linux-kernel - Re: [PATCH v3 05/25] mm: Add put

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Message-ID: <61E16B01-4D4B-4ACA-A7C4-307CDABB3453@nvidia.com>
Date:   Mon, 1 Mar 2021 16:41:16 -0500
From:   Zi Yan <ziy@...dia.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
CC:     <linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 05/25] mm: Add put_folio

On 28 Jan 2021, at 2:03, Matthew Wilcox (Oracle) wrote:

> If we know we have a folio, we can call put_folio() instead of put_page()
> and save the overhead of calling compound_head().  Also skips the
> devmap checks.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  include/linux/mm.h | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7d787229dd40..873d649107ba 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1220,9 +1220,15 @@ static inline __must_check bool try_get_page(struct page *page)
>  	return true;
>  }
>
> +static inline void put_folio(struct folio *folio)
> +{
> +	if (put_page_testzero(&folio->page))
> +		__put_page(&folio->page);
> +}
> +
>  static inline void put_page(struct page *page)
>  {
> -	page = compound_head(page);
> +	struct folio *folio = page_folio(page);
>
>  	/*
>  	 * For devmap managed pages we need to catch refcount transition from
> @@ -1230,13 +1236,12 @@ static inline void put_page(struct page *page)
>  	 * need to inform the device driver through callback. See
>  	 * include/linux/memremap.h and HMM for details.
>  	 */
> -	if (page_is_devmap_managed(page)) {
> -		put_devmap_managed_page(page);
> +	if (page_is_devmap_managed(&folio->page)) {
> +		put_devmap_managed_page(&folio->page);
>  		return;
>  	}
>
> -	if (put_page_testzero(page))
> -		__put_page(page);
> +	put_folio(folio);
>  }
>
>  /*
> -- 
> 2.29.2

LGTM.

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


—
Best Regards,
Yan Zi

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