linux-kernel - Re: [PATCH v2 2/6] mm/migrate_device: further convert migrate_device

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Message-ID: <Zc_Y41y_hOqsmsDx@casper.infradead.org>
Date: Fri, 16 Feb 2024 21:51:31 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, apopple@...dia.com
Subject: Re: [PATCH v2 2/6] mm/migrate_device: further convert
 migrate_device_unmap()  to folios

On Fri, Feb 16, 2024 at 01:13:16PM -0800, Sidhartha Kumar wrote:
> migrate_device_unmap() already has a folio, we can use the folio
> versions of is_zone_device_page() and putback_lru_page.
> -		if (page_mapped(page) ||
> -		    !migrate_vma_check_page(page, fault_page)) {
> -			if (!is_zone_device_page(page)) {
> -				get_page(page);
> -				putback_lru_page(page);
> +		if (folio_mapped(folio) ||
> +		    !migrate_vma_check_page(&folio->page, fault_page)) {
> +			if (!folio_is_zone_device(folio)) {
> +				folio_get(folio);
> +				folio_putback_lru(folio);

page_mapped() is not the same thing as folio_mapped(page_folio(page)).
please include some argumentation about why this is a correct
transformation to make.