bcachefs: btree_trans_restart_foreign_task()

In debug mode, we save the call stack on transaction restart - but
there's no locking, so we can't touch it if we're issuing the restart
from another thread.

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

Author: Kent Overstreet

fs/bcachefs/btree_iter.h

@@ -335,13 +335,20 @@ static inline void bch2_trans_verify_not_unlocked_or_in_restart(struct btree_tra
 }
 
 __always_inline
-static int btree_trans_restart_ip(struct btree_trans *trans, int err, unsigned long ip)
+static int btree_trans_restart_foreign_task(struct btree_trans *trans, int err, unsigned long ip)
 {
 	BUG_ON(err <= 0);
 	BUG_ON(!bch2_err_matches(-err, BCH_ERR_transaction_restart));
 
 	trans->restarted = err;
 	trans->last_restarted_ip = ip;
+	return -err;
+}
+
+__always_inline
+static int btree_trans_restart_ip(struct btree_trans *trans, int err, unsigned long ip)
+{
+	btree_trans_restart_foreign_task(trans, err, ip);
 #ifdef CONFIG_BCACHEFS_DEBUG
 	darray_exit(&trans->last_restarted_trace);
 	bch2_save_backtrace(&trans->last_restarted_trace, current, 0, GFP_NOWAIT);

fs/bcachefs/btree_locking.c

@@ -172,7 +172,9 @@ static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
 {
 	if (i == g->g) {
 		trace_would_deadlock(g, i->trans);
-		return btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
+		return btree_trans_restart_foreign_task(i->trans,
+					BCH_ERR_transaction_restart_would_deadlock,
+					_THIS_IP_);
 	} else {
 		i->trans->lock_must_abort = true;
 		wake_up_process(i->trans->locking_wait.task);