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Message-ID: <c4186f18-5a49-4fd6-ab19-6db77bcfc541@huawei.com>
Date:   Mon, 6 Nov 2023 23:08:56 +0800
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Subject: Re: [PATCH v2 06/10] mm: memory: use a folio in zap_pte_range()
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To:     Matthew Wilcox <willy@infradead.org>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        David Hildenbrand <david@redhat.com>,
        <linux-s390@vger.kernel.org>
References: <20231104035522.2418660-1-wangkefeng.wang@huawei.com>
 <20231104035522.2418660-7-wangkefeng.wang@huawei.com>
 <ZUZ9dg4YHZdUKDqO@casper.infradead.org>
 <e3c275c3-e09d-4495-8132-9464133db283@huawei.com>
 <ZUj2SCML4h7X5TWu@casper.infradead.org>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
In-Reply-To: <ZUj2SCML4h7X5TWu@casper.infradead.org>
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On 2023/11/6 22:20, Matthew Wilcox wrote:
> On Mon, Nov 06, 2023 at 10:30:59AM +0800, Kefeng Wang wrote:
>> On 2023/11/5 1:20, Matthew Wilcox wrote:
>>>> -				page_remove_rmap(page, vma, false);
>>>> -			put_page(page);
>>>> +				page_remove_rmap(&folio->page, vma, false);
>>>> +			folio_put(folio);
>>>
>>> This is wrong.  If we have a PTE-mapped THP, you'll remove the head page
>>> N times instead of removing each of N pages.
>>
>> This is device private entry, I suppose that it won't be a THP and large
>> folio when check migrate_vma_check_page() and migrate_vma_insert_page(),
>> right?
> 
> I don't want to leave that kind of booby-trap in the code.  Both places
> which currently call page_remove_rmap() should be left as referring to
> the page, not the folio.

Sure, I will fix this, also page_try_dup_anon_rmap() for device private
entry in copy_nonpresent_pte of patch5.