linux-kernel - Re: [PATCH v2] hugetlbfs: remove meaningless variable avoid

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Message-ID: <9d129083-e273-3278-b188-b55bfa2b08d1@oracle.com>
Date:   Thu, 21 Jan 2021 11:02:40 -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] hugetlbfs: remove meaningless variable avoid_reserve

On 1/19/21 11:15 PM, Miaohe Lin wrote:
> The variable avoid_reserve is meaningless because we never changed its
> value and just passed it to alloc_huge_page(). So remove it to make code
> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
> hugepage yet. Also add a comment offered by Mike Kravetz to explain this.
> 
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> ---
>  fs/hugetlbfs/inode.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)

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

> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 4bbfd78a7ccb..14df2f73b8ef 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>  		 */
>  		struct page *page;
>  		unsigned long addr;
> -		int avoid_reserve = 0;
>  
>  		cond_resched();
>  
> @@ -716,8 +715,15 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>  			continue;
>  		}
>  
> -		/* Allocate page and add to page cache */
> -		page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
> +		/*
> +		 * Allocate page without setting the avoid_reserve argument.
> +		 * There certainly are no reserves associated with the
> +		 * pseudo_vma.  However, there could be shared mappings with
> +		 * reserves for the file at the inode level.  If we fallocate
> +		 * pages in these areas, we need to consume the reserves
> +		 * to keep reservation accounting consistent.
> +		 */
> +		page = alloc_huge_page(&pseudo_vma, addr, 0);
>  		hugetlb_drop_vma_policy(&pseudo_vma);
>  		if (IS_ERR(page)) {
>  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> 


-- 
Mike Kravetz