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314 lines
7.5 KiB
Go
314 lines
7.5 KiB
Go
// +build linux
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package btrfs
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/*
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#include <stdlib.h>
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#include <dirent.h>
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#include <btrfs/ioctl.h>
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#include <btrfs/ctree.h>
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*/
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import "C"
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import (
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"fmt"
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"os"
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"path"
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"path/filepath"
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"syscall"
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"unsafe"
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"github.com/docker/docker/daemon/graphdriver"
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"github.com/docker/docker/pkg/idtools"
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"github.com/docker/docker/pkg/mount"
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"github.com/opencontainers/runc/libcontainer/label"
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)
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func init() {
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graphdriver.Register("btrfs", Init)
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}
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// Init returns a new BTRFS driver.
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// An error is returned if BTRFS is not supported.
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func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error) {
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rootdir := path.Dir(home)
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var buf syscall.Statfs_t
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if err := syscall.Statfs(rootdir, &buf); err != nil {
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return nil, err
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}
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if graphdriver.FsMagic(buf.Type) != graphdriver.FsMagicBtrfs {
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return nil, graphdriver.ErrPrerequisites
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}
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rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
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if err != nil {
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return nil, err
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}
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if err := idtools.MkdirAllAs(home, 0700, rootUID, rootGID); err != nil {
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return nil, err
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}
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if err := mount.MakePrivate(home); err != nil {
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return nil, err
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}
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driver := &Driver{
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home: home,
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uidMaps: uidMaps,
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gidMaps: gidMaps,
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}
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return graphdriver.NewNaiveDiffDriver(driver, uidMaps, gidMaps), nil
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}
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// Driver contains information about the filesystem mounted.
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type Driver struct {
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//root of the file system
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home string
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uidMaps []idtools.IDMap
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gidMaps []idtools.IDMap
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}
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// String prints the name of the driver (btrfs).
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func (d *Driver) String() string {
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return "btrfs"
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}
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// Status returns current driver information in a two dimensional string array.
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// Output contains "Build Version" and "Library Version" of the btrfs libraries used.
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// Version information can be used to check compatibility with your kernel.
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func (d *Driver) Status() [][2]string {
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status := [][2]string{}
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if bv := btrfsBuildVersion(); bv != "-" {
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status = append(status, [2]string{"Build Version", bv})
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}
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if lv := btrfsLibVersion(); lv != -1 {
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status = append(status, [2]string{"Library Version", fmt.Sprintf("%d", lv)})
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}
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return status
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}
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// GetMetadata returns empty metadata for this driver.
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func (d *Driver) GetMetadata(id string) (map[string]string, error) {
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return nil, nil
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}
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// Cleanup unmounts the home directory.
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func (d *Driver) Cleanup() error {
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return mount.Unmount(d.home)
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}
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func free(p *C.char) {
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C.free(unsafe.Pointer(p))
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}
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func openDir(path string) (*C.DIR, error) {
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Cpath := C.CString(path)
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defer free(Cpath)
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dir := C.opendir(Cpath)
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if dir == nil {
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return nil, fmt.Errorf("Can't open dir")
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}
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return dir, nil
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}
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func closeDir(dir *C.DIR) {
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if dir != nil {
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C.closedir(dir)
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}
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}
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func getDirFd(dir *C.DIR) uintptr {
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return uintptr(C.dirfd(dir))
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}
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func subvolCreate(path, name string) error {
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dir, err := openDir(path)
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if err != nil {
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return err
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}
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defer closeDir(dir)
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var args C.struct_btrfs_ioctl_vol_args
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for i, c := range []byte(name) {
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args.name[i] = C.char(c)
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}
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_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, getDirFd(dir), C.BTRFS_IOC_SUBVOL_CREATE,
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uintptr(unsafe.Pointer(&args)))
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if errno != 0 {
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return fmt.Errorf("Failed to create btrfs subvolume: %v", errno.Error())
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}
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return nil
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}
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func subvolSnapshot(src, dest, name string) error {
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srcDir, err := openDir(src)
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if err != nil {
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return err
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}
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defer closeDir(srcDir)
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destDir, err := openDir(dest)
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if err != nil {
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return err
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}
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defer closeDir(destDir)
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var args C.struct_btrfs_ioctl_vol_args_v2
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args.fd = C.__s64(getDirFd(srcDir))
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for i, c := range []byte(name) {
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args.name[i] = C.char(c)
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}
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_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, getDirFd(destDir), C.BTRFS_IOC_SNAP_CREATE_V2,
