RF: Precompute CIFS table to minimize overhead

Only check if symlinks might be tried

Author: effigies

nipype/utils/filemanip.py

@@ -238,25 +238,45 @@ def hash_timestamp(afile):
     return md5hex
 
 
-def _on_cifs(fname):
-    """ Checks whether a PATH is on a CIFS filesystem mounted in a POSIX
-    host (i.e., has the "mount" command).
+def _generate_cifs_table():
+    """Construct a reverse-length ordered list of mount points that
+    fall under a CIFS mount.
 
-    CIFS shares are how Docker mounts Windows host directories into containers.
-    CIFS has partial support for symlinks that can break, causing misleading
-    errors, so this test is used to disable them on such systems.
+    This precomputation allows efficient checking for whether a given path
+    would be on a CIFS filesystem.
+
+    On systems without a ``mount`` command, or with no CIFS mounts, returns an
+    empty list.
     """
     exit_code, output = subprocess.getstatusoutput("mount")
     # Not POSIX
     if exit_code != 0:
-        return False
+        return []
 
     # (path, fstype) tuples, sorted by path length (longest first)
-    paths_types = sorted((line.split()[2:5:2] for line in output.splitlines()),
+    mount_info = sorted((line.split()[2:5:2] for line in output.splitlines()),
                          key=lambda x: len(x[0]),
-                         reverse=True)
+    cifs_paths = [path for path, fstype in mount_info]
+    if cifs_paths == []:
+        return []
+
+    return [mount for mount in mount_info
+            if any(mount[0].startswith(path) for path in cifs_paths)]
+
+
+_cifs_table = _generate_cifs_table()
+
+
+def on_cifs(fname):
+    """ Checks whether a PATH is on a CIFS filesystem mounted in a POSIX
+    host (i.e., has the "mount" command).
+
+    CIFS shares are how Docker mounts Windows host directories into containers.
+    CIFS has partial support for symlinks that can break, causing misleading
+    errors, so this test is used to disable them on such systems.
+    """
     # Only the first match counts
-    for fspath, fstype in paths_types:
+    for fspath, fstype in _cifs_table:
         if fname.startswith(fspath):
             return fstype == 'cifs'
     return False
@@ -314,7 +334,7 @@ def copyfile(originalfile, newfile, copy=False, create_new=False,
         hashmethod = config.get('execution', 'hash_method').lower()
 
     # Don't try creating symlinks on CIFS
-    if _on_cifs(newfile):
+    if copy is False and on_cifs(newfile):
         copy = True
 
     # Existing file