ext4: don't count free clusters from a corrupt block group

A bg that's been flagged "corrupt" by definition has no free blocks,
so that the allocator won't be tempted to use the damaged bg.
Therefore, we shouldn't count the clusters in the damaged group when
calculating free counts.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index dc5d572..6ea7b14 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -640,6 +640,7 @@
 	struct ext4_group_desc *gdp;
 	ext4_group_t i;
 	ext4_group_t ngroups = ext4_get_groups_count(sb);
+	struct ext4_group_info *grp;
 #ifdef EXT4FS_DEBUG
 	struct ext4_super_block *es;
 	ext4_fsblk_t bitmap_count;
@@ -655,7 +656,11 @@
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
 			continue;
-		desc_count += ext4_free_group_clusters(sb, gdp);
+		grp = NULL;
+		if (EXT4_SB(sb)->s_group_info)
+			grp = ext4_get_group_info(sb, i);
+		if (!grp || !EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
+			desc_count += ext4_free_group_clusters(sb, gdp);
 		brelse(bitmap_bh);
 		bitmap_bh = ext4_read_block_bitmap(sb, i);
 		if (bitmap_bh == NULL)
@@ -679,7 +684,11 @@
 		gdp = ext4_get_group_desc(sb, i, NULL);
 		if (!gdp)
 			continue;
-		desc_count += ext4_free_group_clusters(sb, gdp);
+		grp = NULL;
+		if (EXT4_SB(sb)->s_group_info)
+			grp = ext4_get_group_info(sb, i);
+		if (!grp || !EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
+			desc_count += ext4_free_group_clusters(sb, gdp);
 	}
 
 	return desc_count;