mm: memcg: remove unneeded checks from newpage_charge()

All callsites pass in freshly allocated pages and a valid mm.  As a
result, all checks pertaining to the page's mapcount, page->mapping or the
fallback to init_mm are unneeded.

Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 12 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a63ad141083c..2450d89486d4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2748,19 +2748,11 @@ int mem_cgroup_newpage_charge(struct page *page,
 {
         if (mem_cgroup_disabled())
                 return 0;
-        /*
-         * If already mapped, we don't have to account.
-         * If page cache, page->mapping has address_space.
-         * But page->mapping may have out-of-use anon_vma pointer,
-         * detecit it by PageAnon() check. newly-mapped-anon's page->mapping
-         * is NULL.
-         */
-        if (page_mapped(page) || (page->mapping && !PageAnon(page)))
-                return 0;
-        if (unlikely(!mm))
-                mm = &init_mm;
+        VM_BUG_ON(page_mapped(page));
+        VM_BUG_ON(page->mapping && !PageAnon(page));
+        VM_BUG_ON(!mm);
         return mem_cgroup_charge_common(page, mm, gfp_mask,
-                                MEM_CGROUP_CHARGE_TYPE_MAPPED);
+                                        MEM_CGROUP_CHARGE_TYPE_MAPPED);
 }
 
 static void