bcachefs: Don't corrupt journal keys gap buffer when dropping alloc info

Signed-off-by: Kent Overstreet <[e-mail]>

fs/bcachefs/btree_io.c

···
 	if (saw_error && !btree_node_read_error(b)) {
 		printbuf_reset(&buf);
 		bch2_bpos_to_text(&buf, b->key.k.p);
-		bch_info(c, "%s: rewriting btree node at btree=%s level=%u %s due to error",
+		bch_err_ratelimited(c, "%s: rewriting btree node at btree=%s level=%u %s due to error",
 			 __func__, bch2_btree_id_str(b->c.btree_id), b->c.level, buf.buf);
 
 		bch2_btree_node_rewrite_async(c, b);

fs/bcachefs/recovery.c

···
 	struct journal_keys *keys = &c->journal_keys;
 	size_t src, dst;
 
+	move_gap(keys, keys->nr);
+
 	for (src = 0, dst = 0; src < keys->nr; src++)
 		if (!btree_id_is_alloc(keys->data[src].btree_id))
 			keys->data[dst++] = keys->data[src];
-	keys->nr = dst;
+	keys->nr = keys->gap = dst;
 }
 
 /*
···
 	}
 
 	BUG_ON(!atomic_read(&keys->ref));
+
+	move_gap(keys, keys->nr);
 
 	/*
 	 * First, attempt to replay keys in sorted order. This is more

fs/bcachefs/util.h

···
 /* Move the gap in a gap buffer: */
 #define move_gap(_d, _new_gap)						\
 do {									\
+	BUG_ON(_new_gap > (_d)->nr);					\
+	BUG_ON((_d)->gap > (_d)->nr);					\
+									\
 	__move_gap((_d)->data, sizeof((_d)->data[0]),			\
 		   (_d)->nr, (_d)->size, (_d)->gap, _new_gap);		\
 	(_d)->gap = _new_gap;						\