Refactor __wasi_fd_sync implementation

- Always call stream.stream_ops.fsync when its available.
- Only use `Asyncify.handleSleep` when needed.

Author: sbc100

src/lib/libwasi.js

@@ -540,34 +540,27 @@ var WasiLibrary = {
     return 0;
   },
 
+  fd_sync__async: true,
   fd_sync: (fd) => {
 #if SYSCALLS_REQUIRE_FILESYSTEM
     var stream = SYSCALLS.getStreamFromFD(fd);
+    var rtn = stream.stream_ops.fsync?.(stream);
 #if ASYNCIFY
-    return Asyncify.handleSleep((wakeUp) => {
-      var mount = stream.node.mount;
-      if (!mount.type.syncfs) {
-        // We write directly to the file system, so there's nothing to do here.
-        wakeUp(0);
-        return;
+    var mount = stream.node.mount;
+    if (mount.type.syncfs) {
+      return Asyncify.handleSleep((wakeUp) => {
+        mount.type.syncfs(mount, false, (err) => wakeUp(err ? {{{ cDefs.EIO }}} : 0));
       }
-      mount.type.syncfs(mount, false, (err) => {
-        wakeUp(err ? {{{ cDefs.EIO }}} : 0);
-      });
-    });
-#else
-    if (stream.stream_ops?.fsync) {
-      return stream.stream_ops.fsync(stream);
     }
-    return 0; // we can't do anything synchronously; the in-memory FS is already synced to
+#endif
+    return rtn;
 #endif // ASYNCIFY
 #elif ASSERTIONS
     abort('fd_sync called without SYSCALLS_REQUIRE_FILESYSTEM');
 #else
     return {{{ cDefs.ENOSYS }}};
 #endif // SYSCALLS_REQUIRE_FILESYSTEM
   },
-  fd_sync__async: true,
 
   // random.h
 

test/codesize/test_codesize_hello_dylink_all.json

@@ -1,7 +1,7 @@
 {
-  "a.out.js": 245482,
+  "a.out.js": 245471,
   "a.out.nodebug.wasm": 573657,
-  "total": 819139,
+  "total": 819128,
   "sent": [
     "IMG_Init",
     "IMG_Load",