On Thu 14-09-17 15:00:11, [email protected] wrote: > From: Jérôme Glisse <[email protected]> > > 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 <[email protected]> > Reported-by: Evgeny Baskakov <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Johannes Weiner <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Vladimir Davydov <[email protected]>
Acked-by: Michal Hocko <[email protected]> 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
