bcachefs: Fix bch2_mark_update()

When the old or new key doesn't exist, we should still pass in a deleted
key with the correct pos. This fixes a bug in the ec code, when
bch2_mark_stripe() was looking up the wrong in-memory stripe.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/buckets.c

@@ -1231,6 +1231,8 @@ int bch2_mark_key(struct bch_fs *c, struct bkey_s_c new, unsigned flags)
 	struct bkey_s_c old = (struct bkey_s_c) { &deleted, NULL };
 	int ret;
 
+	deleted.p = new.k->p;
+
 	percpu_down_read(&c->mark_lock);
 	ret = bch2_mark_key_locked(c, old, new, 0, flags);
 	percpu_up_read(&c->mark_lock);
@@ -1248,6 +1250,8 @@ int bch2_mark_update(struct btree_trans *trans, struct btree_path *path,
 	struct bkey		unpacked;
 	int ret;
 
+	_deleted.p = path->pos;
+
 	if (unlikely(flags & BTREE_TRIGGER_NORUN))
 		return 0;
 
@@ -1846,6 +1850,8 @@ int bch2_trans_mark_update(struct btree_trans *trans,
 	struct bkey		unpacked;
 	int ret;
 
+	_deleted.p = path->pos;
+
 	if (unlikely(flags & BTREE_TRIGGER_NORUN))
 		return 0;