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copy.go
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copy.go
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// +build linux
package copy
/*
#include <linux/fs.h>
#ifndef FICLONE
#define FICLONE _IOW(0x94, 9, int)
#endif
*/
import "C"
import (
"container/list"
"fmt"
"io"
"os"
"path/filepath"
"syscall"
"time"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/system"
rsystem "github.com/opencontainers/runc/libcontainer/system"
"golang.org/x/sys/unix"
)
// Mode indicates whether to use hardlink or copy content
type Mode int
const (
// Content creates a new file, and copies the content of the file
Content Mode = iota
// Hardlink creates a new hardlink to the existing file
Hardlink
)
func copyRegular(srcPath, dstPath string, fileinfo os.FileInfo, copyWithFileRange, copyWithFileClone *bool) error {
srcFile, err := os.Open(srcPath)
if err != nil {
return err
}
defer srcFile.Close()
// If the destination file already exists, we shouldn't blow it away
dstFile, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, fileinfo.Mode())
if err != nil {
return err
}
defer dstFile.Close()
if *copyWithFileClone {
_, _, err = unix.Syscall(unix.SYS_IOCTL, dstFile.Fd(), C.FICLONE, srcFile.Fd())
if err == nil {
return nil
}
*copyWithFileClone = false
if err == unix.EXDEV {
*copyWithFileRange = false
}
}
if *copyWithFileRange {
err = doCopyWithFileRange(srcFile, dstFile, fileinfo)
// Trying the file_clone may not have caught the exdev case
// as the ioctl may not have been available (therefore EINVAL)
if err == unix.EXDEV || err == unix.ENOSYS {
*copyWithFileRange = false
} else {
return err
}
}
return legacyCopy(srcFile, dstFile)
}
func doCopyWithFileRange(srcFile, dstFile *os.File, fileinfo os.FileInfo) error {
amountLeftToCopy := fileinfo.Size()
for amountLeftToCopy > 0 {
n, err := unix.CopyFileRange(int(srcFile.Fd()), nil, int(dstFile.Fd()), nil, int(amountLeftToCopy), 0)
if err != nil {
return err
}
amountLeftToCopy = amountLeftToCopy - int64(n)
}
return nil
}
func legacyCopy(srcFile io.Reader, dstFile io.Writer) error {
_, err := pools.Copy(dstFile, srcFile)
return err
}
func copyXattr(srcPath, dstPath, attr string) error {
data, err := system.Lgetxattr(srcPath, attr)
if err != nil {
return err
}
if data != nil {
if err := system.Lsetxattr(dstPath, attr, data, 0); err != nil {
return err
}
}
return nil
}
type fileID struct {
dev uint64
ino uint64
}
type dirMtimeInfo struct {
dstPath *string
stat *syscall.Stat_t
}
// DirCopy copies or hardlinks the contents of one directory to another,
// properly handling xattrs, and soft links
//
// Copying xattrs can be opted out of by passing false for copyXattrs.
func DirCopy(srcDir, dstDir string, copyMode Mode, copyXattrs bool) error {
copyWithFileRange := true
copyWithFileClone := true
// This is a map of source file inodes to dst file paths
copiedFiles := make(map[fileID]string)
dirsToSetMtimes := list.New()
err := filepath.Walk(srcDir, func(srcPath string, f os.FileInfo, err error) error {
if err != nil {
return err
}
// Rebase path
relPath, err := filepath.Rel(srcDir, srcPath)
if err != nil {
return err
}
dstPath := filepath.Join(dstDir, relPath)
if err != nil {
return err
}
stat, ok := f.Sys().(*syscall.Stat_t)
if !ok {
return fmt.Errorf("Unable to get raw syscall.Stat_t data for %s", srcPath)
}
isHardlink := false
switch f.Mode() & os.ModeType {
case 0: // Regular file
id := fileID{dev: stat.Dev, ino: stat.Ino}
if copyMode == Hardlink {
isHardlink = true
if err2 := os.Link(srcPath, dstPath); err2 != nil {
return err2
}
} else if hardLinkDstPath, ok := copiedFiles[id]; ok {
if err2 := os.Link(hardLinkDstPath, dstPath); err2 != nil {
return err2
}
} else {
if err2 := copyRegular(srcPath, dstPath, f, ©WithFileRange, ©WithFileClone); err2 != nil {
return err2
}
copiedFiles[id] = dstPath
}
case os.ModeDir:
if err := os.Mkdir(dstPath, f.Mode()); err != nil && !os.IsExist(err) {
return err
}
case os.ModeSymlink:
link, err := os.Readlink(srcPath)
if err != nil {
return err
}
if err := os.Symlink(link, dstPath); err != nil {
return err
}
case os.ModeNamedPipe:
fallthrough
case os.ModeSocket:
if rsystem.RunningInUserNS() {
// cannot create a device if running in user namespace
return nil
}
if err := unix.Mkfifo(dstPath, stat.Mode); err != nil {
return err
}
case os.ModeDevice:
if err := unix.Mknod(dstPath, stat.Mode, int(stat.Rdev)); err != nil {
return err
}
default:
return fmt.Errorf("unknown file type for %s", srcPath)
}
// Everything below is copying metadata from src to dst. All this metadata
// already shares an inode for hardlinks.
if isHardlink {
return nil
}
if err := os.Lchown(dstPath, int(stat.Uid), int(stat.Gid)); err != nil {
return err
}
if copyXattrs {
if err := doCopyXattrs(srcPath, dstPath); err != nil {
return err
}
}
isSymlink := f.Mode()&os.ModeSymlink != 0
// There is no LChmod, so ignore mode for symlink. Also, this
// must happen after chown, as that can modify the file mode
if !isSymlink {
if err := os.Chmod(dstPath, f.Mode()); err != nil {
return err
}
}
// system.Chtimes doesn't support a NOFOLLOW flag atm
// nolint: unconvert
if f.IsDir() {
dirsToSetMtimes.PushFront(&dirMtimeInfo{dstPath: &dstPath, stat: stat})
} else if !isSymlink {
aTime := time.Unix(int64(stat.Atim.Sec), int64(stat.Atim.Nsec))
mTime := time.Unix(int64(stat.Mtim.Sec), int64(stat.Mtim.Nsec))
if err := system.Chtimes(dstPath, aTime, mTime); err != nil {
return err
}
} else {
ts := []syscall.Timespec{stat.Atim, stat.Mtim}
if err := system.LUtimesNano(dstPath, ts); err != nil {
return err
}
}
return nil
})
if err != nil {
return err
}
for e := dirsToSetMtimes.Front(); e != nil; e = e.Next() {
mtimeInfo := e.Value.(*dirMtimeInfo)
ts := []syscall.Timespec{mtimeInfo.stat.Atim, mtimeInfo.stat.Mtim}
if err := system.LUtimesNano(*mtimeInfo.dstPath, ts); err != nil {
return err
}
}
return nil
}
func doCopyXattrs(srcPath, dstPath string) error {
if err := copyXattr(srcPath, dstPath, "security.capability"); err != nil {
return err
}
// We need to copy this attribute if it appears in an overlay upper layer, as
// this function is used to copy those. It is set by overlay if a directory
// is removed and then re-created and should not inherit anything from the
// same dir in the lower dir.
if err := copyXattr(srcPath, dstPath, "trusted.overlay.opaque"); err != nil {
return err
}
return nil
}