bcachefs: Don't do extent merging before journal replay is finished

We don't normally do extent updates this early in recovery, but some of
the repair paths have to and when we do, we don't want to do anything
that requires the snapshots table.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_update.c

@@ -38,6 +38,9 @@ static noinline int extent_front_merge(struct btree_trans *trans,
 	struct bkey_i *update;
 	int ret;
 
+	if (unlikely(trans->journal_replay_not_finished))
+		return 0;
+
 	update = bch2_bkey_make_mut_noupdate(trans, k);
 	ret = PTR_ERR_OR_ZERO(update);
 	if (ret)
@@ -69,6 +72,9 @@ static noinline int extent_back_merge(struct btree_trans *trans,
 	struct bch_fs *c = trans->c;
 	int ret;
 
+	if (unlikely(trans->journal_replay_not_finished))
+		return 0;
+
 	ret =   bch2_key_has_snapshot_overwrites(trans, iter->btree_id, insert->k.p) ?:
 		bch2_key_has_snapshot_overwrites(trans, iter->btree_id, k.k->p);
 	if (ret < 0)