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

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Date:	Mon, 23 Oct 2006 14:51:31 +0400
From:	Vasily Tarasov <vtaras@...nvz.org>
To:	Arnd Bergmann <arnd@...db.de>
CC:	David Chinner <dgc@....com>
Subject: Re: [PATCH] diskquota: 32bit quota tools on 64bit architectures

Hello,

Arnd Bergmann wrote:

<snip>
> 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?
<snip>

The problem indeed exists:

ia32:
sizeof(fs_qfilestat) = 0x14
sizeof(fs_quota_stat) = 0x44

x86_64:
sizeof(fs_qfilestat) = 0x18
sizeof(fs_quota_stat) = 0x50

Note, that the difference between sizes of fs_qfilestat on ia32 and 
on x86_64 doesn't equal 8 bytes, as was expected (by me :)), but equals 12 bytes: 
'cause of padding at the end of fs_quota_stat structure on x86_64.

I will add support of 32-bit XFS quotactl over 64bit OS in next patch.

Thank you!
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