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

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Date:   Thu, 18 Feb 2021 10:27:07 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/hugetlb: remove redundant reservation check condition
 in alloc_huge_page()

Hi:
On 2021/2/13 9:15, Mike Kravetz wrote:
> On 2/9/21 11:54 PM, Miaohe Lin wrote:
>> If there is no reservation corresponding to a vma, map_chg is always != 0,
>> i.e. we can not meet the condition where a vma does not have reservation
>> while map_chg = 0.
> 
> This commit message might be easier to understand?
> 
> 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.
> 

Sorry for late respond! I will use this wonderful commit message. Many thanks! :)