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aufs.go
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aufs.go
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// +build linux
/*
aufs driver directory structure
.
├── layers // Metadata of layers
│ ├── 1
│ ├── 2
│ └── 3
├── diff // Content of the layer
│ ├── 1 // Contains layers that need to be mounted for the id
│ ├── 2
│ └── 3
└── mnt // Mount points for the rw layers to be mounted
├── 1
├── 2
└── 3
*/
package aufs
import (
"bufio"
"fmt"
"io/ioutil"
"os"
"os/exec"
"path"
"strings"
"sync"
"syscall"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/daemon/graphdriver"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/chrootarchive"
"github.com/docker/docker/pkg/directory"
"github.com/docker/docker/pkg/idtools"
mountpk "github.com/docker/docker/pkg/mount"
"github.com/docker/docker/pkg/stringid"
"github.com/opencontainers/runc/libcontainer/label"
)
var (
// ErrAufsNotSupported is returned if aufs is not supported by the host.
ErrAufsNotSupported = fmt.Errorf("AUFS was not found in /proc/filesystems")
incompatibleFsMagic = []graphdriver.FsMagic{
graphdriver.FsMagicBtrfs,
graphdriver.FsMagicAufs,
}
backingFs = "<unknown>"
enableDirpermLock sync.Once
enableDirperm bool
)
func init() {
graphdriver.Register("aufs", Init)
}
type data struct {
referenceCount int
path string
}
// Driver contains information about the filesystem mounted.
// root of the filesystem
// sync.Mutex to protect against concurrent modifications
// active maps mount id to the count
type Driver struct {
root string
uidMaps []idtools.IDMap
gidMaps []idtools.IDMap
sync.Mutex // Protects concurrent modification to active
active map[string]*data
}
// Init returns a new AUFS driver.
// An error is returned if AUFS is not supported.
func Init(root string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error) {
// Try to load the aufs kernel module
if err := supportsAufs(); err != nil {
return nil, graphdriver.ErrNotSupported
}
fsMagic, err := graphdriver.GetFSMagic(root)
if err != nil {
return nil, err
}
if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
backingFs = fsName
}
for _, magic := range incompatibleFsMagic {
if fsMagic == magic {
return nil, graphdriver.ErrIncompatibleFS
}
}
paths := []string{
"mnt",
"diff",
"layers",
}
a := &Driver{
root: root,
active: make(map[string]*data),
uidMaps: uidMaps,
gidMaps: gidMaps,
}
rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
if err != nil {
return nil, err
}
// Create the root aufs driver dir and return
// if it already exists
// If not populate the dir structure
if err := idtools.MkdirAllAs(root, 0755, rootUID, rootGID); err != nil {
if os.IsExist(err) {
return a, nil
}
return nil, err
}
if err := mountpk.MakePrivate(root); err != nil {
return nil, err
}
// Populate the dir structure
for _, p := range paths {
if err := idtools.MkdirAllAs(path.Join(root, p), 0755, rootUID, rootGID); err != nil {
return nil, err
}
}
return a, nil
}
// Return a nil error if the kernel supports aufs
// We cannot modprobe because inside dind modprobe fails
// to run
func supportsAufs() error {
// We can try to modprobe aufs first before looking at
// proc/filesystems for when aufs is supported
exec.Command("modprobe", "aufs").Run()
f, err := os.Open("/proc/filesystems")
if err != nil {
return err
}
defer f.Close()
s := bufio.NewScanner(f)
for s.Scan() {
if strings.Contains(s.Text(), "aufs") {
return nil
}
}
return ErrAufsNotSupported
}
func (a *Driver) rootPath() string {
return a.root
}
func (*Driver) String() string {
return "aufs"
}
// Status returns current information about the filesystem such as root directory, number of directories mounted, etc.
