Revert "Merge pull request #2053 from calmh/atomicwriter" (fixes #2058)

This reverts commit b611f72e0829f60f3410e6f07652794f437d35ad, reversing
changes made to a04b005e932244aa12882dfb95443df0c182163f.

cmd/syncthing/gui_csrf.go

@@ -12,6 +12,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/syncthing/syncthing/internal/osutil"
 	"github.com/syncthing/syncthing/internal/sync"
@@ -90,20 +91,28 @@ func newCsrfToken() string {
 }
 
 func saveCsrfTokens() {
-	// We're ignoring errors in here. It's not super critical and there's
-	// nothing relevant we can do about them anyway...
-
 	name := locations[locCsrfTokens]
-	f, err := osutil.CreateAtomic(name, 0600)
+	tmp := fmt.Sprintf("%s.tmp.%d", name, time.Now().UnixNano())
+
+	f, err := os.OpenFile(tmp, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644)
 	if err != nil {
 		return
 	}
+	defer os.Remove(tmp)
 
 	for _, t := range csrfTokens {
-		fmt.Fprintln(f, t)
+		_, err := fmt.Fprintln(f, t)
+		if err != nil {
+			return
+		}
+	}
+
+	err = f.Close()
+	if err != nil {
+		return
 	}
 
-	f.Close()
+	osutil.Rename(tmp, name)
 }
 
 func loadCsrfTokens() {

internal/config/wrapper.go

@@ -7,7 +7,9 @@
 package config
 
 import (
+	"io/ioutil"
 	"os"
+	"path/filepath"
 
 	"github.com/syncthing/protocol"
 	"github.com/syncthing/syncthing/internal/events"
@@ -281,20 +283,24 @@ func (w *Wrapper) IgnoredDevice(id protocol.DeviceID) bool {
 
 // Save writes the configuration to disk, and generates a ConfigSaved event.
 func (w *Wrapper) Save() error {
-	fd, err := osutil.CreateAtomic(w.path, 0600)
+	fd, err := ioutil.TempFile(filepath.Dir(w.path), "cfg")
 	if err != nil {
 		return err
 	}
+	defer os.Remove(fd.Name())
 
-	if err := w.cfg.WriteXML(fd); err != nil {
+	err = w.cfg.WriteXML(fd)
+	if err != nil {
 		fd.Close()
 		return err
 	}
 
-	if err := fd.Close(); err != nil {
+	err = fd.Close()
+	if err != nil {
 		return err
 	}
 
 	events.Default.Log(events.ConfigSaved, w.cfg)
-	return nil
+
+	return osutil.Rename(fd.Name(), w.path)
 }

internal/model/model.go

@@ -13,6 +13,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"net"
 	"os"
 	"path/filepath"
@@ -935,17 +936,30 @@ func (m *Model) SetIgnores(folder string, content []string) error {
 		return fmt.Errorf("Folder %s does not exist", folder)
 	}
 
-	fd, err := osutil.CreateAtomic(filepath.Join(cfg.Path(), ".stignore"), 0644)
+	fd, err := ioutil.TempFile(cfg.Path(), ".syncthing.stignore-"+folder)
 	if err != nil {
 		l.Warnln("Saving .stignore:", err)
 		return err
 	}
+	defer os.Remove(fd.Name())
 
 	for _, line := range content {
-		fmt.Fprintln(fd, line)
+		_, err = fmt.Fprintln(fd, line)
+		if err != nil {
+			l.Warnln("Saving .stignore:", err)
+			return err
+		}
+	}
+
+	err = fd.Close()
+	if err != nil {
+		l.Warnln("Saving .stignore:", err)
+		return err
 	}
 
