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Subject: Re: [RFC PATCH V2 1/9] include/linux/pagemap.h: introduce
 attach/clear_page_private
To:     Matthew Wilcox <willy@infradead.org>
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References: <20200430214450.10662-1-guoqing.jiang@cloud.ionos.com>
 <20200430214450.10662-2-guoqing.jiang@cloud.ionos.com>
 <20200430221338.GY29705@bombadil.infradead.org>
From:   Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Message-ID: <4c177757-7e27-420e-621b-98353ec43ea1@cloud.ionos.com>
Date:   Fri, 1 May 2020 08:39:31 +0200
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On 5/1/20 12:13 AM, Matthew Wilcox wrote:
> On Thu, Apr 30, 2020 at 11:44:42PM +0200, Guoqing Jiang wrote:
>> +/**
>> + * attach_page_private - attach data to page's private field and set PG_private.
>> + * @page: page to be attached and set flag.
>> + * @data: data to attach to page's private field.
>> + *
>> + * Need to take reference as mm.h said "Setting PG_private should also increment
>> + * the refcount".
>> + */
> I don't think this will read well when added to the API documentation.
> Try this:
>
> /**
>   * attach_page_private - Attach private data to a page.
>   * @page: Page to attach data to.
>   * @data: Data to attach to page.
>   *
>   * Attaching private data to a page increments the page's reference count.
>   * The data must be detached before the page will be freed.
>   */
>
>> +/**
>> + * clear_page_private - clear page's private field and PG_private.
>> + * @page: page to be cleared.
>> + *
>> + * The counterpart function of attach_page_private.
>> + * Return: private data of page or NULL if page doesn't have private data.
>> + */
> Seems to me that the opposite of "attach" is "detach", not "clear".
>
> /**
>   * detach_page_private - Detach private data from a page.
>   * @page: Page to detach data from.
>   *
>   * Removes the data that was previously attached to the page and decrements
>   * the refcount on the page.
>   *
>   * Return: Data that was attached to the page.
>   */

Thanks you very much, Mattew! Will change them in next version.

Best Regards,
Guoqing