memcg: zap try_get_mem_cgroup_from_page

It is only used in mem_cgroup_try_charge, so fold it in and zap it.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 36 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 01009726d412..6ddaeba34e09 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2099,40 +2099,6 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
         css_put_many(&memcg->css, nr_pages);
 }
 
-/*
- * try_get_mem_cgroup_from_page - look up page's memcg association
- * @page: the page
- *
- * Look up, get a css reference, and return the memcg that owns @page.
- *
- * The page must be locked to prevent racing with swap-in and page
- * cache charges.  If coming from an unlocked page table, the caller
- * must ensure the page is on the LRU or this can race with charging.
- */
-struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
-{
-        struct mem_cgroup *memcg;
-        unsigned short id;
-        swp_entry_t ent;
-
-        VM_BUG_ON_PAGE(!PageLocked(page), page);
-
-        memcg = page->mem_cgroup;
-        if (memcg) {
-                if (!css_tryget_online(&memcg->css))
-                        memcg = NULL;
-        } else if (PageSwapCache(page)) {
-                ent.val = page_private(page);
-                id = lookup_swap_cgroup_id(ent);
-                rcu_read_lock();
-                memcg = mem_cgroup_from_id(id);
-                if (memcg && !css_tryget_online(&memcg->css))
-                        memcg = NULL;
-                rcu_read_unlock();
-        }
-        return memcg;
-}
-
 static void lock_page_lru(struct page *page, int *isolated)
 {
         struct zone *zone = page_zone(page);
@@ -5329,8 +5295,20 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
                  * the page lock, which serializes swap cache removal, which
                  * in turn serializes uncharging.
                  */
+                VM_BUG_ON_PAGE(!PageLocked(page), page);
                 if (page->mem_cgroup)
                         goto out;
+
+                if (do_swap_account) {
+                        swp_entry_t ent = { .val = page_private(page), };
+                        unsigned short id = lookup_swap_cgroup_id(ent);
+
+                        rcu_read_lock();
+                        memcg = mem_cgroup_from_id(id);
+                        if (memcg && !css_tryget_online(&memcg->css))
+                                memcg = NULL;
+                        rcu_read_unlock();
+                }
         }
 
         if (PageTransHuge(page)) {
@@ -5338,8 +5316,6 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
                 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
         }
 
-        if (do_swap_account && PageSwapCache(page))
-                memcg = try_get_mem_cgroup_from_page(page);
         if (!memcg)
                 memcg = get_mem_cgroup_from_mm(mm);