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>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index f56c818e56bc3b118cfc9d1b70b6c83c01609999..ad800e62cb7a603fdd5f7fb1a752edb03417dbb4 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -305,11 +305,9 @@ struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
 struct lruvec *mem_cgroup_page_lruvec(struct page *, struct zone *);
 
 bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);
-
-struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
-
 struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
+
 static inline
 struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css){
        return css ? container_of(css, struct mem_cgroup, css) : NULL;
@@ -556,11 +554,6 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
        return &zone->lruvec;
 }
 
-static inline struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
-{
-       return NULL;
-}
-
 static inline bool mm_match_cgroup(struct mm_struct *mm,
                struct mem_cgroup *memcg)
 {

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 01009726d4120fff4ff47072c8d69df44524eb2e..6ddaeba34e097a7553d33b8add26e26a27d3c81a 100644 (file)
--- 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);