diff options
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c0500e4d3a2..36896f3eb7f 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -250,6 +250,14 @@ static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont) struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p) { + /* + * mm_update_next_owner() may clear mm->owner to NULL + * if it races with swapoff, page migration, etc. + * So this can be called with p == NULL. + */ + if (unlikely(!p)) + return NULL; + return container_of(task_subsys_state(p, mem_cgroup_subsys_id), struct mem_cgroup, css); } @@ -549,6 +557,11 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm, if (likely(!memcg)) { rcu_read_lock(); mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); + if (unlikely(!mem)) { + rcu_read_unlock(); + kmem_cache_free(page_cgroup_cache, pc); + return 0; + } /* * For every charge from the cgroup, increment reference count */ @@ -801,6 +814,10 @@ int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask) rcu_read_lock(); mem = mem_cgroup_from_task(rcu_dereference(mm->owner)); + if (unlikely(!mem)) { + rcu_read_unlock(); + return 0; + } css_get(&mem->css); rcu_read_unlock(); |