btrfs-progs: tests/fsck: add test case for data csum check on raid5

Previously 'btrfs check --check-data-csum' will report tons of false
alerts for RAID56.

Add a test case to make sure with the new RAID56 rebuild ability, there
should be no false alerts.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

tests/fsck-tests/056-raid56-false-alerts/test.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+#
+# Make sure "btrfs check --check-data-csum" won't report false alerts on RAID56
+# data.
+#
+
+source "$TEST_TOP/common"
+
+check_prereq btrfs
+check_prereq mkfs.btrfs
+check_global_prereq losetup
+
+setup_loopdevs 3
+prepare_loopdevs
+dev1=${loopdevs[1]}
+TEST_DEV=$dev1
+
+setup_root_helper
+
+run_check $SUDO_HELPER "$TOP/mkfs.btrfs" -f -m raid1 -d raid5 "${loopdevs[@]}"
+run_check_mount_test_dev
+
+run_check $SUDO_HELPER dd if=/dev/urandom of="$TEST_MNT/file" bs=16K count=1 \
+	status=noxfer > /dev/null 2>&1
+
+run_check_umount_test_dev
+
+# Check data csum should not report false alerts
+run_check "$TOP/btrfs" check --check-data-csum "$dev1"
+
+cleanup_loopdevs