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Date:   Thu, 6 Apr 2023 14:28:48 -0700
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Sidhartha Kumar <sidhartha.kumar@oracle.com>,
        Peng Zhang <zhangpeng362@huawei.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        vishal.moola@gmail.com, muchun.song@linux.dev,
        wangkefeng.wang@huawei.com, sunnanyong@huawei.com
Subject: Re: [PATCH v4 1/6] userfaultfd: convert mfill_atomic_pte_copy() to
 use a folio
Message-ID: <20230406212848.GA28429@monkey>
References: <20230330134045.375163-1-zhangpeng362@huawei.com>
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 <765d450c-2ff6-1420-b94f-528d56bffee4@oracle.com>
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On 03/30/23 19:02, Matthew Wilcox wrote:
> On Thu, Mar 30, 2023 at 10:02:52AM -0700, Sidhartha Kumar wrote:
> > On 3/30/23 6:40 AM, Peng Zhang wrote:
> > > From: ZhangPeng <zhangpeng362@huawei.com>
> > > 
> > > Call vma_alloc_folio() directly instead of alloc_page_vma(). Add an
> > > assertion that this is a single-page folio and removes several calls to
> > > compound_head().
> 
> There's no added assertion in this patch any more, so I'd drop that
> part of the description.
> 

I thought it was this.

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

I was wondering what that VM_BUG_ON_FOLIO was added?
-- 
Mike Kravetz