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Date:   Sat, 21 May 2022 13:01:33 +0800
From:   Chih-En Lin <shiyn.lin@gmail.com>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
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Subject: Re: [RFC PATCH 3/6] mm, pgtable: Add ownership for the PTE table
Message-ID: <20220521050133.GD1508515@strix-laptop>
References: <20220519183127.3909598-1-shiyn.lin@gmail.com>
 <20220519183127.3909598-4-shiyn.lin@gmail.com>
 <YohkY75ekI6vhMYC@casper.infradead.org>
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On Sat, May 21, 2022 at 05:02:43AM +0100, Matthew Wilcox wrote:
> On Fri, May 20, 2022 at 02:31:24AM +0800, Chih-En Lin wrote:
> > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > index 8834e38c06a4..5dcbd7f6c361 100644
> > --- a/include/linux/mm_types.h
> > +++ b/include/linux/mm_types.h
> > @@ -221,6 +221,7 @@ struct page {
> >  #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
> >  	int _last_cpupid;
> >  #endif
> > +	pmd_t *cow_pte_owner; /* cow pte: pmd */
> 
> This is definitely the wrong place.  I think it could replace _pt_pad_1,
> since it's a pointer to a PMD and so the bottom bit will definitely
> be clear.
>

I will figure out how to use _pt_pad_1.
It seems relative to the compound page (or folio?).

Thanks.