1 files changed, 15 insertions, 25 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2fc6d6c48238..01c2d8f14685 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -932,7 +932,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
         if (unlikely(!mem))
                 return 0;
 
-        VM_BUG_ON(mem_cgroup_is_obsolete(mem));
+        VM_BUG_ON(!mem || mem_cgroup_is_obsolete(mem));
 
         while (1) {
                 int ret;
@@ -1024,9 +1024,7 @@ static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
                 return NULL;
 
         pc = lookup_page_cgroup(page);
-        /*
-         * Used bit of swapcache is solid under page lock.
-         */
+        lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 mem = pc->mem_cgroup;
                 if (mem && !css_tryget(&mem->css))
@@ -1040,6 +1038,7 @@ static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
                         mem = NULL;
                 rcu_read_unlock();
         }
+        unlock_page_cgroup(pc);
         return mem;
 }
 
@@ -1618,37 +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);