MDEV-35394 Innochecksum misinterprets freed pages

- Innochecksum misinterprets the freed pages as active one.
This leads the user to think there are too many valid
pages exist.

- To avoid this confusion, innochecksum introduced one
more option --skip-freed-pages and -r to avoid the freed
pages while dumping or printing the summary of the tablespace.

- Innochecksum can safely assume the page is freed if
the respective extent doesn't belong to a segment and marked as
freed in XDES_BITMAP in extent descriptor page.

- Innochecksum shouldn't assume that zero-filled page as extent
descriptor page.

extra/innochecksum.cc

@@ -100,6 +100,8 @@ FILE*				log_file = NULL;
 /* Enabled for log write option. */
 static bool			is_log_enabled = false;
 
+/* Skip freed pages */
+static bool			skip_freed_pages= false;
 static byte field_ref_zero_buf[UNIV_PAGE_SIZE_MAX];
 const byte *field_ref_zero = field_ref_zero_buf;
 
@@ -786,6 +788,16 @@ parse_page(
 
 	/* Check whether page is doublewrite buffer. */
 	str = skip_page ? "Double_write_buffer" : "-";
+	page_no = mach_read_from_4(page + FIL_PAGE_OFFSET);
+	if (skip_freed_pages) {
+		const byte *des= xdes + XDES_ARR_OFFSET +
+			XDES_SIZE * ((page_no & (physical_page_size - 1))
+				     / FSP_EXTENT_SIZE);
+		if (mach_read_from_4(des) != XDES_FSEG &&
+		    xdes_is_free(des, page_no % FSP_EXTENT_SIZE)) {
+			return;
+		}
+	}
 
 	switch (fil_page_get_type(page)) {
 
@@ -1211,6 +1223,9 @@ static struct my_option innochecksum_options[] = {
     &do_leaf, &do_leaf, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
   {"merge", 'm', "leaf page count if merge given number of consecutive pages",
    &n_merge, &n_merge, 0, GET_ULONG, REQUIRED_ARG, 0, 0, (longlong)10L, 0, 1, 0},
+  {"skip-freed-pages", 'r', "skip freed pages for the tablespace",
+   &skip_freed_pages, &skip_freed_pages, 0, GET_BOOL, NO_ARG,
+   0, 0, 0, 0, 0, 0},
 
   {0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
 };
@@ -1288,6 +1303,9 @@ innochecksum_get_one_option(
 	case 'l':
 		is_log_enabled = true;
 		break;
+	case 'r':
+		skip_freed_pages = true;
+		break;
 	case 'I':
 	case '?':
 		usage();
@@ -1861,7 +1879,7 @@ int main(
 				printf("page " UINT32PF " ", cur_page_num);
 			}
 
-			if (page_get_page_no(buf) % physical_page_size == 0) {
+			if (cur_page_num % physical_page_size == 0) {
 				memcpy(xdes, buf, physical_page_size);
 			}
 

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

@@ -0,0 +1,7 @@
+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+CREATE TABLE t1(f1 INT NOT NULL)ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1);
+DROP TABLE t1;
+SET GLOBAL innodb_fast_shutdown=0;
+FOUND 1 /Undo page state: 0 active, 0 cached, 0 to_purge, 0 prepared, 0 other/ in result.log
+# restart

mysql-test/suite/innodb/t/innochecksum_undo_page.opt

@@ -0,0 +1 @@
+--innodb_undo_tablespaces=0

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

@@ -0,0 +1,18 @@
+--source include/have_innodb.inc
+--source include/not_embedded.inc
+let MYSQLD_DATADIR= `SELECT @@datadir`;
+
+SET GLOBAL INNODB_FILE_PER_TABLE= 0;
+CREATE TABLE t1(f1 INT NOT NULL)ENGINE=InnoDB;
+INSERT INTO t1 VALUES(1);
+DROP TABLE t1;
+SET GLOBAL innodb_fast_shutdown=0;
+--source include/shutdown_mysqld.inc
+let $resultlog=$MYSQLTEST_VARDIR/tmp/result.log;
+exec $INNOCHECKSUM -S -r $MYSQLD_DATADIR/ibdata1 > $resultlog;
+
+let SEARCH_FILE = $MYSQLTEST_VARDIR/tmp/result.log;
+let SEARCH_PATTERN= Undo page state: 0 active, 0 cached, 0 to_purge, 0 prepared, 0 other;
+--source include/search_pattern_in_file.inc
+--remove_file $resultlog
+--source include/start_mysqld.inc

mysql-test/suite/innodb_zip/r/innochecksum_3.result

@@ -139,6 +139,7 @@ per-page-details                  FALSE
 log                               (No default value)
 leaf                              FALSE
 merge                             0
+skip-freed-pages                  FALSE
 [5]: Page type dump for with shortform for tab1.ibd