memcg: rename and export try_get_mem_cgroup_from_page()

So that the hwpoison injector can get mem_cgroup for arbitrary page
and thus know whether it is owned by some mem_cgroup task(s).

[AK: Merged with latest git tree]

CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Hugh Dickins <hugh.dickins@tiscali.co.uk>
CC: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
CC: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index bf9213b2db8f2da2a443d8788d2d70eb0a003af8..fc9bae82ac425247313a133c37a4d3867f2fe183 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -68,6 +68,7 @@ extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 extern void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask);
 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
 
+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);
 
 static inline
@@ -189,6 +190,11 @@ mem_cgroup_move_lists(struct page *page, enum lru_list from, enum lru_list to)
 {
 }
 
+static inline struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
+{
+       return NULL;
+}
+
 static inline int mm_match_cgroup(struct mm_struct *mm, struct mem_cgroup *mem)
 {
        return 1;

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e0c2066495e3fd4adf19254266df619048546cdb..b5ac61ce73461531bd29a455d768ca26885a3d42 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1379,25 +1379,22 @@ static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
        return container_of(css, struct mem_cgroup, css);
 }
 
-static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
+struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
 {
-       struct mem_cgroup *mem;
+       struct mem_cgroup *mem = NULL;
        struct page_cgroup *pc;
        unsigned short id;
        swp_entry_t ent;
 
        VM_BUG_ON(!PageLocked(page));
 
-       if (!PageSwapCache(page))
-               return NULL;
-
        pc = lookup_page_cgroup(page);
        lock_page_cgroup(pc);
        if (PageCgroupUsed(pc)) {
                mem = pc->mem_cgroup;
                if (mem && !css_tryget(&mem->css))
                        mem = NULL;
-       } else {
+       } else if (PageSwapCache(page)) {
                ent.val = page_private(page);
                id = lookup_swap_cgroup(ent);
                rcu_read_lock();
@@ -1743,7 +1740,7 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
         */
        if (!PageSwapCache(page))
                goto charge_cur_mm;
-       mem = try_get_mem_cgroup_from_swapcache(page);
+       mem = try_get_mem_cgroup_from_page(page);
        if (!mem)
                goto charge_cur_mm;
        *ptr = mem;