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copy.go
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copy.go
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// +build linux
package overlay
import (
"fmt"
"os"
"path/filepath"
"syscall"
"time"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/system"
)
type copyFlags int
const (
copyHardlink copyFlags = 1 << iota
)
func copyRegular(srcPath, dstPath string, mode os.FileMode) error {
srcFile, err := os.Open(srcPath)
if err != nil {
return err
}
defer srcFile.Close()
dstFile, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE, mode)
if err != nil {
return err
}
defer dstFile.Close()
_, 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
}
func copyDir(srcDir, dstDir string, flags copyFlags) error {
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
if flags©Hardlink != 0 {
isHardlink = true
if err := os.Link(srcPath, dstPath); err != nil {
return err
}
} else {
if err := copyRegular(srcPath, dstPath, f.Mode()); err != nil {
return err
}
}
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 err := syscall.Mkfifo(dstPath, stat.Mode); err != nil {
return err
}
case os.ModeDevice:
if err := syscall.Mknod(dstPath, stat.Mode, int(stat.Rdev)); err != nil {
return err
}
default:
return fmt.Errorf("Unknown file type for %s\n", 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 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
}
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
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
})
return err
}