Fix mariabackup InnoDB recovered binlog position on server upgrade

Before MariaDB 10.3.5, the binlog position was stored in the TRX_SYS page,
while after it is stored in rollback segments. There is code to read the
legacy position from TRX_SYS to handle upgrades. The problem was if the
legacy position happens to compare larger than the position found in
rollback segments; in this case, the old TRX_SYS position would incorrectly
be preferred over the newer position from rollback segments.

Fixed by always preferring a position from rollback segments over a legacy
position.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

mysql-test/suite/innodb/include/crc32.pl

@@ -31,3 +31,26 @@ sub mycrc32 {
 
  return $crc;
 }
+
+
+# Fix the checksum of an InnoDB tablespace page.
+# Inputs:
+#   $page        A bytestring with the page data.
+#   $full_crc32  Checksum type, see get_full_crc32() in innodb-util.pl
+# Returns: the modified page as a bytestring.
+sub fix_page_crc {
+  my ($page, $full_crc32)= @_;
+  my $ps= length($page);
+  my $polynomial = 0x82f63b78; # CRC-32C
+  if ($full_crc32) {
+    my $ck = mycrc32(substr($page, 0, $ps - 4), 0, $polynomial);
+    substr($page, $ps - 4, 4) = pack("N", $ck);
+  } else {
+    my $ck= pack("N",
+                 mycrc32(substr($page, 4, 22), 0, $polynomial) ^
+                 mycrc32(substr($page, 38, $ps - 38 - 8), 0, $polynomial));
+    substr($page, 0, 4)= $ck;
+    substr($page, $ps-8, 4)= $ck;
+  }
+  return $page;
+}

mysql-test/suite/innodb/include/innodb-util.pl

@@ -124,3 +124,22 @@ sub ib_restore_ibd_files {
         ib_restore_ibd_file($tmpd, $datadir, $db, $table);
     }
 }
+
+# Read the flag whether a tablespace is using full_crc32.
+# Input: filehandle opened on the tablespace.
+sub get_full_crc32 {
+    my ($TBLSPC)= @_;
+    my $old_pos= sysseek($TBLSPC, 0, 1);
+    die "tell() failed on tablespace filehandle: $!\n"
+        unless defined($old_pos);
+    sysseek($TBLSPC, 0, 0)
+        or die "sysseek() failed on tablespace filehandle: $!\n";
+    my $tblspc_hdr;
+    sysread($TBLSPC, $tblspc_hdr, 58)
+        or die "Cannot read tablespace header: $!\n";
+    sysseek($TBLSPC, $old_pos, 0)
+        or die "sysseek() failed on tablespace filehandle: $!\n";
+    my $full_crc32=
+        unpack("N", substr($tblspc_hdr, 54, 4)) & 0x10; # FIL_SPACE_FLAGS
+    return $full_crc32;
+}

mysql-test/suite/mariabackup/slave_provision_nolock.result

+# restart
 RESET MASTER;
 CREATE TABLE t1(a varchar(60) PRIMARY KEY, b VARCHAR(60)) ENGINE INNODB;
 INSERT INTO t1 VALUES(1, NULL);

