diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index db9075f397d1822d719ee1be232d6ed5661f8d31..b2e22a84a7043abac24add7f6f35bd2362905d1c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -841,30 +841,30 @@ static void
 mb_update_avg_fragment_size(struct super_block *sb, struct ext4_group_info *grp)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	int new_order;
+	int new, old;
 
-	if (!test_opt2(sb, MB_OPTIMIZE_SCAN) || grp->bb_fragments == 0)
+	if (!test_opt2(sb, MB_OPTIMIZE_SCAN))
 		return;
 
-	new_order = mb_avg_fragment_size_order(sb,
-					grp->bb_free / grp->bb_fragments);
-	if (new_order == grp->bb_avg_fragment_size_order)
+	old = grp->bb_avg_fragment_size_order;
+	new = grp->bb_fragments == 0 ? -1 :
+	      mb_avg_fragment_size_order(sb, grp->bb_free / grp->bb_fragments);
+	if (new == old)
 		return;
 
-	if (grp->bb_avg_fragment_size_order != -1) {
-		write_lock(&sbi->s_mb_avg_fragment_size_locks[
-					grp->bb_avg_fragment_size_order]);
+	if (old >= 0) {
+		write_lock(&sbi->s_mb_avg_fragment_size_locks[old]);
 		list_del(&grp->bb_avg_fragment_size_node);
-		write_unlock(&sbi->s_mb_avg_fragment_size_locks[
-					grp->bb_avg_fragment_size_order]);
-	}
-	grp->bb_avg_fragment_size_order = new_order;
-	write_lock(&sbi->s_mb_avg_fragment_size_locks[
-					grp->bb_avg_fragment_size_order]);
-	list_add_tail(&grp->bb_avg_fragment_size_node,
-		&sbi->s_mb_avg_fragment_size[grp->bb_avg_fragment_size_order]);
-	write_unlock(&sbi->s_mb_avg_fragment_size_locks[
-					grp->bb_avg_fragment_size_order]);
+		write_unlock(&sbi->s_mb_avg_fragment_size_locks[old]);
+	}
+
+	grp->bb_avg_fragment_size_order = new;
+	if (new >= 0) {
+		write_lock(&sbi->s_mb_avg_fragment_size_locks[new]);
+		list_add_tail(&grp->bb_avg_fragment_size_node,
+				&sbi->s_mb_avg_fragment_size[new]);
+		write_unlock(&sbi->s_mb_avg_fragment_size_locks[new]);
+	}
 }
 
 /*