Btrfs: fix OOPS of empty filesystem after balance

btrfs will remove unused block groups after balance.
When a empty filesystem is balanced, the block group with tag "DATA" may be
dropped, and after umount and mount again, it will not find "DATA" space_info
and lead to OOPS.
So we initial the necessary space_infos(DATA, SYSTEM, METADATA) to avoid OOPS.

Reported-by: Daniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a561060f5ffb..f619c3cb13b7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8778,6 +8778,29 @@ out:
         return ret;
 }
 
+int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_space_info *space_info;
+        int ret;
+
+        ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM, 0, 0,
+                                                                 &space_info);
+        if (ret)
+                return ret;
+
+        ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA, 0, 0,
+                                                                 &space_info);
+        if (ret)
+                return ret;
+
+        ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_DATA, 0, 0,
+                                                                 &space_info);
+        if (ret)
+                return ret;
+
+        return ret;
+}
+
 int btrfs_error_unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
 {
         return unpin_extent_range(root, start, end);