Messages in this thread | | | Date | Fri, 15 Sep 2017 09:01:00 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] mm/memcg: avoid page count check for zone device |
| |
On Thu 14-09-17 15:00:11, jglisse@redhat.com wrote: > From: Jérôme Glisse <jglisse@redhat.com> > > Fix for 4.14, zone device page always have an elevated refcount > of one and thus page count sanity check in uncharge_page() is > inappropriate for them. > > Signed-off-by: Jérôme Glisse <jglisse@redhat.com> > Reported-by: Evgeny Baskakov <ebaskakov@nvidia.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Side note. Wouldn't it be better to re-organize the check a bit? It is true that this is VM_BUG so it is not usually compiled in but when it preferably checks for unlikely cases first while the ref count will be 0 in the prevailing cases. So can we have VM_BUG_ON_PAGE(page_count(page) && !is_zone_device_page(page) && !PageHWPoison(page), page);
I would simply fold this nano optimization into the patch as you are touching it already. Not sure it is worth a separate commit.
> --- > mm/memcontrol.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 15af3da5af02..d51d3e1f49c9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5648,7 +5648,8 @@ static void uncharge_batch(const struct uncharge_gather *ug) > static void uncharge_page(struct page *page, struct uncharge_gather *ug) > { > VM_BUG_ON_PAGE(PageLRU(page), page); > - VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page); > + VM_BUG_ON_PAGE(!PageHWPoison(page) && !is_zone_device_page(page) && > + page_count(page), page); > > if (!page->mem_cgroup) > return; > -- > 2.13.5
-- Michal Hocko SUSE Labs
| |