linux-kernel - Re: [PATCH v2 1/8] mm: migrate: remove PageTransHuge check in numamigrate_isolate

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Message-ID: <ebf94247-e77e-4265-880a-1d74a74c76f6@huawei.com>
Date:   Mon, 21 Aug 2023 20:52:27 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <ying.huang@...el.com>,
        <david@...hat.com>, Zi Yan <ziy@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>, <hughd@...gle.com>
Subject: Re: [PATCH v2 1/8] mm: migrate: remove PageTransHuge check in
 numamigrate_isolate_page()



On 2023/8/21 20:38, Matthew Wilcox wrote:
> On Mon, Aug 21, 2023 at 07:56:17PM +0800, Kefeng Wang wrote:
>> Since we begin to convert the numa migration code to use folio, which
>> could let us to handle arbitrary sizes of folio, so drop assert that
>> we only support PageTransHuge page(PMD size) when order > 0.
> 
> Have you looked at the implementation of PageTransHuge()?  Your
> description doesn't match what the code does.

oops, not only PMD size...

> 
>> Suggested-by: Matthew Wilcox (Oracle) <willy@...radead.org>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>> ---
>>   mm/migrate.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index b7fa020003f3..646d8ee7f102 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -2483,8 +2483,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>>   	int nr_pages = thp_nr_pages(page);
>>   	int order = compound_order(page);
>>   
>> -	VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
>> -
>>   	/* Do not migrate THP mapped by multiple processes */
>>   	if (PageTransHuge(page) && total_mapcount(page) > 1)
>>   		return 0;
>> -- 
>> 2.41.0
>>
>>
>