mysql-test/suite/mariabackup/slave_provision_nolock.test

@@ -3,6 +3,58 @@
 
 # Test provisioning a slave from an existing server, using mariabackup --no-lock
 # and the binlog position recovered from InnoDB redo log.
+
+# Update the InnoDB system tablespace to simulate a pre-10.3.5
+# position in TRX_SYS. There was a bug that the wrong position could
+# be recovered if the old filename in TRX_SYS compares newer than the
+# newer filenames stored in rseg headers.
+let MYSQLD_DATADIR=`select @@datadir`;
+let INNODB_PAGE_SIZE=`select @@innodb_page_size`;
+
+--source include/shutdown_mysqld.inc
+
+--perl
+use strict;
+use warnings;
+use Fcntl qw(:DEFAULT :seek);
+do "$ENV{MTR_SUITE_DIR}/../innodb/include/crc32.pl";
+do "$ENV{MTR_SUITE_DIR}/../innodb/include/innodb-util.pl";
+
+my $ps = $ENV{INNODB_PAGE_SIZE};
+
+sysopen IBD_FILE, "$ENV{MYSQLD_DATADIR}/ibdata1", O_RDWR
+  or die "Cannot open ibdata1: $!\n";
+
+# Read the TRX_SYS page.
+my $page;
+sysseek(IBD_FILE, $ps * 5, SEEK_SET)
+  or die "Cannot seek ibdata1: $!\n";
+sysread(IBD_FILE, $page, $ps)
+  or die "Cannot read ibdata1: $!\n";
+
+# Put in an old binlog position that will compare larger than master-bin.000001
+my $old_name= '~~~-bin.999999' . chr(0);
+my $old_off= 0xffff0000;
+my $old_magic= 873422344;
+my $binlog_offset= $ps - 1000 + 38;
+substr($page, $binlog_offset, 4)= pack('N', $old_magic);
+substr($page, $binlog_offset + 4, 4)= pack('N', ($old_off >> 32));
+substr($page, $binlog_offset + 8, 4)= pack('N', ($old_off & 0xffffffff));
+substr($page, $binlog_offset + 12, length($old_name))= $old_name;
+
+# Write back the modified page.
+my $full_crc32= get_full_crc32(\*IBD_FILE);
+my $page= fix_page_crc($page, $full_crc32);
+sysseek(IBD_FILE, $ps * 5, SEEK_SET)
+  or die "Cannot seek ibdata1: $!\n";
+syswrite(IBD_FILE, $page, $ps) == $ps
+  or die "Cannot write ibdata1: $!\n";
+close IBD_FILE;
+EOF
+
+--source include/start_mysqld.inc
+
+
 let $basedir=$MYSQLTEST_VARDIR/tmp/backup;
 
 RESET MASTER;

storage/innobase/include/trx0sys.h

@@ -867,6 +867,8 @@ class trx_sys_t
   uint64_t recovered_binlog_offset;
   /** Latest recovered binlog file name */
   char recovered_binlog_filename[TRX_SYS_MYSQL_LOG_NAME_LEN];
+  /** Set when latest position is from pre-version 10.3.5 TRX_SYS. */
+  bool recovered_binlog_is_legacy_pos;
 
 
   /**

storage/innobase/trx/trx0rseg.cc

@@ -468,7 +468,10 @@ static dberr_t trx_rseg_mem_restore(trx_rseg_t *rseg, trx_id_t &max_trx_id,
 			compile_time_assert(TRX_RSEG_BINLOG_NAME_LEN == sizeof
 					    trx_sys.recovered_binlog_filename);
 
-			int cmp = *trx_sys.recovered_binlog_filename
+			/* Always prefer a position from rollback segment over
+			a legacy position from before version 10.3.5. */
+			int cmp = *trx_sys.recovered_binlog_filename &&
+				  !trx_sys.recovered_binlog_is_legacy_pos
 				? strncmp(binlog_name,
 					  trx_sys.recovered_binlog_filename,
 					  TRX_RSEG_BINLOG_NAME_LEN)
@@ -489,6 +492,7 @@ static dberr_t trx_rseg_mem_restore(trx_rseg_t *rseg, trx_id_t &max_trx_id,
 					trx_sys.recovered_binlog_offset
 						= binlog_offset;
 				}
+				trx_sys.recovered_binlog_is_legacy_pos= false;
 			}
 
 #ifdef WITH_WSREP
@@ -564,6 +568,7 @@ static void trx_rseg_init_binlog_info(const page_t* page)
 		trx_sys.recovered_binlog_offset = mach_read_from_8(
 			TRX_SYS_MYSQL_LOG_INFO + TRX_SYS_MYSQL_LOG_OFFSET
 			+ TRX_SYS + page);
+		trx_sys.recovered_binlog_is_legacy_pos= true;
 	}
 
 #ifdef WITH_WSREP
@@ -578,6 +583,7 @@ dberr_t trx_rseg_array_init()
 
 	*trx_sys.recovered_binlog_filename = '\0';
 	trx_sys.recovered_binlog_offset = 0;
+	trx_sys.recovered_binlog_is_legacy_pos= false;
 #ifdef WITH_WSREP
 	trx_sys.recovered_wsrep_xid.null();
 	XID wsrep_sys_xid;