-	if err := fd.Close(); err != nil {
+	file := filepath.Join(cfg.Path(), ".stignore")
+	err = osutil.Rename(fd.Name(), file)
+	if err != nil {
 		l.Warnln("Saving .stignore:", err)
 		return err
 	}

internal/osutil/atomic.go

@@ -1,90 +0,0 @@
-// Copyright (C) 2015 The Syncthing Authors.
-//
-// This Source Code Form is subject to the terms of the Mozilla Public
-// License, v. 2.0. If a copy of the MPL was not distributed with this file,
-// You can obtain one at http://mozilla.org/MPL/2.0/.
-
-package osutil
-
-import (
-	"errors"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-)
-
-var (
-	ErrClosed  = errors.New("write to closed writer")
-	TempPrefix = ".syncthing.tmp."
-)
-
-// An AtomicWriter is an *os.File that writes to a temporary file in the same
-// directory as the final path. On successfull Close the file is renamed to
-// it's final path. Any error on Write or during Close is accumulated and
-// returned on Close, so a lazy user can ignore errors until Close.
-type AtomicWriter struct {
-	path string
-	next *os.File
-	err  error
-}
-
-// CreateAtomic is like os.Create with a FileMode, except a temporary file
-// name is used instead of the given name.
-func CreateAtomic(path string, mode os.FileMode) (*AtomicWriter, error) {
-	fd, err := ioutil.TempFile(filepath.Dir(path), TempPrefix)
-	if err != nil {
-		return nil, err
-	}
-
-	if err := os.Chmod(fd.Name(), mode); err != nil {
-		fd.Close()
-		os.Remove(fd.Name())
-		return nil, err
-	}
-
-	w := &AtomicWriter{
-		path: path,
-		next: fd,
-	}
-
-	return w, nil
-}
-
-// Write is like io.Writer, but is a no-op on an already failed AtomicWriter.
-func (w *AtomicWriter) Write(bs []byte) (int, error) {
-	if w.err != nil {
-		return 0, w.err
-	}
-	n, err := w.next.Write(bs)
-	if err != nil {
-		w.err = err
-		w.next.Close()
-	}
-	return n, err
-}
-
-// Close closes the temporary file and renames it to the final path. It is
-// invalid to call Write() or Close() after Close().
-func (w *AtomicWriter) Close() error {
-	if w.err != nil {
-		return w.err
-	}
-
-	// Try to not leave temp file around, but ignore error.
-	defer os.Remove(w.next.Name())
-
-	if err := w.next.Close(); err != nil {
-		w.err = err
-		return err
-	}
-
-	if err := os.Rename(w.next.Name(), w.path); err != nil {
-		w.err = err
-		return err
-	}
-
-	// Set w.err to return appropriately for any future operations.
-	w.err = ErrClosed
-
-	return nil
-}

internal/osutil/atomic_test.go

@@ -1,52 +0,0 @@
-// Copyright (C) 2015 The Syncthing Authors.
-//
-// This Source Code Form is subject to the terms of the Mozilla Public
-// License, v. 2.0. If a copy of the MPL was not distributed with this file,
-// You can obtain one at http://mozilla.org/MPL/2.0/.
-
-package osutil
-
-import (
-	"bytes"
-	"io/ioutil"
-	"os"
-	"testing"
-)
-
-func TestCreateAtomic(t *testing.T) {
-	os.RemoveAll("testdata")
-	defer os.RemoveAll("testdata")
-
-	if err := os.Mkdir("testdata", 0755); err != nil {
-		t.Fatal(err)
-	}
-
-	w, err := CreateAtomic("testdata/file", 0644)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	n, err := w.Write([]byte("hello"))
-	if err != nil {
-		t.Fatal(err)
-	}
-	if n != 5 {
-		t.Fatal("written bytes", n, "!= 5")
-	}
-
-	if _, err := ioutil.ReadFile("testdata/file"); err == nil {
-		t.Fatal("file should not exist")
-	}
-
-	if err := w.Close(); err != nil {
-		t.Fatal(err)
-	}
-
-	bs, err := ioutil.ReadFile("testdata/file")
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !bytes.Equal(bs, []byte("hello")) {
-		t.Error("incorrect data")
-	}
-}