bcachefs: trans->notrace_relock_fail

When we unlock in order to submit IO, the next relock event is likely to
fail if submit_bio() blocked - we shouldn't those events in our _fail
stats, since those are expected events and shouldn't cause test
failures.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -2854,8 +2854,10 @@ u32 bch2_trans_begin(struct btree_trans *trans)
 		bch2_trans_reset_srcu_lock(trans);
 
 	trans->last_restarted_ip = _RET_IP_;
-	if (trans->restarted)
+	if (trans->restarted) {
 		bch2_btree_path_traverse_all(trans);
+		trans->notrace_relock_fail = false;
+	}
 
 	trans->last_begin_time = local_clock();
 	return trans->restart_count;

fs/bcachefs/btree_locking.c

@@ -473,7 +473,7 @@ bool __bch2_btree_node_relock(struct btree_trans *trans,
 		return true;
 	}
 fail:
-	if (trace)
+	if (trace && !trans->notrace_relock_fail)
 		trace_and_count(trans->c, btree_path_relock_fail, trans, _RET_IP_, path, level);
 	return false;
 }

fs/bcachefs/btree_types.h

@@ -425,6 +425,7 @@ struct btree_trans {
 	bool			memory_allocation_failure:1;
 	bool			journal_transaction_names:1;
 	bool			journal_replay_not_finished:1;
+	bool			notrace_relock_fail:1;
 	enum bch_errcode	restarted:16;
 	u32			restart_count;
 	unsigned long		last_restarted_ip;

fs/bcachefs/io.c

@@ -2375,6 +2375,12 @@ int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,
 			else
 				submit_bio_wait(&rbio->bio);
 		}
+
+		/*
+		 * We just submitted IO which may block, we expect relock fail
+		 * events and shouldn't count them:
+		 */
+		trans->notrace_relock_fail = true;
 	} else {
 		/* Attempting reconstruct read: */
 		if (bch2_ec_read_extent(c, rbio)) {