linux-kernel - Re: [PATCH 1/4] mm: migrate: use a folio in add_page_for

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Date:   Wed, 2 Aug 2023 13:21:53 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Huang Ying <ying.huang@...el.com>,
        David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH 1/4] mm: migrate: use a folio in add_page_for_migration()

On Wed, Aug 02, 2023 at 05:53:43PM +0800, Kefeng Wang wrote:
>  	err = -EACCES;
> -	if (page_mapcount(page) > 1 && !migrate_all)
> -		goto out_putpage;
> +	if (folio_estimated_sharers(folio) > 1 && !migrate_all)
> +		goto out_putfolio;

I do not think this is the correct change.  Maybe leave this line
alone.

> -	if (PageHuge(page)) {
> -		if (PageHead(page)) {
> -			isolated = isolate_hugetlb(page_folio(page), pagelist);
> +	if (folio_test_hugetlb(folio)) {
> +		if (folio_test_large(folio)) {

This makes no sense when you read it.  All hugetlb folios are large,
by definition.  Think about what this code used to do, and what it
should be changed to.

> +			isolated = isolate_hugetlb(folio, pagelist);
>  			err = isolated ? 1 : -EBUSY;
>  		}
>  	} else {
> -		struct page *head;
> -
> -		head = compound_head(page);
> -		isolated = isolate_lru_page(head);
> +		isolated = folio_isolate_lru(folio);
>  		if (!isolated) {
>  			err = -EBUSY;
> -			goto out_putpage;
> +			goto out_putfolio;
>  		}
>  
>  		err = 1;
> -		list_add_tail(&head->lru, pagelist);
> -		mod_node_page_state(page_pgdat(head),
> -			NR_ISOLATED_ANON + page_is_file_lru(head),
> -			thp_nr_pages(head));
> +		list_add_tail(&folio->lru, pagelist);
> +		node_stat_mod_folio(folio,
> +			NR_ISOLATED_ANON + folio_is_file_lru(folio),
> +			folio_nr_pages(folio));
>  	}