From: Bodo Eggert <7eggert@gmx.de>
Subject: Re: [PATCH 2/8] readahead: state based method routines: explicitly embed class_new/class_old inside flags
To: Fengguang Wu <wfg@mail.ustc.edu.cn>, Andrew Morton <akpm@osdl.org>,
       Martin Peschke <mp3@de.ibm.com>, linux-kernel@vger.kernel.org
Reply-To: 7eggert@gmx.de
Date: Sat, 27 Jan 2007 13:01:08 +0100
References: <7HR6P-3Wm-3@gated-at.bofh.it> <7HR6S-3Wm-13@gated-at.bofh.it>
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Fengguang Wu <wfg@mail.ustc.edu.cn> wrote:

> The new/old ra class were implicitly stored in low bits of
> file_ra_state.flags. Now make the data structure obvious, and remove the
> coding tricks.

> +++ linux-2.6.20-rc4-mm1/include/linux/fs.h

> -     unsigned long flags;    /* RA_FLAG_xxx | ra_class_old | ra_class_new */
> +     union {
> +             unsigned long   flags;  /* RA_FLAG_xxx | class_old | class_new */
> +             struct {
> +                     u8      class_new;
> +                     u8      class_old;

This doesn't work on big endiam machines, does it?

IMO you should use a bitfield instead.
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