MDEV-13603 innodb_fast_shutdown=0 may fail to purge all history

srv_purge_should_exit(): Remove the parameter n_purged.
If we happened to have n_purged==0 while some transaction was still
active, and then that transaction was added to the history list,
we were prematurely stopping the purge. It is more appropriate to
first check for trx_sys.any_active_transactions() == 0
(this count can only decrease during shutdown) and then for
trx_sys.history_size() == 0 (that count typically decreases, but
can increase when any remaining active transactions are committed
or rolled back).

innodb.dml_purge: Remove a server restart, and explicitly wait for
purge, and use FLUSH TABLE FOR EXPORT to read the file contents.
This will make the test run faster, easier to debug, and also
allow it to run with --embedded. This might also help repeat
MDEV-11802 better. The issue MDEV-13603 remains will remain tested
by innodb.table_flags.

mysql-test/suite/innodb/r/dml_purge.result

+SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 #
 # MDEV-12288 Reset DB_TRX_ID when the history is removed,
 # to speed up MVCC
@@ -7,7 +9,8 @@ CREATE TABLE t1(a INT PRIMARY KEY, b INT NOT NULL)
 ROW_FORMAT=REDUNDANT ENGINE=InnoDB;
 INSERT INTO t1 VALUES(1,2),(3,4);
 UPDATE t1 SET b=-3 WHERE a=3;
-SET GLOBAL innodb_fast_shutdown=0;
+InnoDB		0 transactions not purged
+FLUSH TABLE t1 FOR EXPORT;
 Clustered index root page contents:
 N_RECS=2; LEVEL=0
 header=0x010000030087 (a=0x696e66696d756d00)
@@ -20,8 +23,10 @@ header=0x000018090074 (a=0x80000003,
  DB_ROLL_PTR=0x80000000000000,
  b=0x7ffffffd)
 header=0x030008030000 (a=0x73757072656d756d00)
+UNLOCK TABLES;
 SELECT * FROM t1;
 a	b
 1	2
 3	-3
 DROP TABLE t1;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;

mysql-test/suite/innodb/t/dml_purge.test

 --source include/innodb_page_size.inc
---source include/not_embedded.inc
 
 let INNODB_PAGE_SIZE=`select @@innodb_page_size`;
 let MYSQLD_DATADIR=`select @@datadir`;
+SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 
 --echo #
 --echo # MDEV-12288 Reset DB_TRX_ID when the history is removed,
@@ -13,12 +14,14 @@ SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 
 CREATE TABLE t1(a INT PRIMARY KEY, b INT NOT NULL)
 ROW_FORMAT=REDUNDANT ENGINE=InnoDB;
+
 INSERT INTO t1 VALUES(1,2),(3,4);
 UPDATE t1 SET b=-3 WHERE a=3;
 
 # Initiate a full purge, which should reset all DB_TRX_ID.
-SET GLOBAL innodb_fast_shutdown=0;
---source include/shutdown_mysqld.inc
+--source include/wait_all_purged.inc
+
+FLUSH TABLE t1 FOR EXPORT;
 # The following is based on innodb.table_flags:
 --perl
 use strict;
@@ -54,6 +57,7 @@ for (my $offset= 0x65; $offset;
 }
 close(FILE) || die "Unable to close $file\n";
 EOF
---source include/start_mysqld.inc
+UNLOCK TABLES;
 SELECT * FROM t1;
 DROP TABLE t1;
+SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;

storage/innobase/srv/srv0srv.cc

@@ -2446,12 +2446,8 @@ DECLARE_THREAD(srv_master_thread)(
 	goto loop;
 }
 
-/** Check if purge should stop.
-@param[in]	n_purged	pages purged in the last batch
-@return whether purge should exit */
-static
-bool
-srv_purge_should_exit(ulint n_purged)
+/** @return whether purge should exit due to shutdown */
+static bool srv_purge_should_exit()
 {
 	ut_ad(srv_shutdown_state == SRV_SHUTDOWN_NONE
 	      || srv_shutdown_state == SRV_SHUTDOWN_CLEANUP);
@@ -2463,12 +2459,7 @@ srv_purge_should_exit(ulint n_purged)
 		return(true);
 	}
 	/* Slow shutdown was requested. */
-	if (n_purged) {
-		/* The previous round still did some work. */
-		return(false);
-	}
-	/* Exit if there are no active transactions to roll back. */
-	return(trx_sys.any_active_transactions() == 0);
+	return !trx_sys.any_active_transactions() && !trx_sys.history_size();
 }
 
 /*********************************************************************//**
@@ -2643,9 +2634,9 @@ srv_do_purge(ulint* n_total_purged)
 
 		*n_total_purged += n_pages_purged;
 
-	} while (!srv_purge_should_exit(n_pages_purged)
-		 && n_pages_purged > 0
-		 && purge_sys.state == PURGE_STATE_RUN);
+	} while (n_pages_purged > 0
+		 && purge_sys.state == PURGE_STATE_RUN
+		 && !srv_purge_should_exit());
 
 	return(rseg_history_len);
 }
@@ -2776,14 +2767,14 @@ DECLARE_THREAD(srv_purge_coordinator_thread)(
 
 		ut_ad(!slot->suspended);
 
-		if (srv_purge_should_exit(n_total_purged)) {
+		if (srv_purge_should_exit()) {
 			break;
 		}
 
 		n_total_purged = 0;
 
 		rseg_history_len = srv_do_purge(&n_total_purged);
-	} while (!srv_purge_should_exit(n_total_purged));
+	} while (!srv_purge_should_exit());
 
 	/* The task queue should always be empty, independent of fast
 	shutdown state. */