nodefs: delay directory read till ReadDir

We used to read the directory already on OpenDir, which means that
we missed changes in the directory between a user's open() and
readdir() call.

https://github.com/hanwen/go-fuse/issues/252

fuse/direntry.go

@@ -53,13 +53,13 @@ func NewDirEntryList(data []byte, off uint64) *DirEntryList {
 
 // AddDirEntry tries to add an entry, and reports whether it
 // succeeded.
-func (l *DirEntryList) AddDirEntry(e DirEntry) (bool, uint64) {
+func (l *DirEntryList) AddDirEntry(e DirEntry) bool {
 	return l.Add(0, e.Name, e.Ino, e.Mode)
 }
 
 // Add adds a direntry to the DirEntryList, returning whether it
 // succeeded.
-func (l *DirEntryList) Add(prefix int, name string, inode uint64, mode uint32) (bool, uint64) {
+func (l *DirEntryList) Add(prefix int, name string, inode uint64, mode uint32) bool {
 	if inode == 0 {
 		inode = FUSE_UNKNOWN_INO
 	}
@@ -69,7 +69,7 @@ func (l *DirEntryList) Add(prefix int, name string, inode uint64, mode uint32) (
 	newLen := delta + oldLen
 
 	if newLen > l.size {
-		return false, l.offset
+		return false
 	}
 	l.buf = l.buf[:newLen]
 	oldLen += prefix
@@ -87,20 +87,20 @@ func (l *DirEntryList) Add(prefix int, name string, inode uint64, mode uint32) (
 	}
 
 	l.offset = dirent.Off
-	return true, l.offset
+	return true
 }
 
 // AddDirLookupEntry is used for ReadDirPlus. It serializes a DirEntry
 // and returns the space for entry. If no space is left, returns a nil
 // pointer.
-func (l *DirEntryList) AddDirLookupEntry(e DirEntry) (*EntryOut, uint64) {
+func (l *DirEntryList) AddDirLookupEntry(e DirEntry) *EntryOut {
 	lastStart := len(l.buf)
-	ok, off := l.Add(int(unsafe.Sizeof(EntryOut{})), e.Name,
+	ok := l.Add(int(unsafe.Sizeof(EntryOut{})), e.Name,
 		e.Ino, e.Mode)
 	if !ok {
-		return nil, off
+		return nil
 	}
-	return (*EntryOut)(unsafe.Pointer(&l.buf[lastStart])), off
+	return (*EntryOut)(unsafe.Pointer(&l.buf[lastStart]))
 }
 
 func (l *DirEntryList) bytes() []byte {

fuse/nodefs/dir.go

@@ -13,33 +13,30 @@ import (
 
 type connectorDir struct {
 	node  Node
+	inode *Inode
 	rawFS fuse.RawFileSystem
 
 	// Protect stream and lastOffset.  These are written in case
 	// there is a seek on the directory.
 	mu     sync.Mutex
 	stream []fuse.DirEntry
-
-	// lastOffset stores the last offset for a readdir. This lets
-	// readdir pick up changes to the directory made after opening
-	// it.
-	lastOffset uint64
 }
 
 func (d *connectorDir) ReadDir(input *fuse.ReadIn, out *fuse.DirEntryList) (code fuse.Status) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	if d.stream == nil {
-		return fuse.OK
-	}
 	// rewinddir() should be as if reopening directory.
 	// TODO - test this.
-	if d.lastOffset > 0 && input.Offset == 0 {
+	if d.stream == nil || input.Offset == 0 {
 		d.stream, code = d.node.OpenDir(&input.Context)
 		if !code.Ok() {
 			return code
 		}
+		d.stream = append(d.stream, d.inode.getMountDirEntries()...)
+		d.stream = append(d.stream,
+			fuse.DirEntry{Mode: fuse.S_IFDIR, Name: "."},
+			fuse.DirEntry{Mode: fuse.S_IFDIR, Name: ".."})
 	}
 
 	if input.Offset > uint64(len(d.stream)) {
@@ -53,8 +50,7 @@ func (d *connectorDir) ReadDir(input *fuse.ReadIn, out *fuse.DirEntryList) (code
 			log.Printf("got empty directory entry, mode %o.", e.Mode)
 			continue
 		}
-		ok, off := out.AddDirEntry(e)
-		d.lastOffset = off
+		ok := out.AddDirEntry(e)
 		if !ok {
 			break
 		}
@@ -66,16 +62,16 @@ func (d *connectorDir) ReadDirPlus(input *fuse.ReadIn, out *fuse.DirEntryList) (
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	if d.stream == nil {
-		return fuse.OK
-	}
-
 	// rewinddir() should be as if reopening directory.
-	if d.lastOffset > 0 && input.Offset == 0 {
+	if d.stream == nil || input.Offset == 0 {
 		d.stream, code = d.node.OpenDir(&input.Context)
 		if !code.Ok() {
 			return code
 		}
+		d.stream = append(d.stream, d.inode.getMountDirEntries()...)
+		d.stream = append(d.stream,
+			fuse.DirEntry{Mode: fuse.S_IFDIR, Name: "."},
+			fuse.DirEntry{Mode: fuse.S_IFDIR, Name: ".."})
 	}
 
 	if input.Offset > uint64(len(d.stream)) {
@@ -91,7 +87,7 @@ func (d *connectorDir) ReadDirPlus(input *fuse.ReadIn, out *fuse.DirEntryList) (
 
 		// we have to be sure entry will fit if we try to add
 		// it, or we'll mess up the lookup counts.
-		entryDest, off := out.AddDirLookupEntry(e)
+		entryDest := out.AddDirLookupEntry(e)
 		if entryDest == nil {
 			break
 		}
@@ -106,10 +102,8 @@ func (d *connectorDir) ReadDirPlus(input *fuse.ReadIn, out *fuse.DirEntryList) (
 		*entryDest = fuse.EntryOut{}
 
 		d.rawFS.Lookup(&input.InHeader, e.Name, entryDest)
-		d.lastOffset = off
 	}
 	return fuse.OK
-
 }
 
 type rawDir interface {

fuse/nodefs/fsops.go

@@ -161,16 +161,9 @@ func (c *rawBridge) GetAttr(input *fuse.GetAttrIn, out *fuse.AttrOut) (code fuse
 
 func (c *rawBridge) OpenDir(input *fuse.OpenIn, out *fuse.OpenOut) (code fuse.Status) {
 	node := c.toInode(input.NodeId)
-	stream, err := node.fsInode.OpenDir(&input.Context)
-	if err != fuse.OK {
-		return err
-	}
-	stream = append(stream, node.getMountDirEntries()...)
 	de := &connectorDir{
+		inode: node,
 		node:  node.Node(),
-		stream: append(stream,
-			fuse.DirEntry{Mode: fuse.S_IFDIR, Name: "."},
-			fuse.DirEntry{Mode: fuse.S_IFDIR, Name: ".."}),
 		rawFS: c,
 	}
 	h, opened := node.mount.registerFileHandle(node, de, nil, input.Flags)