Btrfs: allocator improvements, inode block groups

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 43a4f1d..6b50076 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -3,6 +3,7 @@
 
 struct btrfs_inode {
 	struct btrfs_root *root;
+	struct btrfs_block_group_cache *block_group;
 	struct btrfs_key location;
 	struct inode vfs_inode;
 };