MDEV-30949 Direct leak in binlog_online_alter_end_trans

when committing a big transaction, online_alter_cache_log creates a cache
file. It wasn't properly closed, which was spotted by a memory leak from
my_register_filename. A temporary file also remained open.

Binlog wasn't affected by this, since it features its own file management.

A proper closing is calling close_cached_file. It deinits io_cache and
closes the underlying file. After closing, the file is expected to be
deleted automagically.

mysql-test/main/alter_table_online_debug.result

@@ -1296,6 +1296,22 @@ connection default;
 select * from t;
 a	b	c
 drop table t;
+#
+# MDEV-30949 Direct leak in binlog_online_alter_end_trans
+#
+create table t (f longblob default null) engine=myisam;
+insert into t values (null);
+set debug_sync= "alter_table_copy_end signal copy wait_for goon";
+set debug_sync= "alter_table_online_before_lock signal lock wait_for end";
+alter table t force, algorithm=copy;
+connection con1;
+set debug_sync= "now wait_for copy";
+insert into t select repeat('a',130000);
+set debug_sync= "now signal goon wait_for lock";
+insert into t select repeat('a',130000);
+set debug_sync= "now signal end";
+connection default;
+drop table t;
 set debug_sync= reset;
 disconnect con1;
 disconnect con2;

mysql-test/main/alter_table_online_debug.test

@@ -1475,6 +1475,30 @@ dec $i;
 let local_engine=aria;
 }
 
+--echo #
+--echo # MDEV-30949 Direct leak in binlog_online_alter_end_trans
+--echo #
+create table t (f longblob default null) engine=myisam;
+insert into t values (null);
+
+set debug_sync= "alter_table_copy_end signal copy wait_for goon";
+set debug_sync= "alter_table_online_before_lock signal lock wait_for end";
+
+send alter table t force, algorithm=copy;
+
+--connection con1
+set debug_sync= "now wait_for copy";
+insert into t select repeat('a',130000);
+set debug_sync= "now signal goon wait_for lock";
+insert into t select repeat('a',130000);
+set debug_sync= "now signal end";
+
+
+--connection default
+--reap
+drop table t;
+
+
 set debug_sync= reset;
 --disconnect con1
 --disconnect con2

sql/log.h

@@ -512,7 +512,8 @@ class Cache_flip_event_log: public Event_log {
 private:
   void cleanup()
   {
-    end_io_cache(&alt_buf);
+    close_cached_file(&log_file);
+    close_cached_file(&alt_buf);
     Event_log::cleanup();
   }
 };