.

wcfs/wcfs.go

@@ -482,6 +482,8 @@ type BigFileDir struct {
 
 	// visited BTree nodes of all BigFiles
 	// -> which file + ordering for toposort on δbtree
+	//
+	// (used only for head/, not revX/)
 	indexMu     sync.Mutex
 	indexLooked *δbtree.PathSet	// XXX naming
 }
@@ -921,7 +923,7 @@ func (root *Root) mkrevfile(rev zodb.Tid, fid zodb.Oid) (_ *BigFile, err error)
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer f.Close()	// XXX -> return to caller to release when inode no longer needed
 
 	xfrev = fsconn.LookupNode(root.Inode(), frevpath)
 	// must be !nil as open succeeded	XXX better recheck
@@ -1064,10 +1066,10 @@ func (root *Root) lookup(name string, fctx *fuse.Context) (_ *Head, err error) {
 	}
 
 	bfdir := &BigFileDir{
-		Node:    newDefaultNode(),
-		head:    revDir,
-		fileTab: make(map[zodb.Oid]*BigFile),
-		// indexLooked = nil  for @revX/
+		Node:        newDefaultNode(),
+		head:        revDir,
+		fileTab:     make(map[zodb.Oid]*BigFile),
+		indexLooked: nil, // δbtree index not needed/used for @revX/
 	}
 	revDir.bfdir = bfdir
 
@@ -1141,9 +1143,12 @@ func (head *Head) bigopen(ctx context.Context, oid zodb.Oid) (_ *BigFile, err er
 		loading: make(map[int64]*blkLoadState),
 	}
 
-	head.bfdir.indexMu.Lock()	// XXX locking ok?
-	head.bfdir.indexLooked.Add(f, treePath)
-	head.bfdir.indexMu.Unlock()
+	// only head/ needs δbtree index.
+	if head.rev == 0 {
+		head.bfdir.indexMu.Lock()	// XXX locking ok?
+		head.bfdir.indexLooked.Add(f, treePath)
+		head.bfdir.indexMu.Unlock()
+	}
 
 	return f, nil
 }
@@ -1292,10 +1297,13 @@ func (f *BigFile) readBlk(ctx context.Context, blk int64, dest []byte) error {
 	loading.err = err
 	close(loading.ready)
 
-	bfdir := f.head.bfdir
-	bfdir.indexMu.Lock()		// XXX locking correct?
-	bfdir.indexLooked.Add(f, treepath)	// XXX needed only for head/
-	bfdir.indexMu.Unlock()
+	// only head/ has δbtree index.
+	if f.head.rev == 0 {
+		bfdir := f.head.bfdir
+		bfdir.indexMu.Lock()		// XXX locking correct?
+		bfdir.indexLooked.Add(f, treepath)
+		bfdir.indexMu.Unlock()
+	}
 
 	// XXX before loading.ready?
 	blkrevmax, _ := f.δFtail.LastRevOf(blk, zbf.PJar().At())