btrfs-progs: tests: tests: add a test case for convert with bgt feature

Previously "btrfs-convert -O bgt" would not cause any error, but the
resulting fs has no block-group-tree feature at all, making it no
different than "btrfs-convert -O ^bgt".

This is a big bug that was never caught by our existing convert runs.
001-ext2-basic and 003-ext4-basic all tested bgt feature, but don't
really check if the resulting fs really have bgt flags set.

To fix that add a new test case, which will do the regular bgt convert,
but at the end also do a super block dump and verify the
BLOCK_GROUP_TREE flag is properly set.

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

Author: adam900710

tests/convert-tests/028-block-group-tree/test.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Make sure btrfs-convert can create a fs with bgt feature.
+
+source "$TEST_TOP/common" || exit
+source "$TEST_TOP/common.convert" || exit
+
+setup_root_helper
+prepare_test_dev
+
+check_global_prereq mkfs.ext4
+check_prereq btrfs-convert
+check_prereq btrfs
+
+convert_test_prep_fs ext4 mke2fs -t ext4 -b 4096
+run_check_umount_test_dev
+convert_test_do_convert bgt 16384
+
+# Manually check the super block to make sure it has BGT flag.
+run_check_stdout "$TOP/btrfs" inspect-internal dump-super "$TEST_DEV" |\
+	grep -q "BLOCK_GROUP_TREE" || _fail "No block-group-tree feature enabled"