9p: fix stat Length=0 for session files breaking 9pfuse reads

server/server.go

@@ -1238,9 +1238,13 @@ func (s *Server) makeStat(path string) plan9.Dir {
 				dir.Length = uint64(info.Size())
 			}
 		case strings.HasPrefix(path, fs.PathSessions):
-			// Skip all session file size computation during stat/readdir.
-			// Sizes are dynamic and some trigger expensive API calls.
-			// Clients read the file to discover actual size.
+			// HACK: 9pfuse trusts stat Length — if we report 0, the kernel
+			// never issues a read. Compute size by reading the file content.
+			if entry, err := s.openEntry(path); err == nil {
+				if data, err := entry.Read(); err == nil {
+					dir.Length = uint64(len(data))
+				}
+			}
 		}
 	}