On Fri, 4 Feb 2011 10:26:50 +0100 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > On Fri, Feb 04, 2011 at 09:01:45AM +0900, KAMEZAWA Hiroyuki wrote: > > On Thu, 3 Feb 2011 15:26:02 +0100 > > Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > > > All callsites check PCG_USED before passing pc->mem_cgroup, so the > > > latter is never NULL. > > > > > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > > > Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > Thank you! > > > I want BUG_ON() here. > > I thought about it too at first. But look at the callsites, all but > one of them do not even expect this function to return NULL, so if > this condition had ever been true, we would have seen crashes in the > callsites. > Hmm ok. -Kame > The only caller that checks for NULL is > mem_cgroup_get_reclaim_stat_from_page() and I propose to remove that > as well; patch attached. > > Do you insist on the BUG_ON? > > --- > Subject: memcg: page_cgroup_zoneinfo never returns NULL > > For a page charged to a memcg, there is always valid memcg per-zone > info. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > --- > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 4a4483d..5f974b3 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1017,9 +1017,6 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page) > /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */ > smp_rmb(); > mz = page_cgroup_zoneinfo(pc->mem_cgroup, page); > - if (!mz) > - return NULL; > - > return &mz->reclaim_stat; > } > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>