linux-kernel - Re: [PATCH v14 001/138] mm: Convert get_page_unless

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Date:   Tue, 10 Aug 2021 17:50:35 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v14 001/138] mm: Convert get_page_unless_zero() to return
 bool

On 7/15/21 5:34 AM, Matthew Wilcox (Oracle) wrote:
> atomic_add_unless() returns bool, so remove the widening casts to int
> in page_ref_add_unless() and get_page_unless_zero().  This causes gcc
> to produce slightly larger code in isolate_migratepages_block(), but
> it's not clear that it's worse code.  Net +19 bytes of text.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  include/linux/mm.h       | 2 +-
>  include/linux/page_ref.h | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7ca22e6e694a..8dd65290bac0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -755,7 +755,7 @@ static inline int put_page_testzero(struct page *page)
>   * This can be called when MMU is off so it must not access
>   * any of the virtual mappings.
>   */
> -static inline int get_page_unless_zero(struct page *page)
> +static inline bool get_page_unless_zero(struct page *page)
>  {
>  	return page_ref_add_unless(page, 1, 0);
>  }
> diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h
> index 7ad46f45df39..3a799de8ad52 100644
> --- a/include/linux/page_ref.h
> +++ b/include/linux/page_ref.h
> @@ -161,9 +161,9 @@ static inline int page_ref_dec_return(struct page *page)
>  	return ret;
>  }
>  
> -static inline int page_ref_add_unless(struct page *page, int nr, int u)
> +static inline bool page_ref_add_unless(struct page *page, int nr, int u)
>  {
> -	int ret = atomic_add_unless(&page->_refcount, nr, u);
> +	bool ret = atomic_add_unless(&page->_refcount, nr, u);
>  
>  	if (page_ref_tracepoint_active(page_ref_mod_unless))
>  		__page_ref_mod_unless(page, nr, ret);
>