Re: [Intel-gfx] [PATCH rdma-next v3 1/2] lib/scatterlist: Add support in dynamic allocation of SG table from pages

[Maor Gottlieb <maorg@nvidia.com>]

On 9/25/2020 3:33 PM, Tvrtko Ursulin wrote:
>
> On 25/09/2020 13:18, Maor Gottlieb wrote:
>> On 9/25/2020 2:55 PM, Jason Gunthorpe wrote:
>>> On Fri, Sep 25, 2020 at 10:13:30AM +0300, Leon Romanovsky wrote:
>>>>>> diff --git a/tools/testing/scatterlist/main.c 
>>>>>> b/tools/testing/scatterlist/main.c
>>>>>> index 0a1464181226..4899359a31ac 100644
>>>>>> +++ b/tools/testing/scatterlist/main.c
>>>>>> @@ -55,14 +55,13 @@ int main(void)
>>>>>>        for (i = 0, test = tests; test->expected_segments; test++, 
>>>>>> i++) {
>>>>>>            struct page *pages[MAX_PAGES];
>>>>>>            struct sg_table st;
>>>>>> -        int ret;
>>>>>> +        struct scatterlist *sg;
>>>>>>
>>>>>>            set_pages(pages, test->pfn, test->num_pages);
>>>>>>
>>>>>> -        ret = __sg_alloc_table_from_pages(&st, pages, 
>>>>>> test->num_pages,
>>>>>> -                          0, test->size, test->max_seg,
>>>>>> -                          GFP_KERNEL);
>>>>>> -        assert(ret == test->alloc_ret);
>>>>>> +        sg = __sg_alloc_table_from_pages(&st, pages, 
>>>>>> test->num_pages, 0,
>>>>>> +                test->size, test->max_seg, NULL, 0, GFP_KERNEL);
>>>>>> +        assert(PTR_ERR_OR_ZERO(sg) == test->alloc_ret);
>>>>> Some test coverage for relatively complex code would be very 
>>>>> welcomed. Since
>>>>> the testing framework is already there, even if it bit-rotted a 
>>>>> bit, but
>>>>> shouldn't be hard to fix.
>>>>>
>>>>> A few tests to check append/grow works as expected, in terms of 
>>>>> how the end
>>>>> table looks like given the initial state and some different page 
>>>>> patterns
>>>>> added to it. And both crossing and not crossing into sg chaining 
>>>>> scenarios.
>>>> This function is basic for all RDMA devices and we are pretty 
>>>> confident
>>>> that the old and new flows are tested thoroughly.
>>> Well, since 0-day is reporting that __i915_gem_userptr_alloc_pages is
>>> crashing on this, it probably does need some tests :\
>>>
>>> Jason
>>
>> It is crashing in the regular old flow which already tested.
>> However, I will add more tests.
>
> Do you want to take some of the commits from 
> git://people.freedesktop.org/~tursulin/drm-intel sgtest? It would be 
> fine by me. I can clean up the commit messages if you want.

I will very appreciate it. Thanks
>
> https://cgit.freedesktop.org/~tursulin/drm-intel/commit/?h=sgtest&id=79102f4d795c4769431fc44a6cf7ed5c5b1b5214 
> - this one undoes the bit rot and makes the test just work on the 
> current kernel.
>
> https://cgit.freedesktop.org/~tursulin/drm-intel/commit/?h=sgtest&id=b09bfe80486c4d93ee1d8ae17d5b46397b1c6ee1 
> - this one you probably should squash in your patch. Minus the zeroing 
> of struct sg_stable since that would hide the issue.
>
> https://cgit.freedesktop.org/~tursulin/drm-intel/commit/?h=sgtest&id=97f5df37e612f798ced90541eece13e2ef639181 
> - final commit is optional but I guess handy for debugging.
>
> Regards,
>
> Tvrtko