linux-kernel - Re: [PATCH v2] mm: use update_mmu

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Date:   Thu, 29 Sep 2022 11:07:22 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        muchun.song@...ux.dev, maobibo@...ngson.cn
Cc:     chris@...kel.net, jcmvbkbc@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH v2] mm: use update_mmu_tlb() on the second thread



On 2022/9/26 22:34, David Hildenbrand wrote:
> On 26.09.22 13:56, Qi Zheng wrote:
>> As message in commit 7df676974359 ("mm/memory.c: Update local TLB
>> if PTE entry exists") said, we should update local TLB only on the
>> second thread. So in the do_anonymous_page() here, we should use
>> update_mmu_tlb() instead of update_mmu_cache() on the second thread.
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
>> Reviewed-by: Muchun Song <songmuchun@...edance.com>
>> ---
>> v1: 
>> https://lore.kernel.org/lkml/20220924053239.91661-1-zhengqi.arch@bytedance.com/
>>
>> Changelog in v1 -> v2:
>>   - change the subject and commit message (David)
>>
>>   mm/memory.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 118e5f023597..9e11c783ba0e 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4122,7 +4122,7 @@ static vm_fault_t do_anonymous_page(struct 
>> vm_fault *vmf)
>>       vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
>>               &vmf->ptl);
>>       if (!pte_none(*vmf->pte)) {
>> -        update_mmu_cache(vma, vmf->address, vmf->pte);
>> +        update_mmu_tlb(vma, vmf->address, vmf->pte);
>>           goto release;
>>       }
> 
> 
> Staring at 7df676974359, it indeed looks like an accidental use [nothing 
> else in that patch uses update_mmu_cache].
> 
> So it looks good to me, but a confirmation from Bibo Mao might be good.

Thanks, and Hi Bibo, any comments here? :)

> 

-- 
Thanks,
Qi