linux-kernel - Re: [PATCH v14 061/138] mm/migrate: Add folio_migrate

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Date:   Tue, 10 Aug 2021 22:09:25 +0100
From:   David Howells <dhowells@...hat.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     dhowells@...hat.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v14 061/138] mm/migrate: Add folio_migrate_flags()

Matthew Wilcox (Oracle) <willy@...radead.org> wrote:

> +	if (folio_test_error(folio))
> +		folio_set_error(newfolio);
> +	if (folio_test_referenced(folio))
> +		folio_set_referenced(newfolio);
> +	if (folio_test_uptodate(folio))
> +		folio_mark_uptodate(newfolio);
> +	if (folio_test_clear_active(folio)) {
> +		VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio);
> +		folio_set_active(newfolio);
> +	} else if (folio_test_clear_unevictable(folio))
> +		folio_set_unevictable(newfolio);
> +	if (folio_test_workingset(folio))
> +		folio_set_workingset(newfolio);
> +	if (folio_test_checked(folio))
> +		folio_set_checked(newfolio);
> +	if (folio_test_mappedtodisk(folio))
> +		folio_set_mappedtodisk(newfolio);

Since a bunch of these are bits in folio->flags and newfolio->flags, I wonder
if it's better to do use a cmpxchg() loop or LL/SC construct to transfer all
the relevant flags in one go.

Apart from that:

Reviewed-by: David Howells <dhowells@...hat.com>