linux-kernel - Re: [PATCH v5 1/6] userfaultfd: convert mfill_atomic_pte

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Message-ID: <20230406213127.GB14244@monkey>
Date:   Thu, 6 Apr 2023 14:31:27 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peng Zhang <zhangpeng362@...wei.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, willy@...radead.org,
        sidhartha.kumar@...cle.com, vishal.moola@...il.com,
        muchun.song@...ux.dev, wangkefeng.wang@...wei.com,
        sunnanyong@...wei.com
Subject: Re: [PATCH v5 1/6] userfaultfd: convert mfill_atomic_pte_copy() to
 use a folio

On 03/31/23 17:39, Peng Zhang wrote:
> From: ZhangPeng <zhangpeng362@...wei.com>
> 
> Call vma_alloc_folio() directly instead of alloc_page_vma() and convert
> page_kaddr to kaddr in mfill_atomic_pte_copy(). Removes several calls to
> compound_head().
> 
> Signed-off-by: ZhangPeng <zhangpeng362@...wei.com>
> Reviewed-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
> ---
>  mm/userfaultfd.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)

Looks good,

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

>  	} else {
> -		page = *pagep;
> +		folio = page_folio(*pagep);
> +		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
>  		*pagep = NULL;
>  	}

However, I am still unsure about the reason for adding the VM_BUG_ON_FOLIO
here.
-- 
Mike Kravetz