linux-kernel - Re: [PATCH] mm/thp: make set_huge_zero

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Message-ID: <20191001115239.dqodyji3r32zjkea@box>
Date:   Tue, 1 Oct 2019 14:52:39 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ralph Campbell <rcampbell@...dia.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/thp: make set_huge_zero_page() return void

On Mon, Sep 30, 2019 at 12:55:28PM -0700, Ralph Campbell wrote:
> The return value from set_huge_zero_page() is never checked so simplify
> the code by making it return void.
> 
> Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
> ---
>  mm/huge_memory.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index c5cb6dcd6c69..6cf0ee65538d 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -686,20 +686,18 @@ static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
>  }
>  
>  /* Caller must hold page table lock. */
> -static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
> +static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
>  		struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
>  		struct page *zero_page)
>  {
>  	pmd_t entry;
> -	if (!pmd_none(*pmd))
> -		return false;
> +

Wat? So you just bindly overwrite whatever is there?

NAK.

>  	entry = mk_pmd(zero_page, vma->vm_page_prot);
>  	entry = pmd_mkhuge(entry);
>  	if (pgtable)
>  		pgtable_trans_huge_deposit(mm, pmd, pgtable);
>  	set_pmd_at(mm, haddr, pmd, entry);
>  	mm_inc_nr_ptes(mm);
> -	return true;
>  }
>  
>  vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
> -- 
> 2.20.1
> 
> 

-- 
 Kirill A. Shutemov