linux-kernel - Re: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing

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Date:   Thu, 02 Apr 2020 09:49:33 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Zi Yan <ziy@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jérôme Glisse <jglisse@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Subject: Re: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing

Zi Yan <ziy@...dia.com> writes:

> On 31 Mar 2020, at 4:56, Huang, Ying wrote:
>>
>> From: Huang Ying <ying.huang@...el.com>
>> -       /* FOLL_DUMP will return -EFAULT on huge zero page */
>> -       page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
>> +       if (pmd_present(*pmd)) {
>> +               /* FOLL_DUMP will return -EFAULT on huge zero page */
>> +               page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
>> +       } else if (unlikely(is_swap_pmd(*pmd))) {
>
> Should be:
>           } else if (unlikely(thp_migration_support() && is_swap_pmd(*pmd))) {

Thought this again.  This can reduce the code size if
thp_migration_support() isn't enabled.  I will do this in the next
version.

Best Regards,
Huang, Ying