MDEV-24026: InnoDB: Failing assertion: os_total_large_mem_allocated >= size upon incremental backup

mariabackup deallocated uninitialized
write_filt_ctxt.u.wf_incremental_ctxt in xtrabackup_copy_datafile() when
some table should be skipped due to parsed DDL redo log record.

extra/mariabackup/backup_copy.cc

@@ -1448,7 +1448,7 @@ out:
 
 void backup_fix_ddl(void);
 
-static lsn_t get_current_lsn(MYSQL *connection)
+lsn_t get_current_lsn(MYSQL *connection)
 {
 	static const char lsn_prefix[] = "\nLog sequence number ";
 	lsn_t lsn = 0;

extra/mariabackup/backup_copy.h

@@ -3,6 +3,7 @@
 #define XTRABACKUP_BACKUP_COPY_H
 
 #include <my_global.h>
+#include <mysql.h>
 #include "datasink.h"
 
 /* special files */
@@ -48,4 +49,7 @@ is_path_separator(char);
 bool
 directory_exists(const char *dir, bool create);
 
+lsn_t
+get_current_lsn(MYSQL *connection);
+
 #endif

extra/mariabackup/xtrabackup.cc

@@ -2578,6 +2578,8 @@ static my_bool xtrabackup_copy_datafile(fil_node_t *node, uint thread_n,
 		return(FALSE);
 	}
 
+	memset(&write_filt_ctxt, 0, sizeof(xb_write_filt_ctxt_t));
+
 	bool was_dropped;
 	pthread_mutex_lock(&backup_mutex);
 	was_dropped = (ddl_tracker.drops.find(node->space->id) != ddl_tracker.drops.end());
@@ -2605,7 +2607,6 @@ static my_bool xtrabackup_copy_datafile(fil_node_t *node, uint thread_n,
 		sizeof dst_name - 1);
 	dst_name[sizeof dst_name - 1] = '\0';
 
-	memset(&write_filt_ctxt, 0, sizeof(xb_write_filt_ctxt_t));
 	ut_a(write_filter.process != NULL);
 
 	if (write_filter.init != NULL &&
@@ -2947,8 +2948,14 @@ static void dbug_mariabackup_event(const char *event,const char *key)
 
 }
 #define DBUG_MARIABACKUP_EVENT(A, B) DBUG_EXECUTE_IF("mariabackup_events", dbug_mariabackup_event(A,B););
+#define DBUG_MB_INJECT_CODE(EVENT, KEY, CODE) \
+	DBUG_EXECUTE_IF("mariabackup_inject_code", {\
+		char *env = getenv(EVENT); \
+		if (env && !strcmp(env, KEY)) { CODE } \
+	})
 #else
 #define DBUG_MARIABACKUP_EVENT(A,B)
+#define DBUG_MB_INJECT_CODE(EVENT, KEY, CODE)
 #endif
 
 /**************************************************************************
@@ -2973,6 +2980,8 @@ data_copy_thread_func(
 
 	while ((node = datafiles_iter_next(ctxt->it)) != NULL) {
 		DBUG_MARIABACKUP_EVENT("before_copy", node->space->name);
+		DBUG_MB_INJECT_CODE("wait_innodb_redo_before_copy", node->space->name,
+			backup_wait_for_lsn(get_current_lsn(mysql_connection)););
 		/* copy the datafile */
 		if (xtrabackup_copy_datafile(node, num, NULL,
 			xtrabackup_incremental ? wf_incremental : wf_write_through))

mysql-test/suite/mariabackup/incremental_ddl_during_backup.result

@@ -2,6 +2,7 @@ call mtr.add_suppression("InnoDB: New log files created");
 CREATE TABLE t1(i INT PRIMARY KEY) ENGINE INNODB;
 CREATE TABLE t2(i INT PRIMARY KEY) ENGINE INNODB;
 CREATE TABLE t3(i INT) ENGINE INNODB;
+CREATE TABLE t10(i INT PRIMARY KEY) ENGINE INNODB;
 # Create full backup , modify table, then create incremental/differential backup
 INSERT into t1 values(1);
 # Prepare full backup, apply incremental one

mysql-test/suite/mariabackup/incremental_ddl_during_backup.test

@@ -8,6 +8,7 @@ let $incremental_dir=$MYSQLTEST_VARDIR/tmp/backup_inc1;
 CREATE TABLE t1(i INT PRIMARY KEY) ENGINE INNODB;
 CREATE TABLE t2(i INT PRIMARY KEY) ENGINE INNODB;
 CREATE TABLE t3(i INT) ENGINE INNODB;
+CREATE TABLE t10(i INT PRIMARY KEY) ENGINE INNODB;
 
 echo # Create full backup , modify table, then create incremental/differential backup;
 --disable_result_log
@@ -20,8 +21,11 @@ INSERT into t1 values(1);
 --let after_copy_test_t1=RENAME TABLE  test.t1 TO test.t1_renamed
 --let after_copy_test_t2=DROP TABLE test.t2
 --let after_copy_test_t3=CREATE INDEX a_i ON test.t3(i);
+--let before_copy_test_t10=DROP TABLE test.t10
+--let wait_innodb_redo_before_copy=test/t10
 
-exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$incremental_dir --incremental-basedir=$basedir --dbug=+d,mariabackup_events;
+# mariabackup should crash with assertion if MDEV-24026 is not fixed
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir=$incremental_dir --incremental-basedir=$basedir --dbug=+d,mariabackup_events,mariabackup_inject_code;
 --let after_load_tablespaces=
 --disable_result_log
 echo # Prepare full backup, apply incremental one;