memcg: remove NULL check from lookup_page_cgroup() result

The page_cgroup array is set up before even fork is initialized.  I
seriously doubt that this code executes before the array is alloc'd.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 4 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b94cd24c5baa..3a2d54bdf076 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2369,10 +2369,7 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
         }
 
         pc = lookup_page_cgroup(page);
-        /* can happen at boot */
-        if (unlikely(!pc))
-                return 0;
-        prefetchw(pc);
+        BUG_ON(!pc); /* XXX: remove this and move pc lookup into commit */
 
         ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, oom, page_size);
         if (ret || !mem)