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

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Date:	Sat, 21 Oct 2006 18:28:32 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Vasily Tarasov <vtaras@...nvz.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, Jan Kara <jack@...e.cz>,
	Dmitry Mishin <dim@...nvz.org>, Vasily Averin <vvs@...ru>,
	Kirill Korotaev <dev@...nvz.org>,
	OpenVZ Developers List <devel@...nvz.org>
Subject: Re: [PATCH] diskquota: 32bit quota tools on 64bit architectures

On Friday 20 October 2006 08:10, Vasily Tarasov wrote:
> Christoph Hellwig wrote:
>
> <snip>
>
> > Please allocate the structure using compat_alloc_userspace and copy
> > with copy_in_user instead of the set_fs trick.
>
> <snip>
>
> Good idea, thank you for your tip, I'll do it.

I think it would be even better to integrate this into fs/quota.c
and get rid of the extra copy entirely. The only thing you need
to do differently in case of 32 bit Q_GETQUOTA is the size
of the copy_{from,to}_user.

On a related topic, I just noticed 

typedef struct fs_qfilestat {
	__u64		qfs_ino;	/* inode number */
	__u64		qfs_nblks;	/* number of BBs 512-byte-blks */
	__u32		qfs_nextents;	/* number of extents */
} fs_qfilestat_t;

typedef struct fs_quota_stat {
	__s8		qs_version;	/* version number for future changes */
	__u16		qs_flags;	/* XFS_QUOTA_{U,P,G}DQ_{ACCT,ENFD} */
	__s8		qs_pad;		/* unused */
	fs_qfilestat_t	qs_uquota;	/* user quota storage information */
	fs_qfilestat_t	qs_gquota;	/* group quota storage information */
	__u32		qs_incoredqs;	/* number of dquots incore */
	__s32		qs_btimelimit;  /* limit for blks timer */	
	__s32		qs_itimelimit;  /* limit for inodes timer */	
	__s32		qs_rtbtimelimit;/* limit for rt blks timer */	
	__u16		qs_bwarnlimit;	/* limit for num warnings */
	__u16		qs_iwarnlimit;	/* limit for num warnings */
} fs_quota_stat_t;

This one seems to have a more severe problem in x86_64 compat
mode. I haven't tried it, but isn't everything down from
gs_gquota aligned differently on i386?

	Arnd <><
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