--- linux-4.18/fs/ext4/mballoc.c	2019-11-28 14:55:26.500545920 +0300
+++ linux-4.18/fs/ext4/mballoc.c	2019-11-28 14:53:18.600086008 +0300
@@ -1885,6 +1885,21 @@ void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,

 	return 0;
 }
+
+static inline int ext4_mb_uninit_on_disk(struct super_block *sb,
+				    ext4_group_t group)
+{
+	struct ext4_group_desc *desc;
+
+	if (!ext4_has_group_desc_csum(sb))
+		return 0;
+
+	desc = ext4_get_group_desc(sb, group, NULL);
+	if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))
+		return 1;
+
+	return 0;
+}

 /*
  * The routine scans buddy structures (not bitmap!) from given order
@@ -2060,7 +2060,15 @@ static int ext4_mb_good_group(struct
 
 	/* We only do this if the grp has never been initialized */
 	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
-		int ret = ext4_mb_init_group(ac->ac_sb, group);
+		int ret;
+
+		/* cr=0/1 is a very optimistic search to find large
+		 * good chunks almost for free. if buddy data is
+		 * not ready, then this optimization makes no sense */
+
+		if (cr < 2 && !ext4_mb_uninit_on_disk(ac->ac_sb, group))
+			return 0;
+		ret = ext4_mb_init_group(ac->ac_sb, group);
 		if (ret)
 			return ret;
 	}