From 695b70b1e63da3b0ad1f6f1afe0d23d5fe5cce29 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:39:04 +1000
Subject: [PATCH 01/14] Pasted the implementation from bazilfuse.

---
 mount_darwin.go | 131 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 mount_darwin.go

diff --git a/mount_darwin.go b/mount_darwin.go
new file mode 100644
index 0000000..cf8646f
--- /dev/null
+++ b/mount_darwin.go
@@ -0,0 +1,131 @@
+package fuseshim
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+// OS X appears to cap the size of writes to 1 MiB. This constant is also used
+// for sizing receive buffers, so make it as small as it can be without
+// limiting write sizes.
+const maxWrite = 1 << 20
+
+var errNoAvail = errors.New("no available fuse devices")
+
+var errNotLoaded = errors.New("osxfusefs is not loaded")
+
+func loadOSXFUSE() error {
+	cmd := exec.Command("/Library/Filesystems/osxfusefs.fs/Support/load_osxfusefs")
+	cmd.Dir = "/"
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err := cmd.Run()
+	return err
+}
+
+func openOSXFUSEDev() (*os.File, error) {
+	var f *os.File
+	var err error
+	for i := uint64(0); ; i++ {
+		path := "/dev/osxfuse" + strconv.FormatUint(i, 10)
+		f, err = os.OpenFile(path, os.O_RDWR, 0000)
+		if os.IsNotExist(err) {
+			if i == 0 {
+				// not even the first device was found -> fuse is not loaded
+				return nil, errNotLoaded
+			}
+
+			// we've run out of kernel-provided devices
+			return nil, errNoAvail
+		}
+
+		if err2, ok := err.(*os.PathError); ok && err2.Err == syscall.EBUSY {
+			// try the next one
+			continue
+		}
+
+		if err != nil {
+			return nil, err
+		}
+		return f, nil
+	}
+}
+
+func callMount(dir string, conf *mountConfig, f *os.File, ready chan<- struct{}, errp *error) error {
+	bin := "/Library/Filesystems/osxfusefs.fs/Support/mount_osxfusefs"
+
+	for k, v := range conf.options {
+		if strings.Contains(k, ",") || strings.Contains(v, ",") {
+			// Silly limitation but the mount helper does not
+			// understand any escaping. See TestMountOptionCommaError.
+			return fmt.Errorf("mount options cannot contain commas on darwin: %q=%q", k, v)
+		}
+	}
+	cmd := exec.Command(
+		bin,
+		"-o", conf.getOptions(),
+		// Tell osxfuse-kext how large our buffer is. It must split
+		// writes larger than this into multiple writes.
+		//
+		// OSXFUSE seems to ignore InitResponse.MaxWrite, and uses
+		// this instead.
+		"-o", "iosize="+strconv.FormatUint(maxWrite, 10),
+		// refers to fd passed in cmd.ExtraFiles
+		"3",
+		dir,
+	)
+	cmd.ExtraFiles = []*os.File{f}
+	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_CALL_BY_LIB=")
+	// TODO this is used for fs typenames etc, let app influence it
+	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_DAEMON_PATH="+bin)
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+
+	err := cmd.Start()
+	if err != nil {
+		return err
+	}
+	go func() {
+		err := cmd.Wait()
+		if err != nil {
+			if buf.Len() > 0 {
+				output := buf.Bytes()
+				output = bytes.TrimRight(output, "\n")
+				msg := err.Error() + ": " + string(output)
+				err = errors.New(msg)
+			}
+		}
+		*errp = err
+		close(ready)
+	}()
+	return err
+}
+
+func mount(dir string, conf *mountConfig, ready chan<- struct{}, errp *error) (*os.File, error) {
+	f, err := openOSXFUSEDev()
+	if err == errNotLoaded {
+		err = loadOSXFUSE()
+		if err != nil {
+			return nil, err
+		}
+		// try again
+		f, err = openOSXFUSEDev()
+	}
+	if err != nil {
+		return nil, err
+	}
+	err = callMount(dir, conf, f, ready, errp)
+	if err != nil {
+		f.Close()
+		return nil, err
+	}
+	return f, nil
+}

From 56758cb302096f1173274d39c434117622e66de1 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:45:16 +1000
Subject: [PATCH 02/14] Gave mount a makeover.

