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dummy driver: Use cp --reflink=auto to copy directories

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On systems that supports reflinking (i.e. btrfs) this means the dummy
backend is much faster at copying files and will be sharing file data in
a CoW fashion.

On my (btrfs) system this makes "docker run ubuntu echo hello world" go
from about 3 seconds to about 1 second. Not instant, but clearly better.

cp --reflink=auto is availible since coreutils 7.5 (around 2009), so this
seems pretty ok to rely on.

cp is also better at preserving file metadata than tar, so for instance
it will copy xattrs.
This commit is contained in:
Alexander Larsson 2013-11-19 13:09:36 +01:00
parent e42b574579
commit 242fd4b3ef
1 changed files with 10 additions and 2 deletions
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12
graphdriver/dummy/driver.go
View file

@ -2,9 +2,9 @@ package dummy
import (
"fmt"
"github.com/dotcloud/docker/archive"
"github.com/dotcloud/docker/graphdriver"
"os"
"os/exec"
"path"
)
@ -35,6 +35,14 @@ func (d *Driver) Cleanup() error {
return nil
}
func copyDir(src, dst string) error {
cmd := exec.Command("cp", "-aT", "--reflink=auto", src, dst)
if err := cmd.Run(); err != nil {
return err
}
return nil
}
func (d *Driver) Create(id string, parent string) error {
dir := d.dir(id)
if err := os.MkdirAll(path.Dir(dir), 0700); err != nil {
@ -50,7 +58,7 @@ func (d *Driver) Create(id string, parent string) error {
if err != nil {
return fmt.Errorf("%s: %s", parent, err)
}
if err := archive.CopyWithTar(parentDir, dir); err != nil {
if err := copyDir(parentDir, dir); err != nil {
return err
}
return nil