rewriteのログものせておきます。

-- PassengerEnabled off の場合（rewriteが走っている）
(3) [perdir /var/www/hoge/public/] applying pattern '^$' to uri ''
(2) [perdir /var/www/hoge/public/] rewrite '' -> '/m/'
(2) [perdir /var/www/hoge/public/] explicitly forcing redirect with http://hoge.hoge.com/m/
(1) [perdir /var/www/hoge/public/] escaping http://hoge.hoge.com/m/ for redirect
(1) [perdir /var/www/hoge/public/] redirect to http://hoge.hoge.com/m/ [REDIRECT/302]

-- PassengerEnabled on の場合（rewriteが走っていない）
(3) [perdir /var/www/hoge/public/] strip per-dir prefix: /var/www/hoge/public/index.html -> index.html
(3) [perdir /var/www/hoge/public/] applying pattern '^$' to uri 'index.html'
(1) [perdir /var/www/hoge/public/] pass through /var/www/hoge/public/index.html