---
 mount_darwin.go | 41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/mount_darwin.go b/mount_darwin.go
index cf8646f..1f9bc55 100644
--- a/mount_darwin.go
+++ b/mount_darwin.go
@@ -1,4 +1,4 @@
-package fuseshim
+package fuse
 
 import (
 	"bytes"
@@ -109,23 +109,42 @@ func callMount(dir string, conf *mountConfig, f *os.File, ready chan<- struct{},
 	return err
 }
 
-func mount(dir string, conf *mountConfig, ready chan<- struct{}, errp *error) (*os.File, error) {
-	f, err := openOSXFUSEDev()
+// Begin the process of mounting at the given directory, returning a connection
+// to the kernel. Mounting continues in the background, and is complete when an
+// error is written to the supplied channel. The file system may need to
+// service the connection in order for mounting to complete.
+func mount(
+	dir string,
+	conf *mountConfig,
+	ready chan<- error) (dev *os.File, err error) {
+	// Open the device.
+	dev, err = openOSXFUSEDev()
+
+	// Special case: we may need to explicitly load osxfuse. Load it, then try
+	// again.
 	if err == errNotLoaded {
 		err = loadOSXFUSE()
 		if err != nil {
-			return nil, err
+			err = fmt.Errorf("loadOSXFUSE: %v", err)
+			return
 		}
-		// try again
-		f, err = openOSXFUSEDev()
+
+		dev, err = openOSXFUSEDev()
 	}
+
+	// Propagate errors.
 	if err != nil {
-		return nil, err
+		err = fmt.Errorf("openOSXFUSEDev: %v", err)
+		return
 	}
-	err = callMount(dir, conf, f, ready, errp)
+
+	// Call the mount binary with the device.
+	err = callMount(dir, conf, dev, ready)
 	if err != nil {
-		f.Close()
-		return nil, err
+		dev.Close()
+		err = fmt.Errorf("callMount: %v", err)
+		return
 	}
-	return f, nil
+
+	return
 }

From 1bb0fd472497dcc36d3e586e6450878ec2d51420 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:45:34 +1000
Subject: [PATCH 03/14] Trimmed a bit.

---
 mount_darwin.go | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/mount_darwin.go b/mount_darwin.go
index 1f9bc55..4980396 100644
--- a/mount_darwin.go
+++ b/mount_darwin.go
@@ -11,11 +11,6 @@ import (
 	"syscall"
 )
 
-// OS X appears to cap the size of writes to 1 MiB. This constant is also used
-// for sizing receive buffers, so make it as small as it can be without
-// limiting write sizes.
-const maxWrite = 1 << 20
-
 var errNoAvail = errors.New("no available fuse devices")
 
 var errNotLoaded = errors.New("osxfusefs is not loaded")

From eda994c2e66a9dc298c24b8ebdb7fad2b08f7485 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:48:17 +1000
Subject: [PATCH 04/14] Gave openOSXFUSEDev a makeover.

---
 mount_darwin.go | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/mount_darwin.go b/mount_darwin.go
index 4980396..c540228 100644
--- a/mount_darwin.go
+++ b/mount_darwin.go
@@ -24,31 +24,29 @@ func loadOSXFUSE() error {
 	return err
 }
 
-func openOSXFUSEDev() (*os.File, error) {
-	var f *os.File
-	var err error
+func openOSXFUSEDev() (dev *os.File, err error) {
+	// Try each device name.
 	for i := uint64(0); ; i++ {
-		path := "/dev/osxfuse" + strconv.FormatUint(i, 10)
-		f, err = os.OpenFile(path, os.O_RDWR, 0000)
+		path := fmt.Sprintf("/dev/osxfuse%d", i)
+		dev, err = os.OpenFile(path, os.O_RDWR, 0000)
 		if os.IsNotExist(err) {
 			if i == 0 {
-				// not even the first device was found -> fuse is not loaded
-				return nil, errNotLoaded
+				// Not even the first device was found. Fuse must not be loaded.
+				err = errNotLoaded
+				return
 			}
 
-			// we've run out of kernel-provided devices
-			return nil, errNoAvail
+			// Otherwise we've run out of kernel-provided devices
+			err = errNoAvail
+			return
 		}
 
 		if err2, ok := err.(*os.PathError); ok && err2.Err == syscall.EBUSY {
-			// try the next one
+			// This device is in use; try the next one.
 			continue
 		}
 
-		if err != nil {
-			return nil, err
-		}
-		return f, nil
+		return
 	}
 }
 

From a9693474e8b68e2bb96fc564f90f07fa2a767182 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:48:23 +1000
Subject: [PATCH 05/14] Fixed a build error.

