Next iteration

Signed-off-by: Tom Wieczorek <[email protected]>

go.mod

@@ -53,6 +53,7 @@ require (
 	go.etcd.io/etcd/etcdutl/v3 v3.5.16
 	go.uber.org/zap v1.27.0
 	golang.org/x/crypto v0.28.0
+	golang.org/x/exp v0.0.0-20230905200255-921286631fa9
 	golang.org/x/mod v0.21.0
 	golang.org/x/sync v0.8.0
 	golang.org/x/sys v0.26.0
@@ -257,7 +258,6 @@ require (
 	go.opentelemetry.io/proto/otlp v1.3.1 // indirect
 	go.starlark.net v0.0.0-20230525235612-a134d8f9ddca // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
 	golang.org/x/net v0.30.0 // indirect
 	golang.org/x/oauth2 v0.22.0 // indirect
 	golang.org/x/term v0.25.0 // indirect

internal/os/unix/dirfd_linux.go

@@ -31,12 +31,40 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// Opens the path with the given name by using the openat2 syscall.
+// An open Linux-native handle to some path on the file system.
+type LinuxPath interface {
+	Path
+
+	// Stats this path using the fstatat(path, "", AT_EMPTY_PATH) syscall.
+	StatSelf() (*FileInfo, error)
+}
+
+var _ LinuxPath = (*PathFD)(nil)
+
+// Stats this path using the fstatat(path, "", AT_EMPTY_PATH) syscall.
+func (p *PathFD) StatSelf() (*FileInfo, error) {
+	return p.UnwrapDir().StatSelf()
+}
+
+var _ LinuxPath = (*DirFD)(nil)
+
+// Stats this path using the fstatat(path, "", AT_EMPTY_PATH) syscall.
+func (d *DirFD) StatSelf() (*FileInfo, error) {
+	return d.StatAt("", unix.AT_EMPTY_PATH)
+}
+
+// Opens the path with the given name.
+// The path is opened relative to the receiver, using the openat2 syscall.
+//
+// Note that, in contrast to [os.Open] and [os.OpenFile], the returned
+// descriptor is not put into non-blocking mode automatically. Callers may
+// decide if they want this by setting the [syscall.O_NONBLOCK] flag.
+//
 // Available since Linux 5.6 (April 2020).
 //
 // https://www.man7.org/linux/man-pages/man2/openat2.2.html
 // https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fddb5d430ad9fa91b49b1d34d0202ffe2fa0e179
-func (d *DirFD) Open2(name string, how unix.OpenHow) (*DirFDEntry, error) {
+func (d *DirFD) Open2(name string, how unix.OpenHow) (*PathFD, error) {
 	var opened int
 	if err := openAt2Support.guard(func() error {
 		return syscallControl(d, func(fd uintptr) (err error) {
@@ -45,13 +73,13 @@ func (d *DirFD) Open2(name string, how unix.OpenHow) (*DirFDEntry, error) {
 			if err == nil {
 				return nil
 			}
-			return &os.PathError{Op: "openat2", Path: name, Err: err}
+			return pathErr("openat2", d, name, err)
 		})
 	}); err != nil {
 		return nil, err
 	}
 
-	return (*DirFDEntry)(os.NewFile(uintptr(opened), name)), nil
+	return (*PathFD)(os.NewFile(uintptr(opened), name)), nil
 }
 
 // Opens the directory with the given name by using the openat2 syscall.
@@ -60,7 +88,7 @@ func (d *DirFD) Open2(name string, how unix.OpenHow) (*DirFDEntry, error) {
 func (d *DirFD) OpenDir2(name string, how unix.OpenHow) (*DirFD, error) {
 	how.Flags |= unix.O_DIRECTORY
 	f, err := d.Open2(name, how)
-	return f.AsDir(), err
+	return f.UnwrapDir(), err
 }
 
 var openAt2Support = runtimeSupport{test: func() error {
@@ -75,7 +103,9 @@ var openAt2Support = runtimeSupport{test: func() error {
 	return nil
 }}
 
-// Stats the path with the given name by using the statx syscall.
+// Stats the path with the given name.
+// The path is interpreted relative to the receiver, using the statx syscall.
+//
 // Available since Linux 4.11 (May 2017).
 //
 // https://www.man7.org/linux/man-pages/man2/statx.2.html
@@ -84,7 +114,7 @@ func (d *DirFD) StatX(name string, flags, mask int) (*FileInfoX, error) {
 	const requiredMask = unix.STATX_MODE | unix.STATX_TYPE | unix.STATX_SIZE | unix.STATX_MTIME
 
 	info := FileInfoX{Path: name}
-	err := d.RawStatX(name, flags, mask|requiredMask, &info.StatX)
+	err := d.NativeStatX(name, flags, mask|requiredMask, &info.StatX)
 	if err != nil {
 		return nil, err
 	}
@@ -99,11 +129,9 @@ func (d *DirFD) StatX(name string, flags, mask int) (*FileInfoX, error) {
 	return &info, nil
 }
 
-// Stats the path with the given name by using the statx syscall, returning the
-// raw stats. Available since Linux 4.11 (May 2017).
-//
-// https://www.man7.org/linux/man-pages/man2/statx.2.html
-func (d *DirFD) RawStatX(name string, flags, mask int, stat *StatX) error {
+// Stats the path with the given name, just like [DirFD.StatX], but returning
+// stats in the native format of the operating system.
+func (d *DirFD) NativeStatX(name string, flags, mask int, stat *StatX) error {
 	return statxSupport.guard(func() error {
 		return syscallControl(d, func(fd uintptr) error {
 			err := unix.Statx(int(fd), name, flags, mask, (*unix.Statx_t)(stat))

internal/os/unix/dirfd_linux_test.go

@@ -0,0 +1,47 @@
+/*
+Copyright 2024 k0s authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package unix_test
+
+import (
+	"testing"
+
+	osunix "github.com/k0sproject/k0s/internal/os/unix"
+	"golang.org/x/sys/unix"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPathFD_StatSelf(t *testing.T) {
+	dirPath := t.TempDir()
+
+	p, err := osunix.OpenPath(dirPath, unix.O_PATH, 0)
+	require.NoError(t, err)
+	t.Cleanup(func() { assert.NoError(t, p.Close()) })
+
+	// An O_PATH descriptor cannot read anything.
+	_, err = p.UnwrapDir().Readdirnames(1)
+	assert.ErrorIs(t, err, unix.EBADF)
+
+	// Verify that the fstatat syscall works for O_PATH file descriptors.
+	// It's not documented in the Linux man pages, just fstat is.
+	// See open(2).
+	stat, err := p.StatSelf()
+	if assert.NoError(t, err) {
+		assert.True(t, stat.IsDir())
+	}
+}