139 lines
4.2 KiB
Go
139 lines
4.2 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fuse
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import (
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"fmt"
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"runtime"
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"github.com/jacobsa/bazilfuse"
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"golang.org/x/net/context"
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)
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// A type that knows how to serve ops read from a connection.
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type Server interface {
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// Read and serve ops from the supplied connection until EOF.
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ServeOps(*Connection)
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}
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// A struct representing the status of a mount operation, with a method that
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// waits for unmounting.
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type MountedFileSystem struct {
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dir string
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// The result to return from Join. Not valid until the channel is closed.
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joinStatus error
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joinStatusAvailable chan struct{}
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}
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// Return the directory on which the file system is mounted (or where we
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// attempted to mount it.)
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func (mfs *MountedFileSystem) Dir() string {
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return mfs.dir
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}
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// Block until a mounted file system has been unmounted. The return value will
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// be non-nil if anything unexpected happened while serving. May be called
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// multiple times.
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func (mfs *MountedFileSystem) Join(ctx context.Context) error {
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select {
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case <-mfs.joinStatusAvailable:
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return mfs.joinStatus
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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// Optional configuration accepted by Mount.
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type MountConfig struct {
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// OS X only.
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//
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// Normally on OS X we mount with the novncache option
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// (cf. http://goo.gl/1pTjuk), which disables entry caching in the kernel.
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// This is because osxfuse does not honor the entry expiration values we
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// return to it, instead caching potentially forever (cf.
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// http://goo.gl/8yR0Ie), and it is probably better to fail to cache than to
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// cache for too long, since the latter is more likely to hide consistency
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// bugs that are difficult to detect and diagnose.
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//
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// This field disables the use of novncache, restoring entry caching. Beware:
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// the value of ChildInodeEntry.EntryExpiration is ignored by the kernel, and
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// entries will be cached for an arbitrarily long time.
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EnableVnodeCaching bool
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}
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// Convert to mount options to be passed to package bazilfuse.
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func (c *MountConfig) bazilfuseOptions() (opts []bazilfuse.MountOption) {
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// Enable permissions checking in the kernel. See the comments on
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// InodeAttributes.Mode.
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opts = append(opts, bazilfuse.SetOption("default_permissions", ""))
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// OS X only: set novncache when appropriate.
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if runtime.GOOS == "darwin" && !c.EnableVnodeCaching {
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opts = append(opts, bazilfuse.SetOption("novncache", ""))
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}
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return
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}
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// Attempt to mount a file system on the given directory, using the supplied
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// Server to serve connection requests. This function blocks until the file
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// system is successfully mounted. On some systems, this requires the supplied
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// Server to make forward progress (in particular, to respond to
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// fuseops.InitOp).
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func Mount(
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dir string,
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server Server,
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config *MountConfig) (mfs *MountedFileSystem, err error) {
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logger := getLogger()
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// Initialize the struct.
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mfs = &MountedFileSystem{
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dir: dir,
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joinStatusAvailable: make(chan struct{}),
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}
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// Open a bazilfuse connection.
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logger.Println("Opening a bazilfuse connection.")
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bfConn, err := bazilfuse.Mount(mfs.dir, config.bazilfuseOptions()...)
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if err != nil {
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err = fmt.Errorf("bazilfuse.Mount: %v", err)
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return
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}
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// Create our own Connection object wrapping it.
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connection, err := newConnection(logger, bfConn)
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if err != nil {
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bfConn.Close()
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err = fmt.Errorf("newConnection: %v", err)
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return
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}
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// Serve the connection in the background. When done, set the join status.
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go func() {
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server.ServeOps(connection)
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mfs.joinStatus = connection.close()
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close(mfs.joinStatusAvailable)
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}()
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// Wait for the connection to say it is ready.
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if err = connection.waitForReady(); err != nil {
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err = fmt.Errorf("WaitForReady: %v", err)
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return
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}
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return
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}
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