linux-kernel - Re: [PATCH] diskquota: 32bit quota tools on 64bit architectures

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Message-Id: <200610251303.50551.arnd@arndb.de>
Date:	Wed, 25 Oct 2006 13:03:48 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Vasily Tarasov <vtaras@...nvz.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, Jan Kara <jack@...e.cz>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Roman Kagan <rkagan@...ru>,
	Randy Dunlap <rdunlap@...otime.net>,
	Dmitry Mishin <dim@...nvz.org>, Andi Kleen <ak@...e.de>,
	Vasily Averin <vvs@...ru>,
	Christoph Hellwig <hch@...radead.org>,
	Kirill Korotaev <dev@...nvz.org>,
	OpenVZ Developers List <devel@...nvz.org>
Subject: Re: [PATCH] diskquota: 32bit quota tools on 64bit architectures

On Wednesday 25 October 2006 12:03, Vasily Tarasov wrote:
> + * This code works only for 32 bit quota tools over 64 bit OS (x86_64, ia64)
> + * and is necessary due to alignment problems.
> + */
> +struct compat_if_dqblk {
> +       compat_uint_t dqb_bhardlimit[2];
> +       compat_uint_t dqb_bsoftlimit[2];
> +       compat_uint_t dqb_curspace[2];
> +       compat_uint_t dqb_ihardlimit[2];
> +       compat_uint_t dqb_isoftlimit[2];
> +       compat_uint_t dqb_curinodes[2];
> +       compat_uint_t dqb_btime[2];
> +       compat_uint_t dqb_itime[2];
> +       compat_uint_t dqb_valid;
> +};
> +
> +/* XFS structures */
> +struct compat_fs_qfilestat {
> +       compat_uint_t dqb_bhardlimit[2];
> +       compat_uint_t   qfs_nblks[2];
> +       compat_uint_t   qfs_nextents;
> +};
> +

The patch looks technically correct, but you have defined the structures
in a somewhat unusual way. I'd have defined them with 
attribute((packed, aligned(4))) in the end.

Or even better, we should probably add a 

typedef unsigned long long __attribute__((aligned(4))) compat_u64;

for x86 compat and use that instead of compat_uint_t foo[2].

	Arnd <><
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