MDEV-11520 post-fix

fil_extend_space_to_desired_size(): Use a proper type cast when
computing start_offset for the posix_fallocate() call on 32-bit systems
(where sizeof(ulint) < sizeof(os_offset_t)). This could affect 32-bit
systems when extending files that are at least 4 MiB long.

This bug existed in MariaDB 10.0 before MDEV-11520. In MariaDB 10.1
it had been fixed in MDEV-11556.

storage/innobase/fil/fil0fil.cc

@@ -5016,10 +5016,12 @@ fil_extend_space_to_desired_size(
 	const ulint	file_start_page_no = space->size - node->size;
 #ifdef HAVE_POSIX_FALLOCATE
 	if (srv_use_posix_fallocate) {
-		os_offset_t	start_offset
-			= (start_page_no - file_start_page_no) * page_size;
-		ulint		n_pages = size_after_extend - start_page_no;
-		os_offset_t	len = os_offset_t(n_pages) * page_size;
+		const os_offset_t	start_offset
+			= os_offset_t(start_page_no - file_start_page_no)
+			* page_size;
+		const ulint		n_pages
+			= size_after_extend - start_page_no;
+		const os_offset_t	len = os_offset_t(n_pages) * page_size;
 
 		int err = posix_fallocate(node->handle, start_offset, len);
 		success = !err;

storage/xtradb/fil/fil0fil.cc

@@ -5056,10 +5056,12 @@ fil_extend_space_to_desired_size(
 	const ulint	file_start_page_no = space->size - node->size;
 #ifdef HAVE_POSIX_FALLOCATE
 	if (srv_use_posix_fallocate) {
-		os_offset_t	start_offset
-			= (start_page_no - file_start_page_no) * page_size;
-		ulint		n_pages = size_after_extend - start_page_no;
-		os_offset_t	len = os_offset_t(n_pages) * page_size;
+		const os_offset_t	start_offset
+			= os_offset_t(start_page_no - file_start_page_no)
+			* page_size;
+		const ulint		n_pages
+			= size_after_extend - start_page_no;
+		const os_offset_t	len = os_offset_t(n_pages) * page_size;
 
 		int err = posix_fallocate(node->handle, start_offset, len);
 		success = !err;