Btrfs: don't add extent 0 to the free space cache v2

If block group 0 is completely free, btrfs_read_block_groups will
add extent [0, BTRFS_SUPER_INFO_OFFSET) to the free space cache.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 44d7a322ec28..39761ca07f15 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -195,6 +195,14 @@ static int exclude_super_stripes(struct btrfs_root *root,
         int stripe_len;
         int i, nr, ret;
 
+        if (cache->key.objectid < BTRFS_SUPER_INFO_OFFSET) {
+                stripe_len = BTRFS_SUPER_INFO_OFFSET - cache->key.objectid;
+                cache->bytes_super += stripe_len;
+                ret = add_excluded_extent(root, cache->key.objectid,
+                                          stripe_len);
+                BUG_ON(ret);
+        }
+
         for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
                 bytenr = btrfs_sb_offset(i);
                 ret = btrfs_rmap_block(&root->fs_info->mapping_tree,
@@ -255,7 +263,7 @@ static u64 add_new_free_space(struct btrfs_block_group_cache *block_group,
                 if (ret)
                         break;
 
-                if (extent_start == start) {
+                if (extent_start <= start) {
                         start = extent_end + 1;
                 } else if (extent_start > start && extent_start < end) {
                         size = extent_start - start;