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.
Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Michal Hocko <mho...@suse.cz>
---
mm/memcontrol.c | 18 ++++--------------
1 file changed, 4 insertions(+), 14 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1780e66ec61e..cc7f3ca3ef34 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1071,7 +1071,7 @@ struct mem_cgroup *mem_cgroup_from_task(struct
task_struct *p)
return mem_cgroup_from_css(task_css(p, mem_cgroup_subsys_id));
}
-struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
+struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
{
struct mem_cgroup *memcg = NULL;
@@ -1079,7 +1079,7 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct
mm_struct *mm)
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 @@ bool task_in_mem_cgroup(struct task_struct *task,
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 @@ bool task_in_mem_cgroup(struct task_struct *task,
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
@@ -3649,15 +3647,7 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup
**_memcg, int order)
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);
--
1.9.0
--
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