---
 mount_darwin.go | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mount_darwin.go b/mount_darwin.go
index c540228..ababb03 100644
--- a/mount_darwin.go
+++ b/mount_darwin.go
@@ -9,10 +9,11 @@ import (
 	"strconv"
 	"strings"
 	"syscall"
+
+	"github.com/jacobsa/fuse/internal/buffer"
 )
 
 var errNoAvail = errors.New("no available fuse devices")
-
 var errNotLoaded = errors.New("osxfusefs is not loaded")
 
 func loadOSXFUSE() error {
@@ -68,7 +69,7 @@ func callMount(dir string, conf *mountConfig, f *os.File, ready chan<- struct{},
 		//
 		// OSXFUSE seems to ignore InitResponse.MaxWrite, and uses
 		// this instead.
-		"-o", "iosize="+strconv.FormatUint(maxWrite, 10),
+		"-o", "iosize="+strconv.FormatUint(buffer.MaxWriteSize, 10),
 		// refers to fd passed in cmd.ExtraFiles
 		"3",
 		dir,

From 19934c68be62c2b1d2a1addbfe3a69d2d148c67c Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:51:18 +1000
Subject: [PATCH 06/14] Touched up callMount.

---
 mount_darwin.go | 38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/mount_darwin.go b/mount_darwin.go
index ababb03..41137cd 100644
--- a/mount_darwin.go
+++ b/mount_darwin.go
@@ -51,16 +51,25 @@ func openOSXFUSEDev() (dev *os.File, err error) {
 	}
 }
 
-func callMount(dir string, conf *mountConfig, f *os.File, ready chan<- struct{}, errp *error) error {
-	bin := "/Library/Filesystems/osxfusefs.fs/Support/mount_osxfusefs"
+func callMount(
+	dir string,
+	cfg *mountConfig,
+	dev *os.File,
+	ready chan<- error) (err error) {
+	const bin = "/Library/Filesystems/osxfusefs.fs/Support/mount_osxfusefs"
 
+	// The mount helper doesn't understand any escaping.
 	for k, v := range conf.options {
 		if strings.Contains(k, ",") || strings.Contains(v, ",") {
-			// Silly limitation but the mount helper does not
-			// understand any escaping. See TestMountOptionCommaError.
-			return fmt.Errorf("mount options cannot contain commas on darwin: %q=%q", k, v)
+			return fmt.Errorf(
+				"mount options cannot contain commas on darwin: %q=%q",
+				k,
+				v)
 		}
 	}
+
+	// Call the mount helper, passing in the device file and saving output into a
+	// buffer.
 	cmd := exec.Command(
 		bin,
 		"-o", conf.getOptions(),
@@ -74,33 +83,36 @@ func callMount(dir string, conf *mountConfig, f *os.File, ready chan<- struct{},
 		"3",
 		dir,
 	)
-	cmd.ExtraFiles = []*os.File{f}
+	cmd.ExtraFiles = []*os.File{dev}
 	cmd.Env = os.Environ()
 	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_CALL_BY_LIB=")
 	// TODO this is used for fs typenames etc, let app influence it
 	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_DAEMON_PATH="+bin)
+
 	var buf bytes.Buffer
 	cmd.Stdout = &buf
 	cmd.Stderr = &buf
 
-	err := cmd.Start()
+	err = cmd.Start()
 	if err != nil {
-		return err
+		return
 	}
+
+	// In the background, wait for the command to complete.
 	go func() {
 		err := cmd.Wait()
 		if err != nil {
 			if buf.Len() > 0 {
 				output := buf.Bytes()
 				output = bytes.TrimRight(output, "\n")
-				msg := err.Error() + ": " + string(output)
-				err = errors.New(msg)
+				err = fmt.Errorf("%v: %s", err, output)
 			}
 		}
-		*errp = err
-		close(ready)
+
+		ready <- err
 	}()
-	return err
+
+	return
 }
 
 // Begin the process of mounting at the given directory, returning a connection

From cd6c68c83f573d2478b6291b7df546021df971f3 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:54:02 +1000
Subject: [PATCH 07/14] Fixed some build errors.

