Commit 1841027c authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: bch2_gc_btree() should not use btree_root_lock 



btree_root_lock is for the root keys in btree_root, not the pointers to
the nodes themselves; this fixes a lock ordering issue between
btree_root_lock and btree node locks.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent f236ea4b

fs/bcachefs/btree_gc.c

+22 −8
Original line number Diff line number Diff line
@@ -641,16 +641,30 @@ static int bch2_gc_btree(struct btree_trans *trans, enum btree_id btree, bool in 
		target_depth = 0;



	/* root */

	mutex_lock(&c->btree_root_lock);

	struct btree *b = bch2_btree_id_root(c, btree)->b;

	if (!btree_node_fake(b)) {

	do {

retry_root:

		bch2_trans_begin(trans);



		struct btree_iter iter;

		bch2_trans_node_iter_init(trans, &iter, btree, POS_MIN,

					  0, bch2_btree_id_root(c, btree)->b->c.level, 0);

		struct btree *b = bch2_btree_iter_peek_node(&iter);

		ret = PTR_ERR_OR_ZERO(b);

		if (ret)

			goto err_root;



		if (b != btree_node_root(c, b)) {

			bch2_trans_iter_exit(trans, &iter);

			goto retry_root;

		}



		gc_pos_set(c, gc_pos_btree(btree, b->c.level + 1, SPOS_MAX));

		ret = lockrestart_do(trans,

			bch2_gc_mark_key(trans, b->c.btree_id, b->c.level + 1,

					 NULL, NULL, bkey_i_to_s_c(&b->key), initial));

		struct bkey_s_c k = bkey_i_to_s_c(&b->key);

		ret = bch2_gc_mark_key(trans, btree, b->c.level + 1, NULL, NULL, k, initial);

		level = b->c.level;

	}

	mutex_unlock(&c->btree_root_lock);

err_root:

		bch2_trans_iter_exit(trans, &iter);

	} while (bch2_err_matches(ret, BCH_ERR_transaction_restart));



	if (ret)

		return ret;