MDEV-18415 mariabackup.mdev-14447 test case fails with Table 'test.t' doesn't exist in engine

- Added retry logic if validation of first page fails with checksum
mismatch.

extra/mariabackup/xtrabackup.cc

@@ -3092,7 +3092,16 @@ xb_load_single_table_tablespace(
 		die("Can't open datafile %s", name);
 	}
 
-	err = file->validate_first_page(&flush_lsn);
+	for (int i = 0; i < 10; i++) {
+		err = file->validate_first_page(&flush_lsn);
+		if (err != DB_CORRUPTION) {
+			break;
+		}
+
+		my_sleep(1000);
+	}
+
+	bool is_empty_file = file->exists() && file->is_empty_file();
 
 	if (err == DB_SUCCESS && file->space_id() != SRV_TMP_SPACE_ID) {
 		os_offset_t	node_size = os_file_get_size(file->handle());
@@ -3124,9 +3133,7 @@ xb_load_single_table_tablespace(
 
 	delete file;
 
-	if (err != DB_SUCCESS && err != DB_CORRUPTION && xtrabackup_backup) {
-		/* allow corrupted first page for xtrabackup, it could be just
-		zero-filled page, which we restore from redo log later */
+	if (err != DB_SUCCESS && xtrabackup_backup && !is_empty_file) {
 		die("Failed to not validate first page of the file %s, error %d",name, (int)err);
 	}
 }

mysql-test/suite/mariabackup/mdev-14447.result

@@ -7,6 +7,7 @@ COMMIT;
 SELECT count(*) FROM t;
 count(*)
 100000
+FOUND 1 /Checksum mismatch in datafile/ in backup.log
 # Prepare full backup, apply incremental one
 # Restore and check results
 # shutdown server

mysql-test/suite/mariabackup/mdev-14447.test

@@ -1,3 +1,4 @@
+--source include/have_debug.inc
 call mtr.add_suppression("InnoDB: New log files created");
 
 let $basedir=$MYSQLTEST_VARDIR/tmp/backup;
@@ -9,16 +10,26 @@ echo # Create full backup , modify table, then create incremental/differential b
 --disable_result_log
 exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$basedir;
 --enable_result_log
+
 BEGIN;
 INSERT INTO t select uuid(), uuid(), uuid(), uuid() from seq_1_to_100000;
 COMMIT;
 SELECT count(*) FROM t;
 
-exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$incremental_dir --incremental-basedir=$basedir;
+let $backuplog=$MYSQLTEST_VARDIR/tmp/backup.log;
+
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$incremental_dir --incremental-basedir=$basedir --dbug=+d,page_intermittent_checksum_mismatch 2> $backuplog;
+
+--let SEARCH_RANGE = 10000000
+--let SEARCH_PATTERN=Checksum mismatch in datafile
+--let SEARCH_FILE=$backuplog
+--source include/search_pattern_in_file.inc
+remove_file $backuplog;
 
 --disable_result_log
 echo # Prepare full backup, apply incremental one;
 exec $XTRABACKUP --prepare --verbose --apply-log-only --target-dir=$basedir;
+
 exec $XTRABACKUP --prepare --verbose --apply-log-only --target-dir=$basedir --incremental-dir=$incremental_dir ;
 
 echo # Restore and check results;
@@ -36,7 +47,6 @@ exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --copy-back --datadir=
 echo # restart server;
 --source include/start_mysqld.inc
 
-
 --enable_result_log
 SELECT count(*) FROM t;
 DROP TABLE t;

storage/innobase/buf/buf0buf.cc

@@ -1103,6 +1103,16 @@ buf_page_is_corrupted(
 
 			if (srv_checksum_algorithm
 			    == SRV_CHECKSUM_ALGORITHM_CRC32) {
+
+				DBUG_EXECUTE_IF(
+					"page_intermittent_checksum_mismatch", {
+					static int page_counter;
+					if (page_counter++ == 2) {
+						checksum_field2++;
+					}
+				});
+
+
 				crc32 = buf_page_check_crc32(read_buf,
 							     checksum_field2);
 				crc32_inited = true;

storage/innobase/include/fsp0file.h

@@ -314,6 +314,25 @@ public:
 		return(m_last_os_error);
 	}
 
+	/** Check whether the file is empty.
+	@return true if file is empty */
+	bool	is_empty_file()		const
+	{
+#ifdef _WIN32
+		os_offset_t	offset =
+			(os_offset_t) m_file_info.nFileSizeLow
+			| ((os_offset_t) m_file_info.nFileSizeHigh << 32);
+
+		return (offset == 0);
+#else
+		return (m_file_info.st_size == 0);
+#endif
+	}
+
+	/** Check if the file exist.
+	@return true if file exists. */
+	bool exists()	const { return m_exists; }
+
 	/** Test if the filepath provided looks the same as this filepath
 	by string comparison. If they are two different paths to the same
 	file, same_as() will be used to show that after the files are opened.