---
 mount_darwin.go        | 10 +++++-----
 mounted_file_system.go | 11 +++++++++++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/mount_darwin.go b/mount_darwin.go
index 41137cd..428b73a 100644
--- a/mount_darwin.go
+++ b/mount_darwin.go
@@ -53,13 +53,13 @@ func openOSXFUSEDev() (dev *os.File, err error) {
 
 func callMount(
 	dir string,
-	cfg *mountConfig,
+	cfg *MountConfig,
 	dev *os.File,
 	ready chan<- error) (err error) {
 	const bin = "/Library/Filesystems/osxfusefs.fs/Support/mount_osxfusefs"
 
 	// The mount helper doesn't understand any escaping.
-	for k, v := range conf.options {
+	for k, v := range cfg.toMap() {
 		if strings.Contains(k, ",") || strings.Contains(v, ",") {
 			return fmt.Errorf(
 				"mount options cannot contain commas on darwin: %q=%q",
@@ -72,7 +72,7 @@ func callMount(
 	// buffer.
 	cmd := exec.Command(
 		bin,
-		"-o", conf.getOptions(),
+		"-o", cfg.toOptionsString(),
 		// Tell osxfuse-kext how large our buffer is. It must split
 		// writes larger than this into multiple writes.
 		//
@@ -121,7 +121,7 @@ func callMount(
 // service the connection in order for mounting to complete.
 func mount(
 	dir string,
-	conf *mountConfig,
+	cfg *MountConfig,
 	ready chan<- error) (dev *os.File, err error) {
 	// Open the device.
 	dev, err = openOSXFUSEDev()
@@ -145,7 +145,7 @@ func mount(
 	}
 
 	// Call the mount binary with the device.
-	err = callMount(dir, conf, dev, ready)
+	err = callMount(dir, cfg, dev, ready)
 	if err != nil {
 		dev.Close()
 		err = fmt.Errorf("callMount: %v", err)
diff --git a/mounted_file_system.go b/mounted_file_system.go
index 4a57ec6..2d4ab4e 100644
--- a/mounted_file_system.go
+++ b/mounted_file_system.go
@@ -112,6 +112,17 @@ type MountConfig struct {
 	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) {
+	panic("TODO")
+}
+
+// Create an options string suitable for passing to the mount helper.
+func (c *MountConfig) toOptionsString() string {
+	panic("TODO")
+}
+
 // Convert to mount options to be passed to package fuseshim.
 func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
 	isDarwin := runtime.GOOS == "darwin"

From d2b9accc31805aed67ca858db591e4d71a3bc7a6 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:55:03 +1000
Subject: [PATCH 08/14] Moved MountConfig into a separate file.

---
 mount_config.go        | 158 +++++++++++++++++++++++++++++++++++++++++
 mounted_file_system.go | 136 -----------------------------------
 2 files changed, 158 insertions(+), 136 deletions(-)
 create mode 100644 mount_config.go

