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Subject: Re: [RFC PATCH 1/9] include/linux/pagemap.h: introduce
 set/clear_fs_page_private
To:     Christoph Hellwig <hch@infradead.org>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        david@fromorbit.com, willy@infradead.org,
        Andrew Morton <akpm@linux-foundation.org>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        William Kucharski <william.kucharski@oracle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Yafang Shao <laoar.shao@gmail.com>
References: <20200426214925.10970-1-guoqing.jiang@cloud.ionos.com>
 <20200426214925.10970-2-guoqing.jiang@cloud.ionos.com>
 <20200427055255.GA16709@infradead.org>
From:   Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Message-ID: <125d6be2-eabb-16d1-19de-82c2e7de3851@cloud.ionos.com>
Date:   Mon, 27 Apr 2020 10:10:05 +0200
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Hi Christoph,

On 4/27/20 7:52 AM, Christoph Hellwig wrote:
> Why not attach_page_private and clear_page_private as that conveys
> the use case a little better?

Yes, thanks for the good suggestion. Will rename them if no one else
has new idea ...

>> +static inline void *set_fs_page_private(struct page *page, void *data)
>> +{
>> +	get_page(page);
>> +	set_page_private(page, (unsigned long)data);
>> +	SetPagePrivate(page);
>> +
>> +	return data;
>> +}
>> +
>> +static inline void *clear_fs_page_private(struct page *page)
>> +{
>> +	void *data = (void *)page_private(page);
>> +
>> +	if (!PagePrivate(page))
>> +		return NULL;
>> +	ClearPagePrivate(page);
>> +	set_page_private(page, 0);
>> +	put_page(page);
>> +
>> +	return data;
>> +}
> Can you add kerneldoc comments describing them, including why we
> take the refernces?

Ok, will do.

> Also what is the point of the return value of set_fs_page_private?

In this way, iomap_page_create can just return the function, but you
don't like this way as you replied, will change the return value to "void".

Thanks,
Guoqing