bcachefs: btree_update_nodes_written() requires alloc reserve

Also, in the btree_update_start() path, if we already have a journal
pre-reservation we don't want to take another - that's a deadlock.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_update_interior.c

@@ -529,6 +529,8 @@ static void btree_update_nodes_written(struct btree_update *as)
 	 */
 	ret = bch2_trans_do(c, &as->disk_res, &journal_seq,
 			    BTREE_INSERT_NOFAIL|
+			    BTREE_INSERT_USE_RESERVE|
+			    BTREE_INSERT_USE_ALLOC_RESERVE|
 			    BTREE_INSERT_NOCHECK_RW|
 			    BTREE_INSERT_JOURNAL_RESERVED,
 			    btree_update_nodes_written_trans(&trans, as));
@@ -886,6 +888,7 @@ bch2_btree_update_start(struct btree_trans *trans, enum btree_id id,
 	bch2_keylist_init(&as->new_keys, as->_new_keys);
 	bch2_keylist_init(&as->parent_keys, as->inline_keys);
 
+	if (!(flags & BTREE_INSERT_JOURNAL_RESERVED))
 		ret = bch2_journal_preres_get(&c->journal, &as->journal_preres,
 					      BTREE_UPDATE_JOURNAL_RES,
 					      JOURNAL_RES_GET_NONBLOCK);