fuse/nodefs: return OK for OOB readdir(plus)

This apparently happens in NFS mounts of FUSE file systems when
combined with lots of FS activity. Maybe some part of the client is
caching readdir results in the wrong way?

In any event, returning OK (signifying EOF on the dirstream) is
harmless.

Change-Id: Ib09d77eae0f1af8bce46b07f386fdda20b2ccb95

fuse/nodefs/dir.go

@@ -40,8 +40,12 @@ func (d *connectorDir) ReadDir(cancel <-chan struct{}, input *fuse.ReadIn, out *
 	}
 
 	if input.Offset > uint64(len(d.stream)) {
-		// This shouldn't happen, but let's not crash.
-		return fuse.EINVAL
+		// See https://github.com/hanwen/go-fuse/issues/297
+		// This can happen for FUSE exported over NFS.  This
+		// seems incorrect, (maybe the kernel is using offsets
+		// from other opendir/readdir calls), it is harmless to reinforce that
+		// we have reached EOF.
+		return fuse.OK
 	}
 
 	todo := d.stream[input.Offset:]
@@ -75,8 +79,8 @@ func (d *connectorDir) ReadDirPlus(cancel <-chan struct{}, input *fuse.ReadIn, o
 	}
 
 	if input.Offset > uint64(len(d.stream)) {
-		// This shouldn't happen, but let's not crash.
-		return fuse.EINVAL
+		// See comment in Readdir
+		return fuse.OK
 	}
 	todo := d.stream[input.Offset:]
 	for _, e := range todo {