From: Arnd Bergmann <arnd@arndb.de>
To: Namhyung Kim <namhyung@gmail.com>
Subject: Re: [PATCH] init/do_mounts.c: replace sys_mount() to do_mount()
Date: Tue, 17 Aug 2010 15:15:26 +0200
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Cc: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>, linux-kernel@vger.kernel.org
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On Tuesday 17 August 2010, Namhyung Kim wrote:
>  static int __init do_mount_root(char *name, char *fs, int flags, void *data)
>  {
> -       int err = sys_mount(name, "/root", fs, flags, data);
> +       int err;
> +       unsigned long data_page = 0;
> +
> +       if (data) {
> +               /* data should be in a page */
> +               data_page = __get_free_page(GFP_KERNEL);
> +               if (!data_page)
> +                       return -ENOMEM;
> +               strlcpy((char *) data_page, data, PAGE_SIZE);
> +       }
> +
> +       err = do_mount(name, "/root", fs, flags, (void *) data_page);
> +
> +       if (data_page)
> +               free_page(data_page);

AFAICT there is no need for the copy at all here. The reason that sys_mount
copies to a separate page is that it gets passed an arbitrary-length user
input.

	Arnd
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