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

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Date:   Mon, 26 Sep 2022 16:34:00 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Qi Zheng <zhengqi.arch@...edance.com>, akpm@...ux-foundation.org,
        muchun.song@...ux.dev
Cc:     chris@...kel.net, jcmvbkbc@...il.com, maobibo@...ngson.cn,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>,
        Bibo Mao <maobibo@...ngson.cn>
Subject: Re: [PATCH v2] mm: use update_mmu_tlb() on the second thread

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,

David / dhildenb