func (a *Driver) Status() [][2]string {
ids, _ := loadIds(path.Join(a.rootPath(), "layers"))
return [][2]string{
{"Root Dir", a.rootPath()},
{"Backing Filesystem", backingFs},
{"Dirs", fmt.Sprintf("%d", len(ids))},
{"Dirperm1 Supported", fmt.Sprintf("%v", useDirperm())},
}
}
// GetMetadata not implemented
func (a *Driver) GetMetadata(id string) (map[string]string, error) {
return nil, nil
}
// Exists returns true if the given id is registered with
// this driver
func (a *Driver) Exists(id string) bool {
if _, err := os.Lstat(path.Join(a.rootPath(), "layers", id)); err != nil {
return false
}
return true
}
// Create three folders for each id
// mnt, layers, and diff
func (a *Driver) Create(id, parent string) error {
if err := a.createDirsFor(id); err != nil {
return err
}
// Write the layers metadata
f, err := os.Create(path.Join(a.rootPath(), "layers", id))
if err != nil {
return err
}
defer f.Close()
if parent != "" {
ids, err := getParentIds(a.rootPath(), parent)
if err != nil {
return err
}
if _, err := fmt.Fprintln(f, parent); err != nil {
return err
}
for _, i := range ids {
if _, err := fmt.Fprintln(f, i); err != nil {
return err
}
}
}
a.active[id] = &data{}
return nil
}
func (a *Driver) createDirsFor(id string) error {
paths := []string{
"mnt",
"diff",
}
rootUID, rootGID, err := idtools.GetRootUIDGID(a.uidMaps, a.gidMaps)
if err != nil {
return err
}
for _, p := range paths {
if err := idtools.MkdirAllAs(path.Join(a.rootPath(), p, id), 0755, rootUID, rootGID); err != nil {
return err
}
}
return nil
}
// Remove will unmount and remove the given id.
func (a *Driver) Remove(id string) error {
// Protect the a.active from concurrent access
a.Lock()
defer a.Unlock()
m := a.active[id]
if m != nil {
if m.referenceCount > 0 {
return nil
}
// Make sure the dir is umounted first
if err := a.unmount(m); err != nil {
return err
}
}
tmpDirs := []string{
"mnt",
"diff",
}
// Atomically remove each directory in turn by first moving it out of the
// way (so that docker doesn't find it anymore) before doing removal of
// the whole tree.
for _, p := range tmpDirs {
realPath := path.Join(a.rootPath(), p, id)
tmpPath := path.Join(a.rootPath(), p, fmt.Sprintf("%s-removing", id))
if err := os.Rename(realPath, tmpPath); err != nil && !os.IsNotExist(err) {
return err
}
defer os.RemoveAll(tmpPath)
}
// Remove the layers file for the id
if err := os.Remove(path.Join(a.rootPath(), "layers", id)); err != nil && !os.IsNotExist(err) {
return err
}
return nil
}
// Get returns the rootfs path for the id.
// This will mount the dir at it's given path
func (a *Driver) Get(id, mountLabel string) (string, error) {
ids, err := getParentIds(a.rootPath(), id)
if err != nil {
if !os.IsNotExist(err) {
return "", err
}
ids = []string{}
}
// Protect the a.active from concurrent access
a.Lock()
defer a.Unlock()
m := a.active[id]
if m == nil {
m = &data{}
a.active[id] = m
}
// If a dir does not have a parent ( no layers )do not try to mount
// just return the diff path to the data
m.path = path.Join(a.rootPath(), "diff", id)
if len(ids) > 0 {
m.path = path.Join(a.rootPath(), "mnt", id)
if m.referenceCount == 0 {
if err := a.mount(id, m, mountLabel); err != nil {
return "", err
}
}
}
m.referenceCount++
return m.path, nil
}
// Put unmounts and updates list of active mounts.
func (a *Driver) Put(id string) error {
// Protect the a.active from concurrent access
a.Lock()
defer a.Unlock()
m := a.active[id]
if m == nil {
return nil
}
if count := m.referenceCount; count > 1 {
m.referenceCount = count - 1
} else {
ids, _ := getParentIds(a.rootPath(), id)
// We only mounted if there are any parents
if ids != nil && len(ids) > 0 {
a.unmount(m)
}
delete(a.active, id)
}
return nil
}
// Diff produces an archive of the changes between the specified
// layer and its parent layer which may be "".
func (a *Driver) Diff(id, parent string) (archive.Archive, error) {
// AUFS doesn't need the parent layer to produce a diff.
return archive.TarWithOptions(path.Join(a.rootPath(), "diff", id), &archive.TarOptions{
Compression: archive.Uncompressed,
ExcludePatterns: []string{archive.WhiteoutMetaPrefix + "*", "!" + archive.WhiteoutOpaqueDir},
UIDMaps: a.uidMaps,
GIDMaps: a.gidMaps,
})
}
func (a *Driver) applyDiff(id string, diff archive.Reader) error {
return chrootarchive.UntarUncompressed(diff, path.Join(a.rootPath(), "diff", id), &archive.TarOptions{
UIDMaps: a.uidMaps,
GIDMaps: a.gidMaps,
})
}
// DiffSize calculates the changes between the specified id
// and its parent and returns the size in bytes of the changes
// relative to its base filesystem directory.
func (a *Driver) DiffSize(id, parent string) (size int64, err error) {
// AUFS doesn't need the parent layer to calculate the diff size.
