Andrew Morton writes:
> On Mon, 18 Jun 2007 12:21:47 +0400
> Vasily Tarasov <[email protected]> wrote:
>
> > From: Vasily Tarasov <[email protected]>
> >
> > This patch should be applied after Arnd Bergmann's patch,
> > that intoduces new compat types:
> > http://lkml.org/lkml/2007/6/15/98
> >
> > OpenVZ Linux kernel team has discovered the problem
> > with 32bit quota tools working on 64bit architectures.
> > In 2.6.10 kernel sys32_quotactl() function was replaced by sys_quotactl() with
> > the comment "sys_quotactl seems to be 32/64bit clean, enable it for 32bit"
> > However this isn't right. Look at if_dqblk structure:
> >
> > struct if_dqblk {
> > __u64 dqb_bhardlimit;
> > __u64 dqb_bsoftlimit;
> > __u64 dqb_curspace;
> > __u64 dqb_ihardlimit;
> > __u64 dqb_isoftlimit;
> > __u64 dqb_curinodes;
> > __u64 dqb_btime;
> > __u64 dqb_itime;
> > __u32 dqb_valid;
> > };
> >
> > For 32 bit quota tools sizeof(if_dqblk) == 0x44.
> > But for 64 bit kernel its size is 0x48, 'cause of alignment!
> > Thus we got a problem. Attached patch reintroduce sys32_quotactl() function,
> > that handles this and related situations.
> >
> > Signed-off-by: Vasily Tarasov <[email protected]>
> >
> > ---
> >
> > In OpenVZ technology 32 bit Virtual Environments over
> > 64 bit OS are common, hence we have customers, that complains on this bad quota
> > behaviour:
> >
> > # /usr/bin/quota
> > quota: error while getting quota from /dev/sda1 for 0: Success
> >
> > The reason is caused above.
>
> Only x86_64 and ia64 are fixed. Would it be correct to assume that the
> other CONFIG_COMPAT architectures also need to be fixed?
I complained about this very issue when a previous version of
this patch was submitted last week, and Arnd explained that
non-x86 doesn't have a problem here because alignof(u64) is the
same in 32- and 64-bit modes.
However, the fact that the patch description talks about 32-
and 64-bit machines _in_general_, while the patch clearly only
handles x86-32 on x86-64 and ia64, is itself a bug. A more
precise patch description and a better comment in the code
is in order, I think.
/Mikael
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