Bug #27322 failure to allocate transaction_prealloc_size causes crash

Fix for when memory pre-allocation fails.

mysql-test/r/bdb_notembedded.result

+set autocommit=1;
+reset master;
+create table bug16206 (a int);
+insert into bug16206 values(1);
+start transaction;
+insert into bug16206 values(2);
+commit;
+show binlog events;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+f	n	Format_desc	1	n	Server ver: VERSION, Binlog ver: 4
+f	n	Query	1	n	use `test`; create table bug16206 (a int)
+f	n	Query	1	n	use `test`; insert into bug16206 values(1)
+f	n	Query	1	n	use `test`; insert into bug16206 values(2)
+drop table bug16206;
+reset master;
+create table bug16206 (a int) engine=         bdb;
+insert into bug16206 values(0);
+insert into bug16206 values(1);
+start transaction;
+insert into bug16206 values(2);
+commit;
+insert into bug16206 values(3);
+show binlog events;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+f	n	Format_desc	1	n	Server ver: VERSION, Binlog ver: 4
+f	n	Query	1	n	use `test`; create table bug16206 (a int) engine=         bdb
+f	n	Query	1	n	use `test`; insert into bug16206 values(0)
+f	n	Query	1	n	use `test`; insert into bug16206 values(1)
+f	n	Query	1	n	use `test`; BEGIN
+f	n	Query	1	n	use `test`; insert into bug16206 values(2)
+f	n	Query	1	n	use `test`; COMMIT
+f	n	Query	1	n	use `test`; insert into bug16206 values(3)
+drop table bug16206;
+set autocommit=0;
+End of 5.0 tests

mysql-test/r/variables-big.result

+set session transaction_prealloc_size=1024*1024*1024*1;
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+1	root	localhost	test	Query	0	NULL	show processlist
+set session transaction_prealloc_size=1024*1024*1024*2;
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+1	root	localhost	test	Query	2	NULL	show processlist
+set session transaction_prealloc_size=1024*1024*1024*3;
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+1	root	localhost	test	Query	0	NULL	show processlist
+set session transaction_prealloc_size=1024*1024*1024*4;
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+1	root	localhost	test	Query	0	NULL	show processlist
+set session transaction_prealloc_size=1024*1024*1024*5;
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+1	root	localhost	test	Query	0	NULL	show processlist

mysql-test/t/bdb_notembedded.test

+-- source include/not_embedded.inc
+-- source include/have_bdb.inc
+
+#
+# Bug #16206: Superfluous COMMIT event in binlog when updating BDB in autocommit mode
+#
+set autocommit=1;
+
+let $VERSION=`select version()`;
+
+reset master;
+create table bug16206 (a int);
+insert into bug16206 values(1);
+start transaction;
+insert into bug16206 values(2);
+commit;
+--replace_result $VERSION VERSION
+--replace_column 1 f 2 n 5 n
+show binlog events;
+drop table bug16206;
+
+reset master;
+create table bug16206 (a int) engine=         bdb;
+insert into bug16206 values(0);
+insert into bug16206 values(1);
+start transaction;
+insert into bug16206 values(2);
+commit;
+insert into bug16206 values(3);
+--replace_result $VERSION VERSION
+--replace_column 1 f 2 n 5 n
+show binlog events;
+drop table bug16206;
+
+set autocommit=0;
+
+
+--echo End of 5.0 tests

mysql-test/t/variables-big.test

+#
+# test variables big
+#
+
+--source include/big_test.inc
+
+#
+# Bug #27322  	failure to allocate transaction_prealloc_size causes crash
+#
+
+set session transaction_prealloc_size=1024*1024*1024*1;
+show processlist;
+set session transaction_prealloc_size=1024*1024*1024*2;
+show processlist;
+set session transaction_prealloc_size=1024*1024*1024*3;
+show processlist;
+set session transaction_prealloc_size=1024*1024*1024*4;
+show processlist;
+set session transaction_prealloc_size=1024*1024*1024*5;
+show processlist;

mysys/my_alloc.c

@@ -133,6 +133,10 @@ void reset_root_defaults(MEM_ROOT *mem_root, uint block_size,
         mem->next= *prev;
         *prev= mem_root->pre_alloc= mem; 
       }
+      else
+      {
+        mem_root->pre_alloc= 0;
+      }
     }
   }
   else