bcachefs: Fix packed bkey format calculation for new btree roots

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_gc.c

@@ -1311,6 +1311,9 @@ static void bch2_coalesce_nodes(struct bch_fs *c, struct btree_iter *iter,
 	/* Find a format that all keys in @old_nodes can pack into */
 	bch2_bkey_format_init(&format_state);
 
+	/*
+	 * XXX: this won't correctly take it account the new min/max keys:
+	 */
 	for (i = 0; i < nr_old_nodes; i++)
 		__bch2_btree_calc_format(&format_state, old_nodes[i]);
 

fs/bcachefs/btree_update_interior.c

@@ -82,8 +82,6 @@ void __bch2_btree_calc_format(struct bkey_format_state *s, struct btree *b)
 	struct bset_tree *t;
 	struct bkey uk;
 
-	bch2_bkey_format_add_pos(s, b->data->min_key);
-
 	for_each_bset(b, t)
 		bset_tree_for_each_key(b, t, k)
 			if (!bkey_deleted(k)) {
@@ -97,6 +95,8 @@ static struct bkey_format bch2_btree_calc_format(struct btree *b)
 	struct bkey_format_state s;
 
 	bch2_bkey_format_init(&s);
+	bch2_bkey_format_add_pos(&s, b->data->min_key);
+	bch2_bkey_format_add_pos(&s, b->data->max_key);
 	__bch2_btree_calc_format(&s, b);
 
 	return bch2_bkey_format_done(&s);
@@ -1578,8 +1578,10 @@ void __bch2_foreground_maybe_merge(struct bch_fs *c,
 	}
 
 	bch2_bkey_format_init(&new_s);
-	__bch2_btree_calc_format(&new_s, b);
-	__bch2_btree_calc_format(&new_s, m);
+	bch2_bkey_format_add_pos(&new_s, prev->data->min_key);
+	__bch2_btree_calc_format(&new_s, prev);
+	__bch2_btree_calc_format(&new_s, next);
+	bch2_bkey_format_add_pos(&new_s, next->data->max_key);
 	new_f = bch2_bkey_format_done(&new_s);
 
 	sib_u64s = btree_node_u64s_with_format(b, &new_f) +