diff --git a/mount_config.go b/mount_config.go
new file mode 100644
index 0000000..8081591
--- /dev/null
+++ b/mount_config.go
@@ -0,0 +1,158 @@
+// 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,
+// 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 fuse
+
+import (
+	"log"
+	"runtime"
+
+	"github.com/jacobsa/fuse/internal/fuseshim"
+
+	"golang.org/x/net/context"
+)
+
+// 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) {
+	panic("TODO")
+}
+
+// Create an options string suitable for passing to the mount helper.
+func (c *MountConfig) toOptionsString() string {
+	panic("TODO")
+}
+
+// Convert to mount options to be passed to package fuseshim.
+func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
+	isDarwin := runtime.GOOS == "darwin"
+
+	// Enable permissions checking in the kernel. See the comments on
+	// InodeAttributes.Mode.
+	opts = append(opts, fuseshim.SetOption("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 = append(opts, fuseshim.FSName(fsname))
+	}
+
+	// Read only?
+	if c.ReadOnly {
+		opts = append(opts, fuseshim.ReadOnly())
+	}
+
+	// OS X: set novncache when appropriate.
+	if isDarwin && !c.EnableVnodeCaching {
+		opts = append(opts, fuseshim.SetOption("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 = append(opts, fuseshim.SetOption("noappledouble", ""))
+	}
+
+	// Ask the Linux kernel for larger read requests.
+	//
+	// As of 2015-03-26, the behavior in the kernel is:
+	//
+	//  *  (http://goo.gl/bQ1f1i, http://goo.gl/HwBrR6) Set the local variable
+	//     ra_pages to be init_response->max_readahead divided by the page size.
+	//
+	//  *  (http://goo.gl/gcIsSh, http://goo.gl/LKV2vA) Set
+	//     backing_dev_info::ra_pages to the min of that value and what was sent
+	//     in the request's max_readahead field.
+	//
+	//  *  (http://goo.gl/u2SqzH) Use backing_dev_info::ra_pages when deciding
+	//     how much to read ahead.
+	//
+	//  *  (http://goo.gl/JnhbdL) Don't read ahead at all if that field is zero.
+	//
+	// Reading a page at a time is a drag. Ask for a larger size.
+	const maxReadahead = 1 << 20
+	opts = append(opts, fuseshim.MaxReadahead(maxReadahead))
+
+	// Last but not least: other user-supplied options.
+	for k, v := range c.Options {
+		opts = append(opts, fuseshim.SetOption(k, v))
+	}
+
+	return
+}
diff --git a/mounted_file_system.go b/mounted_file_system.go
index 2d4ab4e..d070353 100644
--- a/mounted_file_system.go
+++ b/mounted_file_system.go
@@ -16,8 +16,6 @@ package fuse
 
 import (
 	"fmt"
-	"log"
-	"runtime"
 
 	"github.com/jacobsa/fuse/internal/fuseshim"
 
@@ -63,140 +61,6 @@ func (mfs *MountedFileSystem) Join(ctx context.Context) error {
 	}
 }
 
-// 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) {
-	panic("TODO")
-}
-
-// Create an options string suitable for passing to the mount helper.
-func (c *MountConfig) toOptionsString() string {
-	panic("TODO")
-}
-
-// Convert to mount options to be passed to package fuseshim.
-func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
-	isDarwin := runtime.GOOS == "darwin"
-
-	// Enable permissions checking in the kernel. See the comments on
-	// InodeAttributes.Mode.
-	opts = append(opts, fuseshim.SetOption("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 = append(opts, fuseshim.FSName(fsname))
-	}
-
-	// Read only?
-	if c.ReadOnly {
-		opts = append(opts, fuseshim.ReadOnly())
-	}
-
-	// OS X: set novncache when appropriate.
-	if isDarwin && !c.EnableVnodeCaching {
-		opts = append(opts, fuseshim.SetOption("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 = append(opts, fuseshim.SetOption("noappledouble", ""))
-	}
-
-	// Ask the Linux kernel for larger read requests.
-	//
-	// As of 2015-03-26, the behavior in the kernel is:
-	//
-	//  *  (http://goo.gl/bQ1f1i, http://goo.gl/HwBrR6) Set the local variable
-	//     ra_pages to be init_response->max_readahead divided by the page size.
-	//
-	//  *  (http://goo.gl/gcIsSh, http://goo.gl/LKV2vA) Set
-	//     backing_dev_info::ra_pages to the min of that value and what was sent
-	//     in the request's max_readahead field.
-	//
-	//  *  (http://goo.gl/u2SqzH) Use backing_dev_info::ra_pages when deciding
-	//     how much to read ahead.
-	//
-	//  *  (http://goo.gl/JnhbdL) Don't read ahead at all if that field is zero.
-	//
-	// Reading a page at a time is a drag. Ask for a larger size.
-	const maxReadahead = 1 << 20
-	opts = append(opts, fuseshim.MaxReadahead(maxReadahead))
-
-	// Last but not least: other user-supplied options.
-	for k, v := range c.Options {
-		opts = append(opts, fuseshim.SetOption(k, v))
-	}
-
-	return
-}
-
 // Attempt to mount a file system on the given directory, using the supplied
 // Server to serve connection requests. This function blocks until the file
 // system is successfully mounted.

From baa7c29fad8bee992d9c1bdd518e55b077523b2c Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 15:56:54 +1000
Subject: [PATCH 09/14] Use the mount helper in Mount.

