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>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 44d7a32..39761ca 100644 (file)
--- 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;