Fix Triton NFS detection crash when df wraps long device names

deepspeed/ops/transformer/inference/triton/matmul_ext.py

@@ -33,17 +33,18 @@ def is_nfs_path(path):
             break
         path = parent
 
-    # Use the 'df' command to find the file system type for the given path
+    # POSIX output keeps long device names from wrapping onto a separate line.
     try:
-        output = subprocess.check_output(['df', '-T', path], encoding='utf-8', stderr=subprocess.DEVNULL)
+        output = subprocess.check_output(['df', '-PT', path], encoding='utf-8', stderr=subprocess.DEVNULL)
     except (subprocess.CalledProcessError, FileNotFoundError):
         return False  # Command failed or 'df' not available
 
-    # Process the output of 'df -T' to check for 'nfs' in the filesystem type column
+    # Process the output of 'df -PT' to check for 'nfs' in the filesystem type column.
     lines = output.strip().split('\n')
     if len(lines) > 1:  # The first line is headers
-        fs_type = lines[1].split()[1].lower()  # File system type is the second column
-        return 'nfs' in fs_type
+        fields = lines[1].split()
+        if len(fields) > 1:
+            return 'nfs' in fields[1].lower()
     return False
 
 

tests/unit/ops/transformer/inference/test_matmul_ext.py

@@ -0,0 +1,36 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0
+
+# DeepSpeed Team
+
+import ast
+import os
+import subprocess
+from pathlib import Path
+from typing import Callable, cast
+from unittest.mock import patch
+
+MATMUL_EXT_PATH = Path(
+    __file__).resolve().parents[5] / "deepspeed" / "ops" / "transformer" / "inference" / "triton" / "matmul_ext.py"
+
+
+def load_is_nfs_path() -> Callable[[Path], bool]:
+    tree = ast.parse(MATMUL_EXT_PATH.read_text(), filename=str(MATMUL_EXT_PATH))
+    function = next(node for node in tree.body if isinstance(node, ast.FunctionDef) and node.name == "is_nfs_path")
+    module = ast.Module(body=[function], type_ignores=[])
+    namespace = {"os": os, "subprocess": subprocess}
+    exec(compile(module, str(MATMUL_EXT_PATH), "exec"), namespace)
+    return cast(Callable[[Path], bool], namespace["is_nfs_path"])
+
+
+def test_is_nfs_path_handles_wrapped_device_name(tmp_path):
+    is_nfs_path = load_is_nfs_path()
+    busybox_output = """Filesystem           Type       1K-blocks      Used Available Use% Mounted on
+/dev/dvol0123456789abcdef0
+                     ext4       2112647088   3439616 2109191088   0% /mount
+"""
+
+    with patch.object(subprocess, "check_output", return_value=busybox_output) as check_output:
+        assert not is_nfs_path(tmp_path)
+
+    check_output.assert_called_once_with(['df', '-PT', str(tmp_path)], encoding='utf-8', stderr=subprocess.DEVNULL)