MDEV-32028 InnoDB scrubbing doesn't write zero while freeing the extent

Problem:
========
InnoDB fails to mark the page status as FREED during
freeing of an extent of a segment. This behaviour affects
scrubbing and doesn't write all zeroes in file even though
pages are freed.

Solution:
========
InnoDB should mark the page status as FREED before
reinitialize the extent descriptor entry.

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

+SET @save_debug=@@GLOBAL.INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG;
+SET @save_scrub=@@GLOBAL.INNODB_IMMEDIATE_SCRUB_DATA_UNCOMPRESSED;
+SET @save_freq=@@GLOBAL.INNODB_PURGE_RSEG_TRUNCATE_FREQUENCY;
+SET GLOBAL INNODB_PURGE_RSEG_TRUNCATE_FREQUENCY=1;
+SET GLOBAL INNODB_IMMEDIATE_SCRUB_DATA_UNCOMPRESSED=1;
+SET GLOBAL INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG=2;
+CREATE TABLE t1(f1 INT AUTO_INCREMENT PRIMARY KEY,
+f2 VARCHAR(256) GENERATED ALWAYS as('repairman'),
+INDEX idx(f2))ENGINE= InnoDB;
+INSERT INTO t1(f1) SELECT seq FROM seq_1_to_50;
+FLUSH TABLE t1 FOR EXPORT;
+FOUND 108 /repairman/ in t1.ibd
+UNLOCK TABLES;
+ALTER TABLE t1 DROP INDEX idx;
+InnoDB		0 transactions not purged
+FLUSH TABLE t1 FOR EXPORT;
+NOT FOUND /repairman/ in t1.ibd
+UNLOCK TABLES;
+DROP TABLE t1;
+SET GLOBAL INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG=@save_debug;
+SET GLOBAL INNODB_IMMEDIATE_SCRUB_DATA_UNCOMPRESSED=@save_scrub;
+SET GLOBAL INNODB_PURGE_RSEG_TRUNCATE_FREQUENCY = @save_freq;

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

+--source include/have_innodb.inc
+--source include/have_sequence.inc
+--source include/have_debug.inc
+
+SET @save_debug=@@GLOBAL.INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG;
+SET @save_scrub=@@GLOBAL.INNODB_IMMEDIATE_SCRUB_DATA_UNCOMPRESSED;
+SET @save_freq=@@GLOBAL.INNODB_PURGE_RSEG_TRUNCATE_FREQUENCY;
+
+SET GLOBAL INNODB_PURGE_RSEG_TRUNCATE_FREQUENCY=1;
+SET GLOBAL INNODB_IMMEDIATE_SCRUB_DATA_UNCOMPRESSED=1;
+SET GLOBAL INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG=2;
+let $MYSQLD_DATADIR=`select @@datadir`;
+CREATE TABLE t1(f1 INT AUTO_INCREMENT PRIMARY KEY,
+		f2 VARCHAR(256) GENERATED ALWAYS as('repairman'),
+		INDEX idx(f2))ENGINE= InnoDB;
+INSERT INTO t1(f1) SELECT seq FROM seq_1_to_50;
+FLUSH TABLE t1 FOR EXPORT;
+let SEARCH_PATTERN= repairman;
+let SEARCH_FILE= $MYSQLD_DATADIR/test/t1.ibd;
+-- source include/search_pattern_in_file.inc
+UNLOCK TABLES;
+
+ALTER TABLE t1 DROP INDEX idx;
+-- source include/wait_all_purged.inc
+FLUSH TABLE t1 FOR EXPORT;
+-- source include/search_pattern_in_file.inc
+UNLOCK TABLES;
+DROP TABLE t1;
+SET GLOBAL INNODB_LIMIT_OPTIMISTIC_INSERT_DEBUG=@save_debug;
+SET GLOBAL INNODB_IMMEDIATE_SCRUB_DATA_UNCOMPRESSED=@save_scrub;
+SET GLOBAL INNODB_PURGE_RSEG_TRUNCATE_FREQUENCY = @save_freq;

storage/innobase/fsp/fsp0fsp.cc

@@ -2683,14 +2683,14 @@ fseg_free_extent(
 			      not_full_n_used - descr_n_used);
 	}
 
-	fsp_free_extent(space, page, mtr);
-
 	for (uint32_t i = 0; i < FSP_EXTENT_SIZE; i++) {
 		if (!xdes_is_free(descr, i)) {
 			buf_page_free(space, first_page_in_extent + i, mtr,
 				      __FILE__, __LINE__);
 		}
 	}
+
+	fsp_free_extent(space, page, mtr);
 }
 
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