[PATCH -mm v7 3/6] memcg: zap try_get_mem_cgroup_from_page

Vladimir Davydov
2015-07-11T14:48:47Z

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

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
---
include/linux/memcontrol.h | 6 ------
mm/memcontrol.c | 48 ++++++++++++----------------------------------
2 files changed, 12 insertions(+), 42 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 50069abebc3c..635edfe06bac 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -94,7 +94,6 @@ bool mem_cgroup_is_descendant(struct mem_cgroup *memcg,
struct mem_cgroup *root);
bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);

-extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);

extern struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
@@ -259,11 +258,6 @@ 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 894dc2169979..fa1447fcba33 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2378,40 +2378,6 @@ 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);
@@ -5628,8 +5594,20 @@ 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)) {
@@ -5637,8 +5615,6 @@ 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);

--
2.1.4