.

wcfs/wcfs.go

@@ -918,6 +918,8 @@ func (f *BigFile) invalidateBlk(ctx context.Context, blk int64) (err error) {
 }
 
 // invalidateAttr invalidates file attributes in kernel cache.
+//
+// Complements invalidateBlk and is used to invalidate file size.
 func (f *BigFile) invalidateAttr() (err error) {
 	defer xerr.Contextf(&err, "%s: invalidate attr", f.path())
 	fsconn := gfsconn
@@ -950,6 +952,8 @@ func (root *Root) mkrevfile(rev zodb.Tid, fid zodb.Oid) (_ *BigFile, release fun
 	xfrev := fsconn.LookupNode(root.Inode(), frevpath)
 	if xfrev != nil {
 		// FIXME checking for "node{0}" is fragile, but currently no other way
+		// XXX the node could be still forgotten since we are not holding open on it
+		// XXX -> always os.open unconditionally? or it is ok since it is just a cache?
 		if xfrev.String() != "node{0}" {
 			return xfrev.Node().(*BigFile), func(){}, nil
 		}
@@ -969,6 +973,10 @@ func (root *Root) mkrevfile(rev zodb.Tid, fid zodb.Oid) (_ *BigFile, release fun
 
 // ----------------------------------------
 
+// XXX Move Read here
+
+// ----------------------------------------
+
 // /(head|<rev>)/at -> readAt serves read.
 func (h *Head) readAt() []byte {
 	h.zconnMu.RLock()
@@ -1039,8 +1047,6 @@ func (bfdir *BigFileDir) lookup(out *fuse.Attr, name string, fctx *fuse.Context)
 	return f, nil
 }
 
-// XXX do we need to support unlink? -> no, @<revX>/ are automatically garbage-collected.
-
 // / -> Lookup receives client request to create @<rev>/.
 func (root *Root) Lookup(out *fuse.Attr, name string, fctx *fuse.Context) (*nodefs.Inode, fuse.Status) {
 	revd, err := root.lookup(name, fctx)
@@ -1604,6 +1610,8 @@ func main() {
 		// TODO -> teach go-fuse to handle Init.MaxPages (Linux 4.20+).
 		MaxWrite:      2*1024*1024,
 
+		// XXX tune MaxReadAhead? MaxBackground?
+
 		// OS cache that we populate with bigfile data is precious;
 		// we precisely propagate ZODB invalidations into file invalidations.
 		PreciseDataCacheControl: true,