[PATCH v3] memcg: Fix memcg_kmem_bypass() for remote memcg charging

Zefan Li
2020-05-26T01:25:25Z

While trying to use remote memcg charging in an out-of-tree kernel module
I found it's not working, because the current thread is a workqueue thread.

As we will probably encounter this issue in the future as the users of
memalloc_use_memcg() grow, and it's nothing wrong for this usage, it's
better we fix it now.

Acked-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Signed-off-by: Zefan Li <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---

v3: bypass __GFP_ACCOUNT allocations in interrupt contexts.

---
mm/memcontrol.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a3b97f1..3c7717a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2802,7 +2802,12 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,

static inline bool memcg_kmem_bypass(void)
{
- if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD))
+ if (in_interrupt())
+ return true;
+
+ /* Allow remote memcg charging in kthread contexts. */
+ if ((!current->mm || (current->flags & PF_KTHREAD)) &&
+ !current->active_memcg)
return true;
return false;
}
--
2.7.4