bcachefs: Assert that we don't lock nodes when !trans->locked

We rely on the trans->locked to know if a trans has nodes locked for
assertions about deadlocks; there can't be more than one trans in the
same process that is locked.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_locking.h

@@ -218,14 +218,12 @@ static inline int __btree_node_lock_nopath(struct btree_trans *trans,
 					 bool lock_may_not_fail,
 					 unsigned long ip)
 {
-	int ret;
-
 	trans->lock_may_not_fail = lock_may_not_fail;
 	trans->lock_must_abort	= false;
 	trans->locking		= b;
 
-	ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
-				 bch2_six_check_for_deadlock, trans, ip);
+	int ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
+				     bch2_six_check_for_deadlock, trans, ip);
 	WRITE_ONCE(trans->locking, NULL);
 	WRITE_ONCE(trans->locking_wait.start_time, 0);
 
@@ -284,6 +282,7 @@ static inline int btree_node_lock(struct btree_trans *trans,
 	int ret = 0;
 
 	EBUG_ON(level >= BTREE_MAX_DEPTH);
+	bch2_trans_verify_not_unlocked(trans);
 
 	if (likely(six_trylock_type(&b->lock, type)) ||
 	    btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) ||

fs/bcachefs/btree_update_interior.c

@@ -731,6 +731,18 @@ 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:
+	/*
+	 * Ensure transaction is unlocked before using btree_node_lock_nopath()
+	 * (the use of which is always suspect, we need to work on removing this
+	 * in the future)
+	 *
+	 * It should be, but bch2_path_get_unlocked_mut() -> bch2_path_get()
+	 * calls bch2_path_upgrade(), before we call path_make_mut(), so we may
+	 * rarely end up with a locked path besides the one we have here:
+	 */
+	bch2_trans_unlock(trans);
+	bch2_trans_begin(trans);
+
 	/*
 	 * 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
@@ -750,18 +762,6 @@ static void btree_update_nodes_written(struct btree_update *as)
 		 * we're in journal error state:
 		 */
 
-		/*
-		 * Ensure transaction is unlocked before using
-		 * btree_node_lock_nopath() (the use of which is always suspect,
-		 * we need to work on removing this in the future)
-		 *
-		 * It should be, but bch2_path_get_unlocked_mut() -> bch2_path_get()
-		 * calls bch2_path_upgrade(), before we call path_make_mut(), so
-		 * we may rarely end up with a locked path besides the one we
-		 * have here:
-		 */
-		bch2_trans_unlock(trans);
-		bch2_trans_begin(trans);
 		btree_path_idx_t path_idx = bch2_path_get_unlocked_mut(trans,
 						as->btree_id, b->c.level, b->key.k.p);
 		struct btree_path *path = trans->paths + path_idx;

fs/bcachefs/btree_update_interior.h

@@ -159,6 +159,8 @@ static inline int bch2_foreground_maybe_merge(struct btree_trans *trans,
 					      unsigned level,
 					      unsigned flags)
 {
+	bch2_trans_verify_not_unlocked(trans);
+
 	return  bch2_foreground_maybe_merge_sibling(trans, path, level, flags,
 						    btree_prev_sib) ?:
 		bch2_foreground_maybe_merge_sibling(trans, path, level, flags,