MDEV-36270 mariabackup.incremental_compressed fails in 10.11+

Problem:
=======
- During prepare of incremental backup, mariabackup does create
new file in target directory with default file size of
4 * innodb_page_size. While applying .delta file to corresponding
data file, it encounters the FSP_SIZE modification on page0 and
tries to extend the file to the size which is 4 in our case.
Since the table is in compressed row format, page_size for the
table is 8k. This lead to shrinking of tablespace file from 65536 to
32768. This issue happens only in windows because os_file_set_size()
doesn't check for the current size and shrinks the file.

Solution:
==========
xtrabackup_apply_delta(): Check for the current size before doing setting
size for the file.

Author: Thirunarayanan

extra/mariabackup/xtrabackup.cc

@@ -6250,9 +6250,14 @@ xtrabackup_apply_delta(
 					buf + FSP_HEADER_OFFSET + FSP_SIZE);
 				if (mach_read_from_4(buf
 						     + FIL_PAGE_SPACE_ID)) {
-					if (!os_file_set_size(
-						    dst_path, dst_file,
-						    n_pages * page_size))
+					os_offset_t last_page =
+					  os_file_get_size(dst_file) /
+					  page_size;
+
+					if (last_page < n_pages &&
+					    !os_file_set_size(
+					       dst_path, dst_file,
+					       n_pages * page_size))
 						goto error;
 				} else if (fil_space_t* space
 					   = fil_system.sys_space) {

mysql-test/suite/mariabackup/incremental_compressed.result

@@ -4,6 +4,9 @@
 #
 CREATE TABLE t (pk INT PRIMARY KEY) ENGINE=InnoDB ROW_FORMAT=COMPRESSED;
 ALTER TABLE t PARTITION BY KEY(pk);
+# Incremental backup
+# Prepare fullbackup
+# Prepare incremental backup
 # shutdown server
 # remove datadir
 # xtrabackup move back

mysql-test/suite/mariabackup/incremental_compressed.test

@@ -16,12 +16,18 @@ CREATE TABLE t (pk INT PRIMARY KEY) ENGINE=InnoDB ROW_FORMAT=COMPRESSED;
 
 ALTER TABLE t PARTITION BY KEY(pk);
 
+--echo # Incremental backup
 --exec $XTRABACKUP --backup --target-dir=$incremental_dir --incremental-basedir=$basedir --protocol=tcp --port=$MASTER_MYPORT --user=root > $incremental_dir.log 2>&1
+--echo # Prepare fullbackup
 --exec $XTRABACKUP --prepare --target-dir=$basedir --user=root > $MYSQL_TMP_DIR/backup_prepare_0.log 2>&1
---exec $XTRABACKUP --prepare --target-dir=$basedir --incremental-dir=$incremental_dir --user=root >  $MYSQL_TMP_DIR/backup_prepare_1.log
---cat_file $MYSQL_TMP_DIR/backup_prepare_1.log
+--echo # Prepare incremental backup
+--exec $XTRABACKUP --prepare --target-dir=$basedir --incremental-dir=$incremental_dir --user=root >  $MYSQL_TMP_DIR/backup_prepare_1.log 2>&1
 let $targetdir=$basedir;
 -- source include/restart_and_restore.inc
-
 SHOW CREATE TABLE t;
 DROP TABLE t;
+remove_file $incremental_dir.log;
+remove_file $MYSQL_TMP_DIR/backup_prepare_0.log;
+remove_file $MYSQL_TMP_DIR/backup_prepare_1.log;
+rmdir $basedir;
+rmdir $incremental_dir;