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-rw-r--r--mm/memcontrol.c37
1 files changed, 33 insertions, 4 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b836e7f00309..bf9cf738c836 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -678,9 +678,20 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
}
EXPORT_SYMBOL(mem_cgroup_from_task);
-static struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
+/**
+ * get_mem_cgroup_from_mm: Obtain a reference on given mm_struct's memcg.
+ * @mm: mm from which memcg should be extracted. It can be NULL.
+ *
+ * Obtain a reference on mm->memcg and returns it if successful. Otherwise
+ * root_mem_cgroup is returned. However if mem_cgroup is disabled, NULL is
+ * returned.
+ */
+struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
{
- struct mem_cgroup *memcg = NULL;
+ struct mem_cgroup *memcg;
+
+ if (mem_cgroup_disabled())
+ return NULL;
rcu_read_lock();
do {
@@ -700,6 +711,24 @@ static struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
rcu_read_unlock();
return memcg;
}
+EXPORT_SYMBOL(get_mem_cgroup_from_mm);
+
+/**
+ * If current->active_memcg is non-NULL, do not fallback to current->mm->memcg.
+ */
+static __always_inline struct mem_cgroup *get_mem_cgroup_from_current(void)
+{
+ if (unlikely(current->active_memcg)) {
+ struct mem_cgroup *memcg = root_mem_cgroup;
+
+ rcu_read_lock();
+ if (css_tryget_online(&current->active_memcg->css))
+ memcg = current->active_memcg;
+ rcu_read_unlock();
+ return memcg;
+ }
+ return get_mem_cgroup_from_mm(current->mm);
+}
/**
* mem_cgroup_iter - iterate over memory cgroup hierarchy
@@ -2261,7 +2290,7 @@ struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
if (current->memcg_kmem_skip_account)
return cachep;
- memcg = get_mem_cgroup_from_mm(current->mm);
+ memcg = get_mem_cgroup_from_current();
kmemcg_id = READ_ONCE(memcg->kmemcg_id);
if (kmemcg_id < 0)
goto out;
@@ -2345,7 +2374,7 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
if (memcg_kmem_bypass())
return 0;
- memcg = get_mem_cgroup_from_mm(current->mm);
+ memcg = get_mem_cgroup_from_current();
if (!mem_cgroup_is_root(memcg)) {
ret = memcg_kmem_charge_memcg(page, gfp, order, memcg);
if (!ret)
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