Commit 1f88c356 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Fix a KMSAN splat in btree_update_nodes_written() 



We may sometimes read from uninitialized memory; we know, and that's ok.

We check if a btree node has been reused before waiting on any
outstanding IO.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 28aa859b

fs/bcachefs/btree_update_interior.c

+9 −9
Original line number Diff line number Diff line
@@ -649,6 +649,14 @@ static int btree_update_nodes_written_trans(struct btree_trans *trans, 
	return 0;

}



/* If the node has been reused, we might be reading uninitialized memory - that's fine: */

static noinline __no_kmsan_checks bool btree_node_seq_matches(struct btree *b, __le64 seq)

{

	struct btree_node *b_data = READ_ONCE(b->data);



	return (b_data ? b_data->keys.seq : 0) == seq;

}



static void btree_update_nodes_written(struct btree_update *as)

{

	struct bch_fs *c = as->c;
@@ -677,17 +685,9 @@ static void btree_update_nodes_written(struct btree_update *as) 
	 * on disk:

	 */

	for (i = 0; i < as->nr_old_nodes; i++) {

		__le64 seq;



		b = as->old_nodes[i];



		bch2_trans_begin(trans);

		btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_read);

		seq = b->data ? b->data->keys.seq : 0;

		six_unlock_read(&b->c.lock);

		bch2_trans_unlock_long(trans);



		if (seq == as->old_nodes_seq[i])

		if (btree_node_seq_matches(b, as->old_nodes_seq[i]))

			wait_on_bit_io(&b->flags, BTREE_NODE_write_in_flight_inner,

				       TASK_UNINTERRUPTIBLE);

	}