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uintptr(unsafe.Pointer(&args)))
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if errno != 0 {
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return fmt.Errorf("Failed to create btrfs snapshot: %v", errno.Error())
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}
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return nil
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}
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func isSubvolume(p string) (bool, error) {
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var bufStat syscall.Stat_t
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if err := syscall.Lstat(p, &bufStat); err != nil {
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return false, err
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}
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// return true if it is a btrfs subvolume
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return bufStat.Ino == C.BTRFS_FIRST_FREE_OBJECTID, nil
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}
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func subvolDelete(dirpath, name string) error {
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dir, err := openDir(dirpath)
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if err != nil {
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return err
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}
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defer closeDir(dir)
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fullPath := path.Join(dirpath, name)
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var args C.struct_btrfs_ioctl_vol_args
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// walk the btrfs subvolumes
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walkSubvolumes := func(p string, f os.FileInfo, err error) error {
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if err != nil {
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if os.IsNotExist(err) && p != fullPath {
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// missing most likely because the path was a subvolume that got removed in the previous iteration
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// since it's gone anyway, we don't care
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return nil
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}
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return fmt.Errorf("error walking subvolumes: %v", err)
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}
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// we want to check children only so skip itself
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// it will be removed after the filepath walk anyways
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if f.IsDir() && p != fullPath {
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sv, err := isSubvolume(p)
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if err != nil {
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return fmt.Errorf("Failed to test if %s is a btrfs subvolume: %v", p, err)
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}
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if sv {
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if err := subvolDelete(path.Dir(p), f.Name()); err != nil {
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return fmt.Errorf("Failed to destroy btrfs child subvolume (%s) of parent (%s): %v", p, dirpath, err)
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}
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}
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}
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return nil
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}
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if err := filepath.Walk(path.Join(dirpath, name), walkSubvolumes); err != nil {
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return fmt.Errorf("Recursively walking subvolumes for %s failed: %v", dirpath, err)
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}
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// all subvolumes have been removed
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// now remove the one originally passed in
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for i, c := range []byte(name) {
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args.name[i] = C.char(c)
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}
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_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, getDirFd(dir), C.BTRFS_IOC_SNAP_DESTROY,
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uintptr(unsafe.Pointer(&args)))
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if errno != 0 {
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return fmt.Errorf("Failed to destroy btrfs snapshot %s for %s: %v", dirpath, name, errno.Error())
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}
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return nil
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}
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func (d *Driver) subvolumesDir() string {
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return path.Join(d.home, "subvolumes")
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}
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func (d *Driver) subvolumesDirID(id string) string {
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return path.Join(d.subvolumesDir(), id)
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}
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// Create the filesystem with given id.
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func (d *Driver) Create(id, parent, mountLabel string) error {
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subvolumes := path.Join(d.home, "subvolumes")
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rootUID, rootGID, err := idtools.GetRootUIDGID(d.uidMaps, d.gidMaps)
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if err != nil {
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return err
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}
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if err := idtools.MkdirAllAs(subvolumes, 0700, rootUID, rootGID); err != nil {
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return err
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}
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if parent == "" {
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if err := subvolCreate(subvolumes, id); err != nil {
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return err
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}
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} else {
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parentDir, err := d.Get(parent, "")
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if err != nil {
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return err
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}
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if err := subvolSnapshot(parentDir, subvolumes, id); err != nil {
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return err
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}
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}
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return label.Relabel(path.Join(subvolumes, id), mountLabel, false)
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}
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// Remove the filesystem with given id.
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func (d *Driver) Remove(id string) error {
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dir := d.subvolumesDirID(id)
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if _, err := os.Stat(dir); err != nil {
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return err
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}
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if err := subvolDelete(d.subvolumesDir(), id); err != nil {
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return err
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}
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if err := os.RemoveAll(dir); err != nil && !os.IsNotExist(err) {
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return err
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}
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return nil
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}
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// Get the requested filesystem id.
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func (d *Driver) Get(id, mountLabel string) (string, error) {
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dir := d.subvolumesDirID(id)
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st, err := os.Stat(dir)
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if err != nil {
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return "", err
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}
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if !st.IsDir() {
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return "", fmt.Errorf("%s: not a directory", dir)
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}
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return dir, nil
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}
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// Put is not implemented for BTRFS as there is no cleanup required for the id.
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func (d *Driver) Put(id string) error {
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// Get() creates no runtime resources (like e.g. mounts)
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// so this doesn't need to do anything.
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return nil
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}
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// Exists checks if the id exists in the filesystem.
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func (d *Driver) Exists(id string) bool {
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dir := d.subvolumesDirID(id)
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_, err := os.Stat(dir)
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return err == nil
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}
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