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// Copyright 2015 Google Inc. All Rights Reserved.
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package fuse
import (
// Optional configuration accepted by Mount.
type MountConfig struct {
// The context from which every op read from the connetion by the sever
// should inherit. If nil, context.Background() will be used.
OpContext context.Context
// If non-empty, the name of the file system as displayed by e.g. `mount`.
// This is important because the `umount` command requires root privileges if
// it doesn't agree with /etc/fstab.
FSName string
// Mount the file system in read-only mode. File modes will appear as normal,
// but opening a file for writing and metadata operations like chmod,
// chtimes, etc. will fail.
ReadOnly bool
// A logger to use for logging errors. All errors are logged, with the
// exception of a few blacklisted errors that are expected. If nil, no error
// logging is performed.
ErrorLogger *log.Logger
// A logger to use for logging debug information. If nil, no debug logging is
// performed.
DebugLogger *log.Logger
// OS X only.
// Normally on OS X we mount with the novncache option
// (cf. http://goo.gl/1pTjuk), which disables entry caching in the kernel.
// This is because osxfuse does not honor the entry expiration values we
// return to it, instead caching potentially forever (cf.
// http://goo.gl/8yR0Ie), and it is probably better to fail to cache than to
// cache for too long, since the latter is more likely to hide consistency
// bugs that are difficult to detect and diagnose.
// This field disables the use of novncache, restoring entry caching. Beware:
// the value of ChildInodeEntry.EntryExpiration is ignored by the kernel, and
// entries will be cached for an arbitrarily long time.
EnableVnodeCaching bool
// Additional key=value options to pass unadulterated to the underlying mount
// command. See `man 8 mount`, the fuse documentation, etc. for
// system-specific information.
// For expert use only! May invalidate other guarantees made in the
// documentation for this package.
Options map[string]string
// Create a map containing all of the key=value mount options to be given to
// the mount helper.
func (c *MountConfig) toMap() (opts map[string]string) {
isDarwin := runtime.GOOS == "darwin"
opts = make(map[string]string)
// Enable permissions checking in the kernel. See the comments on
// InodeAttributes.Mode.
opts["default_permissions"] = ""
// HACK(jacobsa): Work around what appears to be a bug in systemd v219, as
// shipped in Ubuntu 15.04, where it automatically unmounts any file system
// that doesn't set an explicit name.
// When Ubuntu contains systemd v220, this workaround should be removed and
// the systemd bug reopened if the problem persists.
// Cf. https://github.com/bazil/fuse/issues/89
// Cf. https://bugs.freedesktop.org/show_bug.cgi?id=90907
fsname := c.FSName
if runtime.GOOS == "linux" && fsname == "" {
fsname = "some_fuse_file_system"
// Special file system name?
if fsname != "" {
opts["fsname"] = fsname
// Read only?
if c.ReadOnly {
opts["ro"] = ""
// OS X: set novncache when appropriate.
if isDarwin && !c.EnableVnodeCaching {
opts["novncache"] = ""
// OS X: disable the use of "Apple Double" (._foo and .DS_Store) files, which
// just add noise to debug output and can have significant cost on
// network-based file systems.
// Cf. https://github.com/osxfuse/osxfuse/wiki/Mount-options
if isDarwin {
opts["noappledouble"] = ""
// Last but not least: other user-supplied options.
for k, v := range c.Options {
opts[k] = v
func escapeOptionsKey(s string) (res string) {
res = s
res = strings.Replace(res, `\`, `\\`, -1)
res = strings.Replace(res, `,`, `\,`, -1)
// Create an options string suitable for passing to the mount helper.
func (c *MountConfig) toOptionsString() string {
var components []string
for k, v := range c.toMap() {
k = escapeOptionsKey(k)
component := k
if v != "" {
component = fmt.Sprintf("%s=%s", k, v)
components = append(components, component)
return strings.Join(components, ",")