linux-kernel - Re: [PATCH v2] mm/hugetlb: remove redundant reservation check condition in alloc_huge

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Message-ID: <e7b7532a-6087-7307-1f89-f7db26004bae@oracle.com>
Date:   Tue, 2 Mar 2021 13:54:22 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/hugetlb: remove redundant reservation check
 condition in alloc_huge_page()

On 3/1/21 2:47 AM, Miaohe Lin wrote:
> vma_resv_map(vma) checks if a reserve map is associated with the vma.  The
> routine vma_needs_reservation() will check vma_resv_map(vma) and return 1
> if no reserv map is present.  map_chg is set to the return value of
> vma_needs_reservation().  Therefore, !vma_resv_map(vma) is redundant in the
> expression:
> 	map_chg || avoid_reserve || !vma_resv_map(vma);
> Remove the redundant check.
> 
> [Thanks Mike Kravetz for reshaping this commit message!]
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Thanks,

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>

> ---
>  mm/hugetlb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 60c67eb016f7..060005b868cf 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2314,7 +2314,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
>  
>  	/* If this allocation is not consuming a reservation, charge it now.
>  	 */
> -	deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma);
> +	deferred_reserve = map_chg || avoid_reserve;
>  	if (deferred_reserve) {
>  		ret = hugetlb_cgroup_charge_cgroup_rsvd(
>  			idx, pages_per_huge_page(h), &h_cg);
>