Re: [PATCH 1/5 v2] memcg: replace unsigned long by u64 to avoid overflow

[Kamezawa Hiroyuki]

(2012/06/25 16:52), Johannes Weiner wrote:
> On Mon, Jun 25, 2012 at 02:04:20PM +0800, Wanpeng Li wrote:
> > Changlog:
> >
> > V2 -> V1:
> > * fix zone_page_state()::/include/linux/vmstat.h returns 'unsigned long'
> >
> > 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.
> >
> > Signed-off-by: Wanpeng Li <liwp.linux@xxxxxxxxx>
> > ---
> >   include/linux/vmstat.h |    2 +-
> >   mm/memcontrol.c        |    5 ++---
> >   2 files changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> > index 65efb92..6a14291 100644
> > --- a/include/linux/vmstat.h
> > +++ b/include/linux/vmstat.h
> > @@ -106,7 +106,7 @@ static inline unsigned long global_page_state(enum zone_stat_item item)
> >   	return x;
> >   }
> >
> > -static inline unsigned long zone_page_state(struct zone *zone,
> > +static inline u64 zone_page_state(struct zone *zone,
> >   					enum zone_stat_item item)
> >   {
> >   	long x = atomic_long_read(&zone->vm_stat[item]);
>
> We established that there is no known reason to use ulong for page
> counters and that IF YOU HAD ONE, you should obviously say so and then
> do a wholesale conversion.  But I don't think you have one.
>
> This patch makes absolutely no sense.
I agree. Then, Nack from me.

Thanks,
-Kame


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