Re: [PATCH v4 1/6] userfaultfd: convert mfill_atomic_pte_copy() to use a folio

[Mike Kravetz]

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@xxxxxxxxxx>
> > > 
> > > 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