Merge pull request #65997 from tallclair/writer

Automatic merge from submit-queue (batch tested with PRs 66030, 65997). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Remove unused io util writer & volume host GetWriter()

Cleanup unused code.
Fixes https://github.com/kubernetes/kubernetes/issues/16971

**Release note**:
```release-note
NONE
```

/kind cleanup
/sig storage

pkg/util/io/BUILD

@@ -7,15 +7,8 @@ load(
 
 go_library(
     name = "go_default_library",
-    srcs = [
-        "consistentread.go",
-        "writer.go",
-    ],
+    srcs = ["consistentread.go"],
     importpath = "k8s.io/kubernetes/pkg/util/io",
-    deps = [
-        "//pkg/util/nsenter:go_default_library",
-        "//vendor/github.com/golang/glog:go_default_library",
-    ],
 )
 
 filegroup(

pkg/util/io/writer.go

@@ -1,87 +0,0 @@
-/*
-Copyright 2015 The Kubernetes 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 io
-
-import (
-	"bytes"
-	"fmt"
-	"io/ioutil"
-	"os"
-
-	"k8s.io/kubernetes/pkg/util/nsenter"
-
-	"github.com/golang/glog"
-)
-
-// Writer is an interface which allows to write data to a file.
-type Writer interface {
-	// WriteFile mimics ioutil.WriteFile.
-	WriteFile(filename string, data []byte, perm os.FileMode) error
-}
-
-// StdWriter implements Writer interface and uses standard libraries
-// for writing data to files.
-type StdWriter struct {
-}
-
-// WriteFile directly calls ioutil.WriteFile.
-func (writer *StdWriter) WriteFile(filename string, data []byte, perm os.FileMode) error {
-	return ioutil.WriteFile(filename, data, perm)
-}
-
-// NsenterWriter is implementation of Writer interface that allows writing data
-// to file using nsenter command.
-// If a program (e.g. kubelet) runs in a container it may want to write data to
-// a mounted device. Since in Docker, mount propagation mode is set to private,
-// it will not see the mounted device in its own namespace. To work around this
-// limitation one has to first enter hosts namespace (by using 'nsenter') and
-// only then write data.
-type NsenterWriter struct {
-	ne *nsenter.Nsenter
-}
-
-// NewNsenterWriter creates a new Writer that allows writing data to file using
-// nsenter command.
-func NewNsenterWriter(ne *nsenter.Nsenter) *NsenterWriter {
-	return &NsenterWriter{
-		ne: ne,
-	}
-}
-
-// WriteFile calls 'nsenter cat - > <the file>' and 'nsenter chmod' to create a
-// file on the host.
-func (writer *NsenterWriter) WriteFile(filename string, data []byte, perm os.FileMode) error {
-	echoArgs := []string{"-c", fmt.Sprintf("cat > %s", filename)}
-	glog.V(5).Infof("nsenter: write data to file %s by nsenter", filename)
-	command := writer.ne.Exec("sh", echoArgs)
-	command.SetStdin(bytes.NewBuffer(data))
-	outputBytes, err := command.CombinedOutput()
-	if err != nil {
-		glog.Errorf("Output from writing to %q: %v", filename, string(outputBytes))
-		return err
-	}
-
-	chmodArgs := []string{fmt.Sprintf("%o", perm), filename}
-	glog.V(5).Infof("nsenter: change permissions of file %s to %s", filename, chmodArgs[0])
-	outputBytes, err = writer.ne.Exec("chmod", chmodArgs).CombinedOutput()
-	if err != nil {
-		glog.Errorf("Output from chmod command: %v", string(outputBytes))
-		return err
-	}
-
-	return nil
-}