if err = getMountInfo(); err != nil {
+ fi2, err := os.Stat(mnt.Path)
+ if err != nil {
return nil, err
}
-
- if mnt, ok := mountsByPath[mountpoint]; ok {
- return mnt, nil
+ if !os.SameFile(fi1, fi2) {
+ return nil, &ErrNotAMountpoint{mountpoint}
}
-
- return nil, errors.Wrap(ErrNotAMountpoint, mountpoint)
+ return mnt, nil
}
-// getMountsFromLink returns the Mount objects which match the provided link.
-// This link if formatted as a tag (e.g. <token>=<value>) similar to how they
-// apprear in "/etc/fstab". Currently, only "UUID" tokens are supported. Note
-// that this can match multiple Mounts (due to the existance of bind mounts). An
-// error is returned if the link is invalid or we cannot load the required mount
-// data. If a filesystem has been updated since the last call to one of the
-// mount functions, run UpdateMountInfo to see the change.
-func getMountsFromLink(link string) ([]*Mount, error) {
- // Parse the link
- linkComponents := strings.Split(link, "=")
- if len(linkComponents) != 2 {
- return nil, errors.Wrapf(ErrFollowLink, "link %q format in invalid", link)
- }
- token := linkComponents[0]
- value := linkComponents[1]
- if token != uuidToken {
- return nil, errors.Wrapf(ErrFollowLink, "token type %q not supported", token)
- }
-
- // See if UUID points to an existing device
- searchPath := filepath.Join(uuidDirectory, value)
- if filepath.Base(searchPath) != value {
- return nil, errors.Wrapf(ErrFollowLink, "value %q is not a UUID", value)
- }
- devicePath, err := cannonicalizePath(searchPath)
- if err != nil {
- return nil, errors.Wrapf(ErrFollowLink, "no device with UUID %q", value)
- }
+func uuidToDeviceNumber(uuid string) (DeviceNumber, error) {
+ uuidSymlinkPath := filepath.Join(uuidDirectory, uuid)
+ return getDeviceNumber(uuidSymlinkPath)
+}
- // Lookup mountpoints for device in global store
+func deviceNumberToMount(deviceNumber DeviceNumber) (*Mount, bool) {
mountMutex.Lock()
defer mountMutex.Unlock()
- if err := getMountInfo(); err != nil {
- return nil, err
- }
- mnts, ok := mountsByDevice[devicePath]
- if !ok {
- return nil, errors.Wrapf(ErrFollowLink, "no mounts for device %q", devicePath)
+ if err := loadMountInfo(); err != nil {
+ log.Print(err)
+ return nil, false
}
- return mnts, nil
+ mnt, ok := mountsByDevice[deviceNumber]
+ return mnt, ok
}
-// makeLink returns a link of the form <token>=<value> where value is the tag
-// value for the Mount's device. Currently, only "UUID" tokens are supported. An
-// error is returned if the mount has no device, or no UUID.
-func makeLink(mnt *Mount, token string) (string, error) {
- if token != uuidToken {
- return "", errors.Wrapf(ErrMakeLink, "token type %q not supported", token)
+// getMountFromLink returns the main Mount, if any, for the filesystem which the
+// given link points to. The link should contain a series of token-value pairs
+// (<token>=<value>), one per line. The supported tokens are "UUID" and "PATH".
+// If the UUID is present and it works, then it is used; otherwise, PATH is used
+// if it is present. (The fallback from UUID to PATH will keep the link working
+// if the UUID of the target filesystem changes but its mountpoint doesn't.)
+//
+// If a mount has been updated since the last call to one of the mount
+// functions, make sure to run UpdateMountInfo first.
+func getMountFromLink(link string) (*Mount, error) {
+ // Parse the link.
+ uuid := ""
+ path := ""
+ lines := strings.Split(link, "\n")
+ for _, line := range lines {
+ line := strings.TrimSpace(line)
+ if line == "" {
+ continue
+ }
+ pair := strings.Split(line, "=")
+ if len(pair) != 2 {
+ log.Printf("ignoring invalid line in filesystem link file: %q", line)
+ continue
+ }
+ token := pair[0]
+ value := pair[1]
+ switch token {
+ case uuidToken:
+ uuid = value
+ case pathToken:
+ path = value
+ default:
+ log.Printf("ignoring unknown link token %q", token)
+ }
+ }
+ // At least one of UUID and PATH must be present.
