Re: [PATCH 1/6] memcg: replace unsigned long by u64 to avoid overflow

[Kamezawa Hiroyuki]

(2012/06/23 18:26), Johannes Weiner wrote:
> On Sat, Jun 23, 2012 at 05:03:39PM +0800, Wanpeng Li wrote:
> > On Sat, Jun 23, 2012 at 10:15:14AM +0200, Johannes Weiner wrote:
> > > On Sat, Jun 23, 2012 at 02:15:34PM +0800, Wanpeng Li wrote:
> > > > From: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
> > > >
> > > > Since the return value variable in mem_cgroup_zone_nr_lru_pages and
> > > > mem_cgroup_node_nr_lru_pages functions are u64, so replace the return
> > > > value of funtions by u64 to avoid overflow.
> > >
> > > I wonder what 16 TB of memory must think running on a 32-bit kernel...
> > > "What is this, an address space for ants?"
> >
> > Hi Johannes,
> >
> > You mean change all u64 in memcg to unsigned long? or something I
> > miss....
>
> Not _all_ of them, we have some that count bytes.  But those counting
> pages should probably be ulong, yes.
>
> I think Kame added the ones that you wanted to adjust the surroundings
> for in particular, so let's ask him.  Kame?

I've been using 'unsigned long' for the number of pages and 'u64' for the number of
bytes. I think it's enough and it should be. I don't have any reason to use u64 for
the number of pages on 32bit archs.
If 'bytes' are handled by 'unsigned long', please fix it.

BTW, zone_page_state()::/include/linux/vmstat.h returns 'unsigned long'.
If you want to change this in memcg, please change zone's ones first.

Thanks,
-Kame

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