Implement node generations.

* Use timestamp as base generation number

* increment for each newly used inode.

This prevents clashes when exporting Go-FUSE filesystems to NFS.

fuse/fsconnector.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"path/filepath"
 	"strings"
+	"sync/atomic"
 	"time"
 	"unsafe"
 
@@ -42,6 +43,9 @@ type FileSystemConnector struct {
 
 	// The root of the FUSE file system.
 	rootNode *Inode
+
+	// Used as the generation inodes.
+	generation uint64
 }
 
 func NewFileSystemOptions() *FileSystemOptions {
@@ -61,15 +65,23 @@ func NewFileSystemConnector(nodeFs NodeFileSystem, opts *FileSystemOptions) (c *
 	c.inodeMap = NewHandleMap(opts.PortableInodes)
 	c.rootNode = newInode(true, nodeFs.Root())
 
+	// Make sure we don't reuse generation numbers.
+	c.generation = uint64(time.Now().UnixNano())
+
 	c.verify()
 	c.MountRoot(nodeFs, opts)
 
 	// FUSE does not issue a LOOKUP for 1 (obviously), but it does
 	// issue a forget.  This lookupUpdate is to make the counts match.
 	c.lookupUpdate(c.rootNode)
+	
 	return c
 }
 
+func (c *FileSystemConnector) nextGeneration() uint64 {
+	return atomic.AddUint64(&c.generation, 1)
+}
+
 func (c *FileSystemConnector) verify() {
 	if !paranoia {
 		return

fuse/fsops.go

@@ -75,7 +75,7 @@ func (c *FileSystemConnector) Lookup(out *raw.EntryOut, header *raw.InHeader, na
 
 	child.mount.fillEntry(out)
 	out.NodeId = c.lookupUpdate(child)
-	out.Generation = 1
+	out.Generation = child.generation
 	out.Ino = out.NodeId
 
 	return OK

fuse/inode.go

@@ -13,6 +13,10 @@ var _ = log.Println
 type Inode struct {
 	handled Handled
 
+	// Generation number of the inode. Each (re)use of an inode
+	// should have a unique generation number.
+	generation     uint64
+	
 	// Number of open files and its protection.
 	openFilesMutex sync.Mutex
 	openFiles      []*openedFile
@@ -136,6 +140,7 @@ func (n *Inode) New(isDir bool, fsi FsNode) *Inode {
 	ch := newInode(isDir, fsi)
 	ch.mount = n.mount
 	ch.treeLock = n.treeLock
+	n.generation = ch.mount.connector.nextGeneration()
 	return ch
 }