Lchmod(): simplify and optimize

kolyshkin · kolyshkin · commit 9ab0ec639e27 · 2018-07-11T17:48:05.000-07:00
A quote from fchmodat(2) man page (this one is for Linux, others should be similar):

&gt; If pathname is relative and dirfd is the special value
&gt; AT_FDCWD, then pathname is interpreted relative to the current working
&gt; directory of the calling process (like chmod()).
&gt;
&gt; If pathname is absolute, then dirfd is ignored.

So, instead of calling filepath.Abs() let's use AT_FDCWD and let the
kernel figure things out for us.

While at it, fix the comment.

Signed-off-by: Kir Kolyshkin &lt;kolyshkin@gmail.com&gt;
diff --git a/driver/driver_unix.go b/driver/driver_unix.go
@@ -6,7 +6,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"path/filepath"
 	"sort"
 
 	"github.com/containerd/continuity/devices"
@@ -27,16 +26,9 @@ func (d *driver) Mkfifo(path string, mode os.FileMode) error {
 	return devices.Mknod(path, mode, 0, 0)
 }
 
-// Lchmod changes the mode of an file not following symlinks.
-func (d *driver) Lchmod(path string, mode os.FileMode) (err error) {
-	if !filepath.IsAbs(path) {
-		path, err = filepath.Abs(path)
-		if err != nil {
-			return
-		}
-	}
-
-	return unix.Fchmodat(0, path, uint32(mode), unix.AT_SYMLINK_NOFOLLOW)
+// Lchmod changes the mode of a file not following symlinks.
+func (d *driver) Lchmod(path string, mode os.FileMode) error {
+	return unix.Fchmodat(unix.AT_FDCWD, path, uint32(mode), unix.AT_SYMLINK_NOFOLLOW)
 }
 
 // Getxattr returns all of the extended attributes for the file at path p.
