bcachefs: Fix for running in degraded mode

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

fs/bcachefs/journal_io.c

@@ -1036,7 +1036,7 @@ static int journal_write_alloc(struct journal *j, struct journal_buf *w,
 	spin_unlock(&j->lock);
 	rcu_read_unlock();
 
-	return replicas >= replicas_want ? 0 : -EROFS;
+	return replicas >= c->opts.metadata_replicas_required ? 0 : -EROFS;
 }
 
 static void journal_write_compact(struct jset *jset)