memcg: fix mem_cgroup_shrink_usage()

Current mem_cgroup_shrink_usage() has two problems.

1. It doesn't call mem_cgroup_out_of_memory and doesn't update
   last_oom_jiffies, so pagefault_out_of_memory invokes global OOM.

2. Considering hierarchy, shrinking has to be done from the
   mem_over_limit, not from the memcg which the page would be charged to.

mem_cgroup_try_charge_swapin() does all of these things properly, so we
use it and call cancel_charge_swapin when it succeeded.

The name of "shrink_usage" is not appropriate for this behavior, so we
change it too.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.cn>
Cc: Paul Menage <menage@google.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 18 insertions, 23 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 575203ae2109..01c2d8f14685 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1617,37 +1617,28 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
 }
 
 /*
- * A call to try to shrink memory usage under specified resource controller.
- * This is typically used for page reclaiming for shmem for reducing side
- * effect of page allocation from shmem, which is used by some mem_cgroup.
+ * A call to try to shrink memory usage on charge failure at shmem's swapin.
+ * Calling hierarchical_reclaim is not enough because we should update
+ * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
+ * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
+ * not from the memcg which this page would be charged to.
+ * try_charge_swapin does all of these works properly.
  */
-int mem_cgroup_shrink_usage(struct page *page,
+int mem_cgroup_shmem_charge_fallback(struct page *page,
                             struct mm_struct *mm,
                             gfp_t gfp_mask)
 {
         struct mem_cgroup *mem = NULL;
-        int progress = 0;
-        int retry = MEM_CGROUP_RECLAIM_RETRIES;
+        int ret;
 
         if (mem_cgroup_disabled())
                 return 0;
-        if (page)
-                mem = try_get_mem_cgroup_from_swapcache(page);
-        if (!mem && mm)
-                mem = try_get_mem_cgroup_from_mm(mm);
-        if (unlikely(!mem))
-                return 0;
 
-        do {
-                progress = mem_cgroup_hierarchical_reclaim(mem,
-                                        gfp_mask, true, false);
-                progress += mem_cgroup_check_under_limit(mem);
-        } while (!progress && --retry);
+        ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
+        if (!ret)
+                mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */
 
-        css_put(&mem->css);
-        if (!retry)
-                return -ENOMEM;
-        return 0;
+        return ret;
 }
 
 static DEFINE_MUTEX(set_limit_mutex);
diff --git a/mm/shmem.c b/mm/shmem.c
index f9cb20ebb990..b25f95ce3db7 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1340,8 +1340,12 @@ repeat:
                         shmem_swp_unmap(entry);
                         spin_unlock(&info->lock);
                         if (error == -ENOMEM) {
-                                /* allow reclaim from this memory cgroup */
-                                error = mem_cgroup_shrink_usage(swappage,
+                                /*
+                                 * reclaim from proper memory cgroup and
+                                 * call memcg's OOM if needed.
+                                 */
+                                error = mem_cgroup_shmem_charge_fallback(
+                                                                swappage,
                                                                 current->mm,
                                                                 gfp);
                                 if (error) {