---
 mounted_file_system.go | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/mounted_file_system.go b/mounted_file_system.go
index d070353..54532bb 100644
--- a/mounted_file_system.go
+++ b/mounted_file_system.go
@@ -17,8 +17,6 @@ package fuse
 import (
 	"fmt"
 
-	"github.com/jacobsa/fuse/internal/fuseshim"
-
 	"golang.org/x/net/context"
 )
 
@@ -74,10 +72,11 @@ func Mount(
 		joinStatusAvailable: make(chan struct{}),
 	}
 
-	// Open a fuseshim connection.
-	bfConn, err := fuseshim.Mount(mfs.dir, config.bazilfuseOptions()...)
+	// Begin the mounting process, which will continue in the background.
+	ready := make(chan error, 1)
+	dev, err := mount(dir, config, ready)
 	if err != nil {
-		err = fmt.Errorf("fuseshim.Mount: %v", err)
+		err = fmt.Errorf("mount: %v", err)
 		return
 	}
 
@@ -87,15 +86,14 @@ func Mount(
 		opContext = context.Background()
 	}
 
-	// Create our own Connection object wrapping it.
+	// Create a Connection object wrapping the device.
 	connection, err := newConnection(
 		opContext,
 		config.DebugLogger,
 		config.ErrorLogger,
-		bfConn)
+		dev)
 
 	if err != nil {
-		bfConn.Close()
 		err = fmt.Errorf("newConnection: %v", err)
 		return
 	}
@@ -107,9 +105,9 @@ func Mount(
 		close(mfs.joinStatusAvailable)
 	}()
 
-	// Wait for the connection to say it is ready.
-	if err = connection.waitForReady(); err != nil {
-		err = fmt.Errorf("WaitForReady: %v", err)
+	// Wait for the mount process to complete.
+	if err = <-ready; err != nil {
+		err = fmt.Errorf("mount (background): %v", err)
 		return
 	}
 

From 28605268713e6c49c9d7a0377f38307277e409bd Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 16:01:45 +1000
Subject: [PATCH 10/14] Updated newConnection.

---
 connection.go             | 18 +++++++++++++++---
 internal/fuseshim/fuse.go | 11 +++++++----
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/connection.go b/connection.go
index 4e83b8b..878f302 100644
--- a/connection.go
+++ b/connection.go
@@ -58,15 +58,27 @@ type Connection struct {
 	cancelFuncs map[uint64]func()
 }
 
-// Responsibility for closing the wrapped connection is transferred to the
-// result. You must call c.close() eventually.
+// Create a connection wrapping the supplied file descriptor connected to the
+// kernel. You must eventually call c.close().
 //
 // The loggers may be nil.
 func newConnection(
 	parentCtx context.Context,
 	debugLogger *log.Logger,
 	errorLogger *log.Logger,
-	wrapped *fuseshim.Conn) (c *Connection, err error) {
+	dev *os.File) (c *Connection, err error) {
+	// Create an initialized a wrapped fuseshim connection.
+	wrapped := &fuseshim.Conn{
+		Dev: dev,
+	}
+
+	err = fuseshim.InitMount(wrapped, TODO, TODO)
+	if err != nil {
+		err = fmt.Errorf("fuseshim.InitMount: %v", err)
+		return
+	}
+
+	// Create an object wrapping it.
 	c = &Connection{
 		debugLogger: debugLogger,
 		errorLogger: errorLogger,
diff --git a/internal/fuseshim/fuse.go b/internal/fuseshim/fuse.go
index 22fde82..8b2d3a1 100644
--- a/internal/fuseshim/fuse.go
+++ b/internal/fuseshim/fuse.go
@@ -164,7 +164,7 @@ func Mount(dir string, options ...MountOption) (*Conn, error) {
 	}
 	c.Dev = f
 
-	if err := initMount(c, &conf); err != nil {
+	if err := InitMount(c, conf.maxReadahead, conf.initFlags); err != nil {
 		c.Close()
 		return nil, err
 	}
@@ -181,7 +181,10 @@ func (e *OldVersionError) Error() string {
 	return fmt.Sprintf("kernel FUSE version is too old: %v < %v", e.Kernel, e.LibraryMin)
 }
 
