Add RememberInodes option to MountOptions.

fuse/api.go

@@ -251,6 +251,10 @@ type MountOptions struct {
 
 	// If given, use this buffer pool instead of the global one.
 	Buffers BufferPool
+
+	// If RememberInodes is set, we will never forget inodes.
+	// This may be useful for NFS.
+	RememberInodes bool
 }
 
 // DefaultFileSystem implements a FileSystem that returns ENOSYS for every operation.

fuse/opcode.go

@@ -211,7 +211,9 @@ func doGetAttr(state *MountState, req *request) {
 }
 
 func doForget(state *MountState, req *request) {
-	state.fileSystem.Forget(req.inHeader.NodeId, (*raw.ForgetIn)(req.inData).Nlookup)
+	if !state.opts.RememberInodes {
+		state.fileSystem.Forget(req.inHeader.NodeId, (*raw.ForgetIn)(req.inData).Nlookup)
+	}
 }
 
 func doBatchForget(state *MountState, req *request) {