bcachefs: better error message in btree_node_write_work()

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

fs/bcachefs/btree_io.c

@@ -1798,8 +1798,10 @@ static void btree_node_write_work(struct work_struct *work)
 	bch2_bkey_drop_ptrs(bkey_i_to_s(&wbio->key), ptr,
 		bch2_dev_list_has_dev(wbio->wbio.failed, ptr->dev));
 
-	if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(&wbio->key)))
+	if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(&wbio->key))) {
+		ret = -BCH_ERR_btree_write_all_failed;
 		goto err;
+	}
 
 	if (wbio->wbio.first_btree_write) {
 		if (wbio->wbio.failed.nr) {

fs/bcachefs/errcode.h

@@ -224,6 +224,7 @@
 	x(BCH_ERR_operation_blocked,    nocow_lock_blocked)			\
 	x(EIO,				btree_node_read_err)			\
 	x(EIO,				sb_not_downgraded)			\
+	x(EIO,				btree_write_all_failed)			\
 	x(BCH_ERR_btree_node_read_err,	btree_node_read_err_fixable)		\
 	x(BCH_ERR_btree_node_read_err,	btree_node_read_err_want_retry)		\
 	x(BCH_ERR_btree_node_read_err,	btree_node_read_err_must_retry)		\