-func initMount(c *Conn, conf *mountConfig) error {
+func InitMount(
+	c *Conn,
+	maxReadahead uint32,
+	initFlags fusekernel.InitFlags) error {
 	req, err := c.ReadRequest()
 	if err != nil {
 		if err == io.EOF {
@@ -213,9 +216,9 @@ func initMount(c *Conn, conf *mountConfig) error {
 
 	s := &InitResponse{
 		Library:      proto,
-		MaxReadahead: conf.maxReadahead,
+		MaxReadahead: maxReadahead,
 		MaxWrite:     maxWrite,
-		Flags:        fusekernel.InitBigWrites | conf.initFlags,
+		Flags:        fusekernel.InitBigWrites | initFlags,
 	}
 	r.Respond(s)
 	return nil

From 91664cfc31f23af5d5e1310cc74cbd67a3c2002c Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 16:03:24 +1000
Subject: [PATCH 11/14] Fixed maxReadahead.

---
 connection.go   | 21 ++++++++++++++++++++-
 mount_config.go | 20 --------------------
 2 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/connection.go b/connection.go
index 878f302..ab465bd 100644
--- a/connection.go
+++ b/connection.go
@@ -32,6 +32,25 @@ import (
 	"github.com/jacobsa/fuse/internal/fuseshim"
 )
 
+// Ask the Linux kernel for larger read requests.
+//
+// As of 2015-03-26, the behavior in the kernel is:
+//
+//  *  (http://goo.gl/bQ1f1i, http://goo.gl/HwBrR6) Set the local variable
+//     ra_pages to be init_response->max_readahead divided by the page size.
+//
+//  *  (http://goo.gl/gcIsSh, http://goo.gl/LKV2vA) Set
+//     backing_dev_info::ra_pages to the min of that value and what was sent
+//     in the request's max_readahead field.
+//
+//  *  (http://goo.gl/u2SqzH) Use backing_dev_info::ra_pages when deciding
+//     how much to read ahead.
+//
+//  *  (http://goo.gl/JnhbdL) Don't read ahead at all if that field is zero.
+//
+// Reading a page at a time is a drag. Ask for a larger size.
+const maxReadahead = 1 << 20
+
 // A connection to the fuse kernel process.
 type Connection struct {
 	debugLogger *log.Logger
@@ -72,7 +91,7 @@ func newConnection(
 		Dev: dev,
 	}
 
-	err = fuseshim.InitMount(wrapped, TODO, TODO)
+	err = fuseshim.InitMount(wrapped, maxReadahead, TODO)
 	if err != nil {
 		err = fmt.Errorf("fuseshim.InitMount: %v", err)
 		return
diff --git a/mount_config.go b/mount_config.go
index 8081591..cf1fff8 100644
--- a/mount_config.go
+++ b/mount_config.go
@@ -129,26 +129,6 @@ func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
 		opts = append(opts, fuseshim.SetOption("noappledouble", ""))
 	}
 
-	// Ask the Linux kernel for larger read requests.
-	//
-	// As of 2015-03-26, the behavior in the kernel is:
-	//
-	//  *  (http://goo.gl/bQ1f1i, http://goo.gl/HwBrR6) Set the local variable
-	//     ra_pages to be init_response->max_readahead divided by the page size.
-	//
-	//  *  (http://goo.gl/gcIsSh, http://goo.gl/LKV2vA) Set
-	//     backing_dev_info::ra_pages to the min of that value and what was sent
-	//     in the request's max_readahead field.
-	//
-	//  *  (http://goo.gl/u2SqzH) Use backing_dev_info::ra_pages when deciding
-	//     how much to read ahead.
-	//
-	//  *  (http://goo.gl/JnhbdL) Don't read ahead at all if that field is zero.
-	//
-	// Reading a page at a time is a drag. Ask for a larger size.
-	const maxReadahead = 1 << 20
-	opts = append(opts, fuseshim.MaxReadahead(maxReadahead))
-
 	// Last but not least: other user-supplied options.
 	for k, v := range c.Options {
 		opts = append(opts, fuseshim.SetOption(k, v))

From ba66e02af11d9d55a0c8fdf84fa88aeea1d93fd1 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 16:05:01 +1000
Subject: [PATCH 12/14] Fixed initFlags.

