bugfix: skip empty safetensors file when inplace pin memory

Author: HubertZhang

checkpoint_engine/pin_memory.py

@@ -258,6 +258,12 @@ def _pin(t: torch.Tensor):
         # Remove the file after successfully loading. This will avoid doubling the memory usage.
         # We assume files in /dev/shm/ are temporary files. So it's safe to remove them after loading.
         os.remove(file_path)
+        if not metas:
+            # TODO: should we still return this buffer?
+            assert buffer.nbytes == 0, f"buffer nbytes {buffer.nbytes} should be 0"
+            logger.warning(f"[rank{rank}] no metas found in {file_path}, skip pin memory")
+            return MemoryBuffer(buffer=buffer, size=buffer.nbytes, metas=[], manually_pinned=False)
+
         _pin(buffer)
         logger.info(
             f"[rank{rank}] inplace pin memory for file {file_path} finished, size {buffer.nbytes / 1024 / 1024:.2f}MiB"