ext4: get correct ext4_group_info in ext4_mb_prefetch_fini

We always get ext4_group_desc with group + 1 and ext4_group_info with
group to check if we need do initialize ext4_group_info for the group.
Just get ext4_group_desc with group for ext4_group_info initialization
check.
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20230303172120.3800725-4-shikemeng@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -2569,14 +2569,14 @@ ext4_group_t ext4_mb_prefetch(struct super_block *sb, ext4_group_t group,
 void ext4_mb_prefetch_fini(struct super_block *sb, ext4_group_t group,
 			   unsigned int nr)
 {
-	while (nr-- > 0) {
-		struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group,
-								  NULL);
-		struct ext4_group_info *grp = ext4_get_group_info(sb, group);
+	struct ext4_group_desc *gdp;
+	struct ext4_group_info *grp;
 
+	while (nr-- > 0) {
 		if (!group)
 			group = ext4_get_groups_count(sb);
 		group--;
+		gdp = ext4_get_group_desc(sb, group, NULL);
 		grp = ext4_get_group_info(sb, group);
 
 		if (EXT4_MB_GRP_NEED_INIT(grp) &&