mm/memcg: avoid page count check for zone device

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.

[mhocko@suse.com: nano-optimize VM_BUG_ON in uncharge_page]
Link: http://lkml.kernel.org/r/20170914190011.5217-1-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Evgeny Baskakov <ebaskakov@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 696c652..d5f3a62 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5658,7 +5658,8 @@ 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(page_count(page) && !is_zone_device_page(page) &&
+                       !PageHWPoison(page) , page);
 
        if (!page->mem_cgroup)
                return;