linux-kernel - Re: [PATCH RFC 08/29] mm/migrate: rename putback_movable_folio() to putback_movable_ops

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Message-ID: <AD158968-D369-4884-806A-18AEE2293C8B@nvidia.com>
Date: Wed, 18 Jun 2025 15:10:10 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
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Subject: Re: [PATCH RFC 08/29] mm/migrate: rename putback_movable_folio() to
 putback_movable_ops_page()

On 18 Jun 2025, at 13:39, David Hildenbrand wrote:

> ... and factor the complete handling of movable_ops pages out.
> Convert it similar to isolate_movable_ops_page().
>
> While at it, convert the VM_BUG_ON_FOLIO() into a VM_WARN_ON_PAGE().
>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/migrate.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 6bbb455f8b593..32e77898f7d6c 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -133,12 +133,30 @@ bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
>  	return false;
>  }
>
> -static void putback_movable_folio(struct folio *folio)
> +/**
> + * putback_movable_ops_page - putback an isolated movable_ops page
> + * @page: The isolated page.
> + *
> + * Putback an isolated movable_ops page.
> + *
> + * After the page was putback, it might get freed instantly.
> + */
> +static void putback_movable_ops_page(struct page *page)
>  {
> -	const struct movable_operations *mops = folio_movable_ops(folio);
> -
> -	mops->putback_page(&folio->page);
> -	folio_clear_isolated(folio);
> +	/*
> +	 * TODO: these pages will not be folios in the future. All
> +	 * folio dependencies will have to be removed.
> +	 */
> +	struct folio *folio = page_folio(page);
> +
> +	VM_WARN_ON_ONCE_PAGE(!PageIsolated(page), page);
> +	folio_lock(folio);
> +	/* If the page was released by it's owner, there is nothing to do. */
> +	if (PageMovable(page))
> +		page_movable_ops(page)->putback_page(page);
> +	ClearPageIsolated(page);
> +	folio_unlock(folio);
> +	folio_put(folio);

Why not use page version of lock, unlock, and put? Especially you are
thinking about not using folio for these pages. Just a question,
I am OK with current patch.

>  }
>
>  /*
> @@ -166,14 +184,7 @@ void putback_movable_pages(struct list_head *l)
>  		 * have PAGE_MAPPING_MOVABLE.
>  		 */
>  		if (unlikely(__folio_test_movable(folio))) {
> -			VM_BUG_ON_FOLIO(!folio_test_isolated(folio), folio);
> -			folio_lock(folio);
> -			if (folio_test_movable(folio))
> -				putback_movable_folio(folio);
> -			else
> -				folio_clear_isolated(folio);
> -			folio_unlock(folio);
> -			folio_put(folio);
> +			putback_movable_ops_page(&folio->page);
>  		} else {
>  			node_stat_mod_folio(folio, NR_ISOLATED_ANON +
>  					folio_is_file_lru(folio), -folio_nr_pages(folio));
> -- 
> 2.49.0

Acked-by: Zi Yan <ziy@...dia.com>

Best Regards,
Yan, Zi