Commit beccf291 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Fix a race in btree_update_nodes_written() 



One btree update might have terminated in a node update, and then while
it is in flight another btree update might free that original node.

This race has to be handled in btree_update_nodes_written() - we were
missing a READ_ONCE().

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 9b31152f

fs/bcachefs/btree_update_interior.c

+7 −3
Original line number Diff line number Diff line
@@ -704,9 +704,13 @@ static void btree_update_nodes_written(struct btree_update *as) 
	bch2_fs_fatal_err_on(ret && !bch2_journal_error(&c->journal), c,

			     "%s", bch2_err_str(ret));

err:

	if (as->b) {



		b = as->b;

	/*

	 * We have to be careful because another thread might be getting ready

	 * to free as->b and calling btree_update_reparent() on us - we'll

	 * recheck under btree_update_lock below:

	 */

	b = READ_ONCE(as->b);

	if (b) {

		btree_path_idx_t path_idx = get_unlocked_mut_path(trans,

						as->btree_id, b->c.level, b->key.k.p);

		struct btree_path *path = trans->paths + path_idx;