bcachefs: Fix btree_trans list ordering

The debug code relies on btree_trans_list being ordered so that it can
resume on subsequent calls or lock restarts.

However, it was using trans->locknig_wait.task.pid, which is incorrect
since btree_trans objects are cached and reused - typically by different
tasks.

Fix this by switching to pointer order, and also sort them lazily when
required - speeding up the btree_trans_get() fastpath.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 2 insertions, 7 deletions

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 15c1c7cfefe6..0ed9e6574fcd 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -3149,15 +3149,10 @@ struct btree_trans *__bch2_trans_get(struct bch_fs *c, unsigned fn_idx)
 			BUG_ON(pos_task &&
 			       pid == pos_task->pid &&
 			       pos->locked);
-
-			if (pos_task && pid < pos_task->pid) {
-				list_add_tail(&trans->list, &pos->list);
-				goto list_add_done;
-			}
 		}
 	}
-	list_add_tail(&trans->list, &c->btree_trans_list);
-list_add_done:
+
+	list_add(&trans->list, &c->btree_trans_list);
 	seqmutex_unlock(&c->btree_trans_lock);
 got_trans:
 	trans->c		= c;