return directory.Size(path.Join(a.rootPath(), "diff", id))
}
// ApplyDiff extracts the changeset from the given diff into the
// layer with the specified id and parent, returning the size of the
// new layer in bytes.
func (a *Driver) ApplyDiff(id, parent string, diff archive.Reader) (size int64, err error) {
// AUFS doesn't need the parent id to apply the diff.
if err = a.applyDiff(id, diff); err != nil {
return
}
return a.DiffSize(id, parent)
}
// Changes produces a list of changes between the specified layer
// and its parent layer. If parent is "", then all changes will be ADD changes.
func (a *Driver) Changes(id, parent string) ([]archive.Change, error) {
// AUFS doesn't have snapshots, so we need to get changes from all parent
// layers.
layers, err := a.getParentLayerPaths(id)
if err != nil {
return nil, err
}
return archive.Changes(layers, path.Join(a.rootPath(), "diff", id))
}
func (a *Driver) getParentLayerPaths(id string) ([]string, error) {
parentIds, err := getParentIds(a.rootPath(), id)
if err != nil {
return nil, err
}
layers := make([]string, len(parentIds))
// Get the diff paths for all the parent ids
for i, p := range parentIds {
layers[i] = path.Join(a.rootPath(), "diff", p)
}
return layers, nil
}
func (a *Driver) mount(id string, m *data, mountLabel string) error {
// If the id is mounted or we get an error return
if mounted, err := a.mounted(m); err != nil || mounted {
return err
}
var (
target = m.path
rw = path.Join(a.rootPath(), "diff", id)
)
layers, err := a.getParentLayerPaths(id)
if err != nil {
return err
}
if err := a.aufsMount(layers, rw, target, mountLabel); err != nil {
return fmt.Errorf("error creating aufs mount to %s: %v", target, err)
}
return nil
}
func (a *Driver) unmount(m *data) error {
if mounted, err := a.mounted(m); err != nil || !mounted {
return err
}
return Unmount(m.path)
}
func (a *Driver) mounted(m *data) (bool, error) {
return mountpk.Mounted(m.path)
}
// Cleanup aufs and unmount all mountpoints
func (a *Driver) Cleanup() error {
for id, m := range a.active {
if err := a.unmount(m); err != nil {
logrus.Errorf("Unmounting %s: %s", stringid.TruncateID(id), err)
}
}
return mountpk.Unmount(a.root)
}
func (a *Driver) aufsMount(ro []string, rw, target, mountLabel string) (err error) {
defer func() {
if err != nil {
Unmount(target)
}
}()
// Mount options are clipped to page size(4096 bytes). If there are more
// layers then these are remounted individually using append.
offset := 54
if useDirperm() {
offset += len("dirperm1")
}
b := make([]byte, syscall.Getpagesize()-len(mountLabel)-offset) // room for xino & mountLabel
bp := copy(b, fmt.Sprintf("br:%s=rw", rw))
firstMount := true
i := 0
for {
for ; i < len(ro); i++ {
layer := fmt.Sprintf(":%s=ro+wh", ro[i])
if firstMount {
if bp+len(layer) > len(b) {
break
}
bp += copy(b[bp:], layer)
} else {
data := label.FormatMountLabel(fmt.Sprintf("append%s", layer), mountLabel)
if err = mount("none", target, "aufs", syscall.MS_REMOUNT, data); err != nil {
return
}
}
}
if firstMount {
opts := "dio,xino=/dev/shm/aufs.xino"
if useDirperm() {
opts += ",dirperm1"
}
data := label.FormatMountLabel(fmt.Sprintf("%s,%s", string(b[:bp]), opts), mountLabel)
if err = mount("none", target, "aufs", 0, data); err != nil {
return
}
firstMount = false
}
if i == len(ro) {
break
}
}
return
}
// useDirperm checks dirperm1 mount option can be used with the current
// version of aufs.
func useDirperm() bool {
enableDirpermLock.Do(func() {
base, err := ioutil.TempDir("", "docker-aufs-base")
if err != nil {
logrus.Errorf("error checking dirperm1: %v", err)
return
}
defer os.RemoveAll(base)
union, err := ioutil.TempDir("", "docker-aufs-union")
if err != nil {
logrus.Errorf("error checking dirperm1: %v", err)
return
}
defer os.RemoveAll(union)
opts := fmt.Sprintf("br:%s,dirperm1,xino=/dev/shm/aufs.xino", base)
if err := mount("none", union, "aufs", 0, opts); err != nil {
return
}
enableDirperm = true
if err := Unmount(union); err != nil {
logrus.Errorf("error checking dirperm1: failed to unmount %v", err)
}
})
return enableDirperm
}