---
 connection.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/connection.go b/connection.go
index ab465bd..b136e06 100644
--- a/connection.go
+++ b/connection.go
@@ -91,7 +91,7 @@ func newConnection(
 		Dev: dev,
 	}
 
-	err = fuseshim.InitMount(wrapped, maxReadahead, TODO)
+	err = fuseshim.InitMount(wrapped, maxReadahead, 0)
 	if err != nil {
 		err = fmt.Errorf("fuseshim.InitMount: %v", err)
 		return

From 440c9ee7f7441bb1c7c27535c99f7ad0b680384c Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 16:06:53 +1000
Subject: [PATCH 13/14] MountConfig.toMap

---
 mount_config.go | 30 ++++++++++++------------------
 1 file changed, 12 insertions(+), 18 deletions(-)

diff --git a/mount_config.go b/mount_config.go
index cf1fff8..e20c915 100644
--- a/mount_config.go
+++ b/mount_config.go
@@ -18,8 +18,6 @@ import (
 	"log"
 	"runtime"
 
-	"github.com/jacobsa/fuse/internal/fuseshim"
-
 	"golang.org/x/net/context"
 )
 
@@ -75,21 +73,12 @@ type MountConfig struct {
 // 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) {
-	panic("TODO")
-}
-
-// Create an options string suitable for passing to the mount helper.
-func (c *MountConfig) toOptionsString() string {
-	panic("TODO")
-}
-
-// Convert to mount options to be passed to package fuseshim.
-func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
 	isDarwin := runtime.GOOS == "darwin"
+	opts = make(map[string]string)
 
 	// Enable permissions checking in the kernel. See the comments on
 	// InodeAttributes.Mode.
-	opts = append(opts, fuseshim.SetOption("default_permissions", ""))
+	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
@@ -107,17 +96,17 @@ func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
 
 	// Special file system name?
 	if fsname != "" {
-		opts = append(opts, fuseshim.FSName(fsname))
+		opts["fsname"] = fsname
 	}
 
 	// Read only?
 	if c.ReadOnly {
-		opts = append(opts, fuseshim.ReadOnly())
+		opts["ro"] = ""
 	}
 
 	// OS X: set novncache when appropriate.
 	if isDarwin && !c.EnableVnodeCaching {
-		opts = append(opts, fuseshim.SetOption("novncache", ""))
+		opts["novncache"] = ""
 	}
 
 	// OS X: disable the use of "Apple Double" (._foo and .DS_Store) files, which
@@ -126,13 +115,18 @@ func (c *MountConfig) bazilfuseOptions() (opts []fuseshim.MountOption) {
 	//
 	// Cf. https://github.com/osxfuse/osxfuse/wiki/Mount-options
 	if isDarwin {
-		opts = append(opts, fuseshim.SetOption("noappledouble", ""))
+		opts["noappledouble"] = ""
 	}
 
 	// Last but not least: other user-supplied options.
 	for k, v := range c.Options {
-		opts = append(opts, fuseshim.SetOption(k, v))
+		opts[k] = v
 	}
 
 	return
 }
+
+// Create an options string suitable for passing to the mount helper.
+func (c *MountConfig) toOptionsString() string {
+	panic("TODO")
+}

From f4d8f9816579c857d0fb97295c476e391dde8560 Mon Sep 17 00:00:00 2001
From: Aaron Jacobs <jacobsa@google.com>
Date: Fri, 24 Jul 2015 16:09:15 +1000
Subject: [PATCH 14/14] MountConfig.toOptionsString

---
 mount_config.go | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/mount_config.go b/mount_config.go
index e20c915..dd76561 100644
--- a/mount_config.go
+++ b/mount_config.go
@@ -15,8 +15,10 @@
 package fuse
 
 import (
+	"fmt"
 	"log"
 	"runtime"
+	"strings"
 
 	"golang.org/x/net/context"
 )
@@ -126,7 +128,26 @@ func (c *MountConfig) toMap() (opts map[string]string) {
 	return
 }
 
+func escapeOptionsKey(s string) (res string) {
+	res = s
+	res = strings.Replace(res, `\`, `\\`, -1)
+	res = strings.Replace(res, `,`, `\,`, -1)
+	return
+}
+
 // Create an options string suitable for passing to the mount helper.
 func (c *MountConfig) toOptionsString() string {
-	panic("TODO")
+	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, ",")
 }