bcachefs: Fix use after free in bch2_check_fix_ptrs()

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

fs/bcachefs/btree_gc.c

@@ -691,12 +691,6 @@ static int bch2_check_fix_ptrs(struct btree_trans *trans, enum btree_id btree_id
 			}
 		}
 
-		ret = bch2_journal_key_insert_take(c, btree_id, level, new);
-		if (ret) {
-			kfree(new);
-			goto err;
-		}
-
 		if (level)
 			bch2_btree_node_update_key_early(trans, btree_id, level - 1, *k, new);
 
@@ -710,6 +704,12 @@ static int bch2_check_fix_ptrs(struct btree_trans *trans, enum btree_id btree_id
 			bch_info(c, "new key %s", buf.buf);
 		}
 
+		ret = bch2_journal_key_insert_take(c, btree_id, level, new);
+		if (ret) {
+			kfree(new);
+			goto err;
+		}
+
 		*k = bkey_i_to_s_c(new);
 	}
 err: