ext4: hold group lock in ext4 kunit test

Although there is no concurrent block allocation/free in unit test,
internal functions mb_mark_used and mb_free_blocks assert group
lock is always held. Acquire group before calling mb_mark_used and
mb_free_blocks in unit test to avoid the assertion.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240304163543.6700-3-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Kemeng Shi

fs/ext4/mballoc-test.c

@@ -716,7 +716,10 @@ test_mb_mark_used_range(struct kunit *test, struct ext4_buddy *e4b,
 	ex.fe_start = start;
 	ex.fe_len = len;
 	ex.fe_group = TEST_GOAL_GROUP;
+
+	ext4_lock_group(sb, TEST_GOAL_GROUP);
 	mb_mark_used(e4b, &ex);
+	ext4_unlock_group(sb, TEST_GOAL_GROUP);
 
 	mb_set_bits(bitmap, start, len);
 	/* bypass bb_free validatoin in ext4_mb_generate_buddy */
@@ -776,7 +779,9 @@ test_mb_free_blocks_range(struct kunit *test, struct ext4_buddy *e4b,
 	if (len == 0)
 		return;
 
+	ext4_lock_group(sb, e4b->bd_group);
 	mb_free_blocks(NULL, e4b, start, len);
+	ext4_unlock_group(sb, e4b->bd_group);
 
 	mb_clear_bits(bitmap, start, len);
 	/* bypass bb_free validatoin in ext4_mb_generate_buddy */
@@ -820,7 +825,11 @@ static void test_mb_free_blocks(struct kunit *test)
 	ex.fe_start = 0;
 	ex.fe_len = EXT4_CLUSTERS_PER_GROUP(sb);
 	ex.fe_group = TEST_GOAL_GROUP;
+
+	ext4_lock_group(sb, TEST_GOAL_GROUP);
 	mb_mark_used(&e4b, &ex);
+	ext4_unlock_group(sb, TEST_GOAL_GROUP);
+
 	grp->bb_free = 0;
 	memset(bitmap, 0xff, sb->s_blocksize);