linux-kernel - Re: [PATCH 2/2] mm/hugetlb: Use a folio in hugetlb

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Message-ID: <188bd60a-e58a-a0f7-727f-bb2ce2a40d94@huawei.com>
Date:   Mon, 5 Jun 2023 19:15:02 +0800
From:   "zhangpeng (AS)" <zhangpeng362@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <muchun.song@...ux.dev>, <sidhartha.kumar@...cle.com>,
        <vishal.moola@...il.com>, <wangkefeng.wang@...wei.com>,
        <sunnanyong@...wei.com>
Subject: Re: [PATCH 2/2] mm/hugetlb: Use a folio in hugetlb_wp()

On 2023/6/3 4:17, Matthew Wilcox wrote:

> On Fri, Jun 02, 2023 at 09:54:08AM +0800, Peng Zhang wrote:
>> From: ZhangPeng <zhangpeng362@...wei.com>
>>
>> We can replace nine implict calls to compound_head() with one by using
>> old_folio. However, we still need to keep old_page because we need to
>> know which page in the folio we are copying.
> Do we?  It's my understanding (and I am far from an expert here ...)
> that the 'pte_t *' we are passed *inside hugetlbfs* is not in fact a pte
> pointer at all but actually a pmd or pud pointer.  See how we do this:
>
>          pte_t pte = huge_ptep_get(ptep);
>
> and so the page we get back is always a head page, and we can go
> directly to a folio.  ie this is different from the THP cases.

Yes, I'll remove ptepage and old_page in a v2. Thanks.

Best Regards,
Peng