linux-kernel - Re: [PATCH 1/8] xen/grant-table: Make set/clear page private code shared

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Message-ID: <20180530213416.GA3159@downor-Z87X-UD5H>
Date:   Wed, 30 May 2018 14:34:16 -0700
From:   Dongwon Kim <dongwon.kim@...el.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        jgross@...e.com, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com, daniel.vetter@...el.com,
        matthew.d.roper@...el.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH 1/8] xen/grant-table: Make set/clear page private code
 shared

On Fri, May 25, 2018 at 06:33:24PM +0300, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> 
> Make set/clear page private code shared and accessible to
> other kernel modules which can re-use these instead of open-coding.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> ---
>  drivers/xen/grant-table.c | 54 +++++++++++++++++++++++++--------------
>  include/xen/grant_table.h |  3 +++
>  2 files changed, 38 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 27be107d6480..d7488226e1f2 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -769,29 +769,18 @@ void gnttab_free_auto_xlat_frames(void)
>  }
>  EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);
>  
> -/**
> - * gnttab_alloc_pages - alloc pages suitable for grant mapping into
> - * @nr_pages: number of pages to alloc
> - * @pages: returns the pages
> - */
> -int gnttab_alloc_pages(int nr_pages, struct page **pages)
> +int gnttab_pages_set_private(int nr_pages, struct page **pages)
>  {
>  	int i;
> -	int ret;
> -
> -	ret = alloc_xenballooned_pages(nr_pages, pages);
> -	if (ret < 0)
> -		return ret;
>  
>  	for (i = 0; i < nr_pages; i++) {
>  #if BITS_PER_LONG < 64
>  		struct xen_page_foreign *foreign;
>  
>  		foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
> -		if (!foreign) {
> -			gnttab_free_pages(nr_pages, pages);
> +		if (!foreign)

Don't we have to free previously allocated "foreign"(s) if it fails in the middle
(e.g. 0 < i && i < nr_pages - 1) before returning?

>  			return -ENOMEM;
> -		}
> +
>  		set_page_private(pages[i], (unsigned long)foreign);
>  #endif
>  		SetPagePrivate(pages[i]);
> @@ -799,14 +788,30 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
>  
>  	return 0;
>  }
> -EXPORT_SYMBOL(gnttab_alloc_pages);
> +EXPORT_SYMBOL(gnttab_pages_set_private);
>  
>  /**
> - * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
> - * @nr_pages; number of pages to free
> - * @pages: the pages
> + * gnttab_alloc_pages - alloc pages suitable for grant mapping into
> + * @nr_pages: number of pages to alloc
> + * @pages: returns the pages
>   */
> -void gnttab_free_pages(int nr_pages, struct page **pages)
> +int gnttab_alloc_pages(int nr_pages, struct page **pages)
> +{
> +	int ret;
> +
> +	ret = alloc_xenballooned_pages(nr_pages, pages);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = gnttab_pages_set_private(nr_pages, pages);
> +	if (ret < 0)
> +		gnttab_free_pages(nr_pages, pages);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(gnttab_alloc_pages);
> +
> +void gnttab_pages_clear_private(int nr_pages, struct page **pages)
>  {
>  	int i;
>  
> @@ -818,6 +823,17 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
>  			ClearPagePrivate(pages[i]);
>  		}
>  	}
> +}
> +EXPORT_SYMBOL(gnttab_pages_clear_private);
> +
> +/**
> + * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
> + * @nr_pages; number of pages to free
> + * @pages: the pages
> + */
> +void gnttab_free_pages(int nr_pages, struct page **pages)
> +{
> +	gnttab_pages_clear_private(nr_pages, pages);
>  	free_xenballooned_pages(nr_pages, pages);
>  }
>  EXPORT_SYMBOL(gnttab_free_pages);
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 2e37741f6b8d..de03f2542bb7 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -198,6 +198,9 @@ void gnttab_free_auto_xlat_frames(void);
>  int gnttab_alloc_pages(int nr_pages, struct page **pages);
>  void gnttab_free_pages(int nr_pages, struct page **pages);
>  
> +int gnttab_pages_set_private(int nr_pages, struct page **pages);
> +void gnttab_pages_clear_private(int nr_pages, struct page **pages);
> +
>  int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
>  		    struct gnttab_map_grant_ref *kmap_ops,
>  		    struct page **pages, unsigned int count);
> -- 
> 2.17.0
>