linux-kernel - Re: [RFC 1/2] migrate: convert unmap_and

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Date:   Tue, 01 Nov 2022 10:54:48 -0400
From:   Zi Yan <ziy@...dia.com>
To:     Huang Ying <ying.huang@...el.com>
Cc:     linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yang Shi <shy828301@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [RFC 1/2] migrate: convert unmap_and_move() to use folios

On 1 Nov 2022, at 2:21, Huang Ying wrote:

> Quite straightforward, the page functions are converted to
> corresponding folio functions.  Same for comments.
>
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Zi Yan <ziy@...dia.com>
> Cc: Yang Shi <shy828301@...il.com>
> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Matthew Wilcox <willy@...radead.org>
> ---
>  mm/migrate.c | 54 ++++++++++++++++++++++++++--------------------------
>  1 file changed, 27 insertions(+), 27 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index dff333593a8a..e625fd84b824 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1150,79 +1150,79 @@ static int __unmap_and_move(struct folio *src, struct folio *dst,
>  }
>
>  /*
> - * Obtain the lock on page, remove all ptes and migrate the page
> - * to the newly allocated page in newpage.
> + * Obtain the lock on folio, remove all ptes and migrate the folio
> + * to the newly allocated folio in dst.
>   */
>  static int unmap_and_move(new_page_t get_new_page,
>  				   free_page_t put_new_page,
> -				   unsigned long private, struct page *page,
> +				   unsigned long private, struct folio *src,
>  				   int force, enum migrate_mode mode,
>  				   enum migrate_reason reason,
>  				   struct list_head *ret)
>  {
> -	struct folio *dst, *src = page_folio(page);
> +	struct folio *dst;
>  	int rc = MIGRATEPAGE_SUCCESS;
>  	struct page *newpage = NULL;
>
> -	if (!thp_migration_supported() && PageTransHuge(page))
> +	if (!thp_migration_supported() && folio_test_large(src))

folio_test_transhuge() should be used.

>  		return -ENOSYS;
>
> -	if (page_count(page) == 1) {
> -		/* Page was freed from under us. So we are done. */
> -		ClearPageActive(page);
> -		ClearPageUnevictable(page);
> +	if (folio_ref_count(src) == 1) {
> +		/* Folio was freed from under us. So we are done. */
> +		folio_clear_active(src);
> +		folio_clear_unevictable(src);
>  		/* free_pages_prepare() will clear PG_isolated. */
>  		goto out;
>  	}
>
> -	newpage = get_new_page(page, private);
> +	newpage = get_new_page(&src->page, private);
>  	if (!newpage)
>  		return -ENOMEM;
>  	dst = page_folio(newpage);
>
> -	newpage->private = 0;
> +	dst->private = 0;
>  	rc = __unmap_and_move(src, dst, force, mode);
>  	if (rc == MIGRATEPAGE_SUCCESS)
> -		set_page_owner_migrate_reason(newpage, reason);
> +		set_page_owner_migrate_reason(&dst->page, reason);
>
>  out:
>  	if (rc != -EAGAIN) {
>  		/*
> -		 * A page that has been migrated has all references
> -		 * removed and will be freed. A page that has not been
> +		 * A folio that has been migrated has all references
> +		 * removed and will be freed. A folio that has not been
>  		 * migrated will have kept its references and be restored.
>  		 */
> -		list_del(&page->lru);
> +		list_del(&src->lru);
>  	}
>
>  	/*
>  	 * If migration is successful, releases reference grabbed during
> -	 * isolation. Otherwise, restore the page to right list unless
> +	 * isolation. Otherwise, restore the folio to right list unless
>  	 * we want to retry.
>  	 */
>  	if (rc == MIGRATEPAGE_SUCCESS) {
>  		/*
> -		 * Compaction can migrate also non-LRU pages which are
> +		 * Compaction can migrate also non-LRU folios which are
>  		 * not accounted to NR_ISOLATED_*. They can be recognized
> -		 * as __PageMovable
> +		 * as __folio_test_movable
>  		 */
> -		if (likely(!__PageMovable(page)))
> -			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
> -					page_is_file_lru(page), -thp_nr_pages(page));
> +		if (likely(!__folio_test_movable(src)))
> +			mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
> +					folio_is_file_lru(src), -folio_nr_pages(src));
>
>  		if (reason != MR_MEMORY_FAILURE)
>  			/*
> -			 * We release the page in page_handle_poison.
> +			 * We release the folio in page_handle_poison.
>  			 */
> -			put_page(page);
> +			folio_put(src);
>  	} else {
>  		if (rc != -EAGAIN)
> -			list_add_tail(&page->lru, ret);
> +			list_add_tail(&src->lru, ret);
>
>  		if (put_new_page)
> -			put_new_page(newpage, private);
> +			put_new_page(&dst->page, private);
>  		else
> -			put_page(newpage);
> +			folio_put(dst);
>  	}
>
>  	return rc;
> @@ -1459,7 +1459,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>  						&ret_pages);
>  			else
>  				rc = unmap_and_move(get_new_page, put_new_page,
> -						private, page, pass > 2, mode,
> +						private, page_folio(page), pass > 2, mode,
>  						reason, &ret_pages);
>  			/*
>  			 * The rules are:
> -- 
> 2.35.1

Everything else looks good to me.

--
Best Regards,
Yan, Zi

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