memcg: get_mem_cgroup_from_mm()
Instead of returning NULL from try_get_mem_cgroup_from_mm() when the mm
owner is exiting, just return root_mem_cgroup. This makes sense for all
callsites and gets rid of some of them having to fallback manually.
[fengguang.wu@intel.com: fix warnings]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c3b674f..87c3ec3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1071,7 +1071,7 @@
return mem_cgroup_from_css(task_css(p, memory_cgrp_id));
}
-struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
+static struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
{
struct mem_cgroup *memcg = NULL;
@@ -1079,7 +1079,7 @@
do {
memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
if (unlikely(!memcg))
- break;
+ memcg = root_mem_cgroup;
} while (!css_tryget(&memcg->css));
rcu_read_unlock();
return memcg;
@@ -1475,7 +1475,7 @@
p = find_lock_task_mm(task);
if (p) {
- curr = try_get_mem_cgroup_from_mm(p->mm);
+ curr = get_mem_cgroup_from_mm(p->mm);
task_unlock(p);
} else {
/*
@@ -1489,8 +1489,6 @@
css_get(&curr->css);
rcu_read_unlock();
}
- if (!curr)
- return false;
/*
* We should check use_hierarchy of "memcg" not "curr". Because checking
* use_hierarchy of "curr" here make this function true if hierarchy is
@@ -3617,15 +3615,7 @@
if (!current->mm || current->memcg_kmem_skip_account)
return true;
- memcg = try_get_mem_cgroup_from_mm(current->mm);
-
- /*
- * very rare case described in mem_cgroup_from_task. Unfortunately there
- * isn't much we can do without complicating this too much, and it would
- * be gfp-dependent anyway. Just let it go
- */
- if (unlikely(!memcg))
- return true;
+ memcg = get_mem_cgroup_from_mm(current->mm);
if (!memcg_can_account_kmem(memcg)) {
css_put(&memcg->css);