Pull comment on seekability ahead of dstpos lseek

Author: Bojan Nikolic

Lib/shutil.py

@@ -218,14 +218,15 @@ def _fastcopy_sendfile(fsrc, fdst):
                 # ENODATA.
                 _USE_CP_SENDFILE = False
 
+                # 'infd' and 'outfd' are assumed to be seekable, as
+                # they are checked to be "regular" files.
                 dstpos = os.lseek(outfd, 0, os.SEEK_CUR)
                 if dstpos > 0:
                     # Some data has already been written but we use
                     # sendfile in a mode that does not update the
                     # input fd position when reading. Hence seek the
                     # input fd to the correct position before falling
-                    # back on POSIX read/write method. Since sendfile
-                    # requires mmapable infd, it should also be seekable
+                    # back on POSIX read/write method. 
                     os.lseek(infd, dstpos, os.SEEK_SET)
 
                 raise _GiveupOnFastCopy(err)