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// Copyright 2020 the Go-FUSE Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fs_test
import (
"context"
"fmt"
"log"
"sync"
"syscall"
"time"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
)
// WindowsNode emulates Windows FS semantics, which forbids deleting open files.
type WindowsNode struct {
// WindowsNode inherits most functionality from LoopbackNode.
fs.LoopbackNode
mu sync.Mutex
openCount int
}
var _ = (fs.NodeOpener)((*WindowsNode)(nil))
func (n *WindowsNode) Open(ctx context.Context, flags uint32) (fs.FileHandle, uint32, syscall.Errno) {
fh, flags, errno := n.LoopbackNode.Open(ctx, flags)
if errno == 0 {
n.mu.Lock()
defer n.mu.Unlock()
n.openCount++
}
return fh, flags, errno
}
var _ = (fs.NodeCreater)((*WindowsNode)(nil))
func (n *WindowsNode) Create(ctx context.Context, name string, flags uint32, mode uint32, out *fuse.EntryOut) (*fs.Inode, fs.FileHandle, uint32, syscall.Errno) {
inode, fh, flags, errno := n.LoopbackNode.Create(ctx, name, flags, mode, out)
if errno == 0 {
wn := inode.Operations().(*WindowsNode)
wn.openCount++
}
return inode, fh, flags, errno
}
var _ = (fs.NodeReleaser)((*WindowsNode)(nil))
// Release decreases the open count. The kernel doesn't wait with
// returning from close(), so if the caller is too quick to
// unlink/rename after calling close(), this may still trigger EBUSY.
func (n *WindowsNode) Release(ctx context.Context, f fs.FileHandle) syscall.Errno {
n.mu.Lock()
defer n.mu.Unlock()
n.openCount--
if fr, ok := f.(fs.FileReleaser); ok {
return fr.Release(ctx)
}
return 0
}
func isBusy(parent *fs.Inode, name string) bool {
if ch := parent.GetChild(name); ch != nil {
if wn, ok := ch.Operations().(*WindowsNode); ok {
wn.mu.Lock()
defer wn.mu.Unlock()
if wn.openCount > 0 {
return true
}
}
}
return false
}
var _ = (fs.NodeUnlinker)((*WindowsNode)(nil))
func (n *WindowsNode) Unlink(ctx context.Context, name string) syscall.Errno {
if isBusy(n.EmbeddedInode(), name) {
return syscall.EBUSY
}
return n.LoopbackNode.Unlink(ctx, name)
}
func newWindowsNode(rootData *fs.LoopbackRoot, parent *fs.Inode, name string, st *syscall.Stat_t) fs.InodeEmbedder {
n := &WindowsNode{
LoopbackNode: fs.LoopbackNode{
RootData: rootData,
},
}
return n
}
// ExampleLoopbackReuse shows how to build a file system on top of the
// loopback file system.
func Example_loopbackReuse() {
mntDir := "/tmp/mnt"
origDir := "/tmp/orig"
rootData := &fs.LoopbackRoot{
NewNode: newWindowsNode,
Path: origDir,
}
sec := time.Second
opts := &fs.Options{
AttrTimeout: &sec,
EntryTimeout: &sec,
}
server, err := fs.Mount(mntDir, newWindowsNode(rootData, nil, "", nil), opts)
if err != nil {
log.Fatalf("Mount fail: %v\n", err)
}
fmt.Printf("files under %s cannot be deleted if they are opened", mntDir)
server.Wait()
}
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