memcg: fix swapcache charge from kernel thread context

[cascardo/linux.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c47dffd..5177c6d 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1077,9 +1077,18 @@ static struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
 
        rcu_read_lock();
        do {
-               memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
-               if (unlikely(!memcg))
+               /*
+                * Page cache insertions can happen withou an
+                * actual mm context, e.g. during disk probing
+                * on boot, loopback IO, acct() writes etc.
+                */
+               if (unlikely(!mm))
                        memcg = root_mem_cgroup;
+               else {
+                       memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
+                       if (unlikely(!memcg))
+                               memcg = root_mem_cgroup;
+               }
        } while (!css_tryget(&memcg->css));
        rcu_read_unlock();
        return memcg;
@@ -3958,17 +3967,9 @@ int mem_cgroup_charge_file(struct page *page, struct mm_struct *mm,
                return 0;
        }
 
-       /*
-        * Page cache insertions can happen without an actual mm
-        * context, e.g. during disk probing on boot.
-        */
-       if (unlikely(!mm))
-               memcg = root_mem_cgroup;
-       else {
-               memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, 1, true);
-               if (!memcg)
-                       return -ENOMEM;
-       }
+       memcg = mem_cgroup_try_charge_mm(mm, gfp_mask, 1, true);
+       if (!memcg)
+               return -ENOMEM;
        __mem_cgroup_commit_charge(memcg, page, 1, type, false);
        return 0;
 }