You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
269 lines
9.2 KiB
Go
269 lines
9.2 KiB
Go
// 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 (
|
|
"context"
|
|
"fmt"
|
|
"log"
|
|
"runtime"
|
|
"strings"
|
|
)
|
|
|
|
// 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
|
|
|
|
// Linux only. OS X always behaves as if writeback caching is disabled.
|
|
//
|
|
// By default on Linux we allow the kernel to perform writeback caching
|
|
// (cf. http://goo.gl/LdZzo1):
|
|
//
|
|
// * When the user calls write(2), the kernel sticks the user's data into
|
|
// its page cache. Only later does it call through to the file system,
|
|
// potentially after coalescing multiple small user writes.
|
|
//
|
|
// * The file system may receive multiple write ops from the kernel
|
|
// concurrently if there is a lot of page cache data to flush.
|
|
//
|
|
// * Write performance may be significantly improved due to the user and
|
|
// the kernel not waiting for serial round trips to the file system. This
|
|
// is especially true if the user makes tiny writes.
|
|
//
|
|
// * close(2) (and anything else calling f_op->flush) causes all dirty
|
|
// pages to be written out before it proceeds to send a FlushFileOp
|
|
// (cf. https://goo.gl/TMrY6X).
|
|
//
|
|
// * Similarly, close(2) causes the kernel to send a setattr request
|
|
// filling in the mtime if any dirty pages were flushed, since the time
|
|
// at which the pages were written to the file system can't be trusted.
|
|
//
|
|
// * close(2) (and anything else calling f_op->flush) writes out all dirty
|
|
// pages, then sends a setattr request with an appropriate mtime for
|
|
// those writes if there were any, and only then proceeds to send a
|
|
// flush.
|
|
//
|
|
// Code walk:
|
|
//
|
|
// * (https://goo.gl/zTIZQ9) fuse_flush calls write_inode_now before
|
|
// calling the file system. The latter eventually calls into
|
|
// __writeback_single_inode.
|
|
//
|
|
// * (https://goo.gl/L7Z2w5) __writeback_single_inode calls
|
|
// do_writepages, which writes out any dirty pages.
|
|
//
|
|
// * (https://goo.gl/DOPgla) __writeback_single_inode later calls
|
|
// write_inode, which calls into the superblock op struct's write_inode
|
|
// member. For fuse, this is fuse_write_inode
|
|
// (cf. https://goo.gl/eDSKOX).
|
|
//
|
|
// * (https://goo.gl/PbkGA1) fuse_write_inode calls fuse_flush_times.
|
|
//
|
|
// * (https://goo.gl/ig8x9V) fuse_flush_times sends a setttr request
|
|
// for setting the inode's mtime.
|
|
//
|
|
// However, this brings along some caveats:
|
|
//
|
|
// * The file system must handle SetInodeAttributesOp or close(2) will fail,
|
|
// due to the call chain into fuse_flush_times listed above.
|
|
//
|
|
// * The kernel caches mtime and ctime regardless of whether the file
|
|
// system tells it to do so, disregarding the result of further getattr
|
|
// requests (cf. https://goo.gl/3ZZMUw, https://goo.gl/7WtQUp). It
|
|
// appears this may be true of the file size, too. Writeback caching may
|
|
// therefore not be suitable for file systems where these attributes can
|
|
// spontaneously change for reasons the kernel doesn't observe. See
|
|
// http://goo.gl/V5WQCN for more discussion.
|
|
//
|
|
// Setting DisableWritebackCaching disables this behavior. Instead the file
|
|
// system is called one or more times for each write(2), and the user's
|
|
// syscall doesn't return until the file system returns.
|
|
DisableWritebackCaching bool
|
|
|
|
// 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
|
|
|
|
// Linux only.
|
|
//
|
|
// Linux 4.20 introduced caching symlink targets in the page cache:
|
|
// https://github.com/torvalds/linux/commit/5571f1e65486be025f73fa6aa30fb03725d362a2
|
|
//
|
|
// This is not enabled by default because the old behavior masked a bug:
|
|
// file systems could return any size in the inode attributes of
|
|
// symlinks. After enabling caching, the specified size caps the symlink
|
|
// target.
|
|
EnableSymlinkCaching bool
|
|
|
|
// Linux only.
|
|
//
|
|
// Tell the kernel to treat returning -ENOSYS on OpenFile as not needing
|
|
// OpenFile calls at all (Linux >= 3.16):
|
|
EnableNoOpenSupport bool
|
|
|
|
// Linux only.
|
|
//
|
|
// Tell the kernel to treat returning -ENOSYS on OpenDir as not needing
|
|
// OpenDir calls at all (Linux >= 5.1):
|
|
EnableNoOpendirSupport bool
|
|
|
|
// OS X only.
|
|
//
|
|
// The name of the mounted volume, as displayed in the Finder. If empty, a
|
|
// default name involving the string 'osxfuse' is used.
|
|
VolumeName string
|
|
|
|
// 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
|
|
|
|
// Sets the filesystem type (third field in /etc/mtab). /etc/mtab and
|
|
// /proc/mounts will show the filesystem type as fuse.<Subtype>.
|
|
// If not set, /proc/mounts will show the filesystem type as fuse/fuseblk.
|
|
Subtype 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
|
|
}
|
|
|
|
subtype := c.Subtype
|
|
if subtype != "" {
|
|
opts["subtype"] = subtype
|
|
}
|
|
|
|
// Read only?
|
|
if c.ReadOnly {
|
|
opts["ro"] = ""
|
|
}
|
|
|
|
// Handle OS X options.
|
|
if isDarwin {
|
|
if !c.EnableVnodeCaching {
|
|
opts["novncache"] = ""
|
|
}
|
|
|
|
if c.VolumeName != "" {
|
|
// Cf. https://github.com/osxfuse/osxfuse/wiki/Mount-options#volname
|
|
opts["volname"] = c.VolumeName
|
|
}
|
|
}
|
|
|
|
// 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
|
|
}
|
|
|
|
return opts
|
|
}
|
|
|
|
func escapeOptionsKey(s string) (res string) {
|
|
res = s
|
|
res = strings.Replace(res, `\`, `\\`, -1)
|
|
res = strings.Replace(res, `,`, `\,`, -1)
|
|
return res
|
|
}
|
|
|
|
func mapToOptionsString(opts map[string]string) string {
|
|
var components []string
|
|
for k, v := range opts {
|
|
k = escapeOptionsKey(k)
|
|
|
|
component := k
|
|
if v != "" {
|
|
component = fmt.Sprintf("%s=%s", k, v)
|
|
}
|
|
|
|
components = append(components, component)
|
|
}
|
|
|
|
return strings.Join(components, ",")
|
|
}
|
|
|
|
// Create an options string suitable for passing to the mount helper.
|
|
func (c *MountConfig) toOptionsString() string {
|
|
return mapToOptionsString(c.toMap())
|
|
}
|