MDEV-5355: InnoDB assertion at shutdown if posix_fallocate is used in...

MDEV-5355: InnoDB assertion at shutdown if posix_fallocate is used in ut_a(node->n_pending == 0 || node->space->stop_new_ops); 

Analysis: When filespace is extended there is first prepare for IO. But if
posix_fallocate is used there was no complete IO causing assertion
at shutdown indicating that all IO is not finished.

Fix: If posix_fallocate is used to extend the filespace, there
is no need to wait for IO to complete, thus we treat this
operation as a read operation. We need to mark IO as
completed or there would be assertion on shutdown at
fil_node_close_file() because all pending IO is not finished.

storage/xtradb/fil/fil0fil.c

@@ -5027,10 +5027,16 @@ fil_extend_space_to_desired_size(
 
 	mem_free(buf2);
 
-	fil_node_complete_io(node, fil_system, OS_FILE_WRITE);
-
 #ifdef HAVE_POSIX_FALLOCATE
 complete_io:
+	/* If posix_fallocate was used to extent the file space
+	we need to complete the io. Because no actual writes were
+	dispatched read operation is enough here. Without this
+	there will be assertion at shutdown indicating that
+	all IO is not completed. */
+	fil_node_complete_io(node, fil_system, OS_FILE_READ);
+#else
+	fil_node_complete_io(node, fil_system, OS_FILE_WRITE);
 #endif
 
 	*actual_size = space->size;