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Add experimenta btrfs driver

This is an experimental btrfs driver. To use it you must have
/var/lib/docker mounted on a btrfs filesystem and explicitly
specify DOCKER_DRIVER=btrfs in the docker daemon environment.

It works by using subvolumes for the docker image/container layers.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
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alexlarsson committed Nov 21, 2013
1 parent 700db10 commit e51af36a85126aca6bf6da5291eaf960fd82aa56
Showing with 221 additions and 0 deletions.
  1. +215 −0 graphdriver/btrfs/btrfs.go
  2. +3 −0 graphdriver/btrfs/dummy_unsupported.go
  3. +2 −0 graphdriver/driver.go
  4. +1 −0 runtime.go
@@ -0,0 +1,215 @@
// +build linux
package btrfs
/*
#include <stdlib.h>
#include <sys/ioctl.h>
#include <linux/fs.h>
#include <errno.h>
#include <sys/types.h>
#include <dirent.h>
#include <linux/btrfs.h>
*/
import "C"
import (
"fmt"
"github.com/dotcloud/docker/graphdriver"
"os"
"path"
"syscall"
"unsafe"
)
func init() {
graphdriver.Register("btrfs", Init)
}
func Init(home string) (graphdriver.Driver, error) {
rootdir := path.Dir(home)
var buf syscall.Statfs_t
if err := syscall.Statfs(rootdir, &buf); err != nil {
return nil, err
}
if buf.Type != 0x9123683E {
return nil, fmt.Errorf("%s is not a btrfs filesystem", rootdir)
}
return &Driver{
home: home,
}, nil
}
type Driver struct {
home string
}
func (d *Driver) String() string {
return "btrfs"
}
func (d *Driver) Status() [][2]string {
return nil
}
func (d *Driver) Cleanup() error {
return nil
}
func free(p *C.char) {
C.free(unsafe.Pointer(p))
}
func openDir(path string) (*C.DIR, error) {
Cpath := C.CString(path)
defer free(Cpath)
dir := C.opendir(Cpath)
if dir == nil {
return nil, fmt.Errorf("Can't open dir")
}
return dir, nil
}
func closeDir(dir *C.DIR) {
if dir != nil {
C.closedir(dir)
}
}
func getDirFd(dir *C.DIR) uintptr {
return uintptr(C.dirfd(dir))
}
func subvolCreate(path, name string) error {
dir, err := openDir(path)
if err != nil {
return err
}
defer closeDir(dir)
var args C.struct_btrfs_ioctl_vol_args
for i, c := range []byte(name) {
args.name[i] = C.char(c)
}
_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, getDirFd(dir), C.BTRFS_IOC_SUBVOL_CREATE,
uintptr(unsafe.Pointer(&args)))
if errno != 0 {
return fmt.Errorf("Can't create subvolume")
}
return nil
}
func subvolSnapshot(src, dest, name string) error {
srcDir, err := openDir(src)
if err != nil {
return err
}
defer closeDir(srcDir)
destDir, err := openDir(dest)
if err != nil {
return err
}
defer closeDir(destDir)
var args C.struct_btrfs_ioctl_vol_args_v2
args.fd = C.__s64(getDirFd(srcDir))
for i, c := range []byte(name) {
args.name[i] = C.char(c)
}
_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, getDirFd(destDir), C.BTRFS_IOC_SNAP_CREATE_V2,
uintptr(unsafe.Pointer(&args)))
if errno != 0 {
return fmt.Errorf("Can't create subvolume")
}
return nil
}
func subvolDelete(path, name string) error {
dir, err := openDir(path)
if err != nil {
return err
}
defer closeDir(dir)
var args C.struct_btrfs_ioctl_vol_args
for i, c := range []byte(name) {
args.name[i] = C.char(c)
}
_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, getDirFd(dir), C.BTRFS_IOC_SNAP_DESTROY,
uintptr(unsafe.Pointer(&args)))
if errno != 0 {
return fmt.Errorf("Can't create subvolume")
}
return nil
}
func (d *Driver) subvolumesDir() string {
return path.Join(d.home, "subvolumes")
}
func (d *Driver) subvolumesDirId(id string) string {
return path.Join(d.subvolumesDir(), id)
}
func (d *Driver) Create(id string, parent string) error {
subvolumes := path.Join(d.home, "subvolumes")
if err := os.MkdirAll(subvolumes, 0700); err != nil {
return err
}
if parent == "" {
if err := subvolCreate(subvolumes, id); err != nil {
return err
}
} else {
parentDir, err := d.Get(parent)
if err != nil {
return err
}
if err := subvolSnapshot(parentDir, subvolumes, id); err != nil {
return err
}
}
return nil
}
func (d *Driver) Remove(id string) error {
dir := d.subvolumesDirId(id)
if _, err := os.Stat(dir); err != nil {
return err
}
if err := subvolDelete(d.subvolumesDir(), id); err != nil {
return err
}
return os.RemoveAll(dir)
}
func (d *Driver) Get(id string) (string, error) {
dir := d.subvolumesDirId(id)
st, err := os.Stat(dir)
if err != nil {
return "", err
}
if !st.IsDir() {
return "", fmt.Errorf("%s: not a directory", dir)
}
return dir, nil
}
func (d *Driver) Put(id string) {
}
func (d *Driver) Exists(id string) bool {
dir := d.subvolumesDirId(id)
_, err := os.Stat(dir)
return err == nil
}
@@ -0,0 +1,3 @@
// +build !linux
package btrfs
@@ -41,6 +41,8 @@ var (
"aufs",
"devicemapper",
"vfs",
// experimental, has to be enabled manually for now
"btrfs",
}
)
@@ -9,6 +9,7 @@ import (
"github.com/dotcloud/docker/execdriver/lxc"
"github.com/dotcloud/docker/graphdriver"
"github.com/dotcloud/docker/graphdriver/aufs"
_ "github.com/dotcloud/docker/graphdriver/btrfs"
_ "github.com/dotcloud/docker/graphdriver/devmapper"
_ "github.com/dotcloud/docker/graphdriver/vfs"
"github.com/dotcloud/docker/pkg/graphdb"

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