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, 6 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8ecc5419d8b6..b3fc8475870f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2065,6 +2065,12 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->metadata_alloc_profile = (u64)-1;
         fs_info->system_alloc_profile = fs_info->metadata_alloc_profile;
 
+        ret = btrfs_init_space_info(fs_info);
+        if (ret) {
+                printk(KERN_ERR "Failed to initial space info: %d\n", ret);
+                goto fail_block_groups;
+        }
+
         ret = btrfs_read_block_groups(extent_root);
         if (ret) {
                 printk(KERN_ERR "Failed to read block groups: %d\n", ret);