修改fd管理的层级，将其放到fs impl里面去。尚未改完，同步code

proto/lws.proto

@@ -33,6 +33,12 @@ service LwsVfs {
   rpc fchown(chown) returns (chown) {}
   rpc frelease(release) returns (release) {}
   rpc fmkdir(mkdir) returns (mkdir) {}
+  rpc frmdir(rmdir) returns (rmdir) {}
+  rpc fflush(flush) returns (flush) {}
+  rpc fopendir(opendir) returns (opendir) {}
+  rpc freleasedir(releasedir) returns (releasedir) {}
+  rpc fcreate (create) returns (create) {}
+  rpc funlink(unlink) returns (unlink) {}
 }
 
 // The request message containing the user's name.
@@ -161,3 +167,38 @@ message mkdir {
   uint32 mode = 3;
   int32 ret = 15;
 }
+
+message rmdir {
+  string path = 1;
+  int32 ret = 15;
+}
+
+message flush {
+  string path = 1;
+  file_info fi = 2;
+  int32 ret = 15;
+}
+
+message opendir{
+  string path = 1;
+  file_info fi = 2;
+  int32 ret = 15;
+}
+
+message releasedir{
+  string path = 1;
+  file_info fi = 2;
+  int32 ret = 15;
+}
+
+message create{
+  string path = 1;
+  uint32 mode = 2;
+  file_info fi = 3;
+  int32 ret = 15;
+}
+
+message unlink{
+  string path = 1;
+  int32 ret = 15;
+}