bcachefs: Reconstruct missing snapshot nodes

When the snapshots btree is going, we'll have to delete huge amounts of
data - unless we can reconstruct it by looking at the keys that refer to
it.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
diff --git a/fs/bcachefs/bcachefs.h b/fs/bcachefs/bcachefs.h
index d1a0e54..a31a5f7 100644
--- a/fs/bcachefs/bcachefs.h
+++ b/fs/bcachefs/bcachefs.h
@@ -615,6 +615,7 @@ struct bch_dev {
  */
 
 #define BCH_FS_FLAGS()			\
+	x(new_fs)			\
 	x(started)			\
 	x(may_go_rw)			\
 	x(rw)				\