map $uri $blogname{
    ~^(?P<blogpath>/[^/]+/)files/(.*)       $blogpath ;
}

map $blogname $blogid{
    default -999;

    #Ref: http://wordpress.org/extend/plugins/nginx-helper/
    #include /var/www/wordpress/wp-content/plugins/nginx-helper/map.conf ;
}

server {
    server_name example.com ;

    root /var/www/example.com/htdocs;
    index index.php;

    location ~ ^(/[^/]+/)?files/(.+) {
        try_files /wp-content/blogs.dir/$blogid/files/$2 /wp-includes/ms-files.php?file=$2 ;
        access_log off;     log_not_found off; expires max;
    }

    #avoid php readfile()
    location ^~ /blogs.dir {
        internal;
        alias /var/www/example.com/htdocs/wp-content/blogs.dir ;
        access_log off;     log_not_found off; expires max;
    }

    if (!-e $request_filename) {
        rewrite /wp-admin$ $scheme://$host$uri/ permanent;
        rewrite ^(/[^/]+)?(/wp-.*) $2 last;
        rewrite ^(/[^/]+)?(/.*\.php) $2 last;
    }

    location / {
        try_files $uri $uri/ /index.php?$args ;
    }

    location ~ \.php$ {
        try_files $uri =404;
        include fastcgi_params;
        fastcgi_pass php;
    }

    #add some rules for static content expiry-headers here
}
