GH-139416: Fix portability of sendfile(2) support detection for Lustre filesystems

Lib/shutil.py

@@ -206,10 +206,12 @@ def _fastcopy_sendfile(fsrc, fdst):
             err.filename = fsrc.name
             err.filename2 = fdst.name
 
-            if err.errno == errno.ENOTSOCK:
-                # sendfile() on this platform (probably Linux < 2.6.33)
-                # does not support copies between regular files (only
-                # sockets).
+            if err.errno in (errno.ENOTSOCK, errno.ENODATA):
+                # ENOTSOCK: sendfile() on this platform (probably
+                # Linux < 2.6.33) does not support copies between
+                # regular files (only sockets).
+                # ENODATA: In rare cases sendfile() on Linux Lustre call
+                # returns ENODATA
                 _USE_CP_SENDFILE = False
                 raise _GiveupOnFastCopy(err)
 

Misc/NEWS.d/next/Library/2025-09-29-14-30-00.gh-issue-139416.bnzz33.rst

@@ -0,0 +1,3 @@
+:func:`shutil.copyfile`: Detect problem seen on Lustre filesystems
+giving "Errno 61" due to the sendfile(2) optimised implementation and
+fall back to the Posix standard read/write implementation.