bcachefs: Add a few tracepoints

Transaction restart tracing should probably be overhaulled at some
point.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_update_interior.c

@@ -1555,8 +1555,10 @@ int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
 	/* Hack, because gc and splitting nodes doesn't mix yet: */
 	if (!(flags & BTREE_INSERT_GC_LOCK_HELD) &&
 	    !down_read_trylock(&c->gc_lock)) {
-		if (flags & BTREE_INSERT_NOUNLOCK)
+		if (flags & BTREE_INSERT_NOUNLOCK) {
+			trace_transaction_restart_ip(trans->ip, _THIS_IP_);
 			return -EINTR;
+		}
 
 		bch2_trans_unlock(trans);
 		down_read(&c->gc_lock);
@@ -1584,6 +1586,8 @@ int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
 			BUG_ON(flags & BTREE_INSERT_NOUNLOCK);
 			bch2_trans_unlock(trans);
 			ret = -EINTR;
+
+			trace_transaction_restart_ip(trans->ip, _THIS_IP_);
 		}
 		goto out;
 	}

fs/bcachefs/trace.h

@@ -499,6 +499,23 @@ TRACE_EVENT(copygc,
 		__entry->buckets_moved, __entry->buckets_not_moved)
 );
 
+TRACE_EVENT(transaction_restart_ip,
+	TP_PROTO(unsigned long caller, unsigned long ip),
+	TP_ARGS(caller, ip),
+
+	TP_STRUCT__entry(
+		__field(unsigned long,		caller	)
+		__field(unsigned long,		ip	)
+	),
+
+	TP_fast_assign(
+		__entry->caller	= caller;
+		__entry->ip	= ip;
+	),
+
+	TP_printk("%pF %pF", (void *) __entry->caller, (void *) __entry->ip)
+);
+
 DECLARE_EVENT_CLASS(transaction_restart,
 	TP_PROTO(unsigned long ip),
 	TP_ARGS(ip),