+ if uuid == "" && path == "" {
+ return nil, &ErrFollowLink{link, errors.Errorf("invalid filesystem link file")}
+ }
+
+ // Try following the UUID.
+ errMsg := ""
+ if uuid != "" {
+ deviceNumber, err := uuidToDeviceNumber(uuid)
+ if err == nil {
+ mnt, ok := deviceNumberToMount(deviceNumber)
+ if mnt != nil {
+ log.Printf("resolved filesystem link using UUID %q", uuid)
+ return mnt, nil
+ }
+ if ok {
+ return nil, &ErrFollowLink{link, filesystemLacksMainMountError(deviceNumber)}
+ }
+ log.Printf("cannot find filesystem with UUID %q", uuid)
+ } else {
+ log.Printf("cannot find filesystem with UUID %q: %v", uuid, err)
+ }
+ errMsg += fmt.Sprintf("cannot find filesystem with UUID %q", uuid)
+ if path != "" {
+ log.Printf("falling back to using mountpoint path instead of UUID")
+ }
}
- if mnt.Device == "" {
- return "", errors.Wrapf(ErrMakeLink, "no device for mount %q", mnt.Path)
+ // UUID didn't work. As a fallback, try the mountpoint path.
+ if path != "" {
+ mnt, err := GetMount(path)
+ if mnt != nil {
+ log.Printf("resolved filesystem link using mountpoint path %q", path)
+ return mnt, nil
+ }
+ log.Print(err)
+ if errMsg == "" {
+ errMsg = fmt.Sprintf("cannot find filesystem with main mountpoint %q", path)
+ } else {
+ errMsg += fmt.Sprintf(" or main mountpoint %q", path)
+ }
}
+ // No method worked; return an error.
+ return nil, &ErrFollowLink{link, errors.New(errMsg)}
+}
- dirContents, err := ioutil.ReadDir(uuidDirectory)
+func (mnt *Mount) getFilesystemUUID() (string, error) {
+ dirEntries, err := os.ReadDir(uuidDirectory)
if err != nil {
- return "", errors.Wrap(ErrMakeLink, err.Error())
+ return "", err
}
- for _, fileInfo := range dirContents {
+ for _, dirEntry := range dirEntries {
+ fileInfo, err := dirEntry.Info()
+ if err != nil {
+ continue
+ }
if fileInfo.Mode()&os.ModeSymlink == 0 {
continue // Only interested in UUID symlinks
}
uuid := fileInfo.Name()
- devicePath, err := cannonicalizePath(filepath.Join(uuidDirectory, uuid))
+ deviceNumber, err := uuidToDeviceNumber(uuid)
if err != nil {
log.Print(err)
continue
}
- if mnt.Device == devicePath {
- return fmt.Sprintf("%s=%s", uuidToken, uuid), nil
+ if mnt.DeviceNumber == deviceNumber {
+ return uuid, nil
}
}
- return "", errors.Wrapf(ErrMakeLink, "device %q has no UUID", mnt.Device)
+ return "", errors.Errorf("cannot determine UUID of device %q (%v)",
+ mnt.Device, mnt.DeviceNumber)
+}
+
+// makeLink creates the contents of a link file which will point to the given
+// filesystem. This will normally be a string of the form
+// "UUID=<uuid>\nPATH=<path>\n". If the UUID cannot be determined, the UUID
+// portion will be omitted.
+func makeLink(mnt *Mount) (string, error) {
+ uuid, err := mnt.getFilesystemUUID()
+ if err != nil {
+ // The UUID could not be determined. This happens for btrfs
+ // filesystems, as the device number found via
+ // /dev/disk/by-uuid/* for btrfs filesystems differs from the
+ // actual device number of the mounted filesystem. Just rely
+ // entirely on the fallback to mountpoint path.
+ log.Print(err)
+ return fmt.Sprintf("%s=%s\n", pathToken, mnt.Path), nil
+ }
+ return fmt.Sprintf("%s=%s\n%s=%s\n", uuidToken, uuid, pathToken, mnt.Path), nil
}
generated by cgit v1.2.3 (git 2.25.1) at 2026-05-10 15:58:41 +0000