On 1/7/19 5:43 AM, Catalin Marinas wrote:
> On Thu, Jan 03, 2019 at 06:07:35PM +0100, Michal Hocko wrote:
>>>> On Wed 02-01-19 13:06:19, Qian Cai wrote:
>>>> [...]
>>>>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
>>>>> index f9d9dc250428..9e1aa3b7df75 100644
>>>>> --- a/mm/kmemleak.c
>>>>> +++ b/mm/kmemleak.c
>>>>> @@ -576,6 +576,16 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
>>>>> struct rb_node **link, *rb_parent;
>>>>>
>>>>> object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
>>>>> +#ifdef CONFIG_PREEMPT_COUNT
>>>>> + if (!object) {
>>>>> + /* last-ditch effort in a low-memory situation */
>>>>> + if (irqs_disabled() || is_idle_task(current) || in_atomic())
>>>>> + gfp = GFP_ATOMIC;
>>>>> + else
>>>>> + gfp = gfp_kmemleak_mask(gfp) | __GFP_DIRECT_RECLAIM;
>>>>> + object = kmem_cache_alloc(object_cache, gfp);
>>>>> + }
>>>>> +#endif
> [...]
>> I will not object to this workaround but I strongly believe that
>> kmemleak should rethink the metadata allocation strategy to be really
>> robust.
>
> This would be nice indeed and it was discussed last year. I just haven't
> got around to trying anything yet:
>
> https://marc.info/?l=linux-mm&m=152812489819532
>
It could be helpful to apply this 10-line patch first if has no fundamental
issue, as it survives probably 50 times running LTP oom* workloads without a
single kmemleak allocation failure.
Of course, if someone is going to embed kmemleak metadata into slab objects
itself soon, this workaround is not needed.
