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Subject: Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private
To:     Dave Chinner <david@fromorbit.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        hch@infradead.org, willy@infradead.org, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org
References: <20200426214925.10970-1-guoqing.jiang@cloud.ionos.com>
 <20200426214925.10970-4-guoqing.jiang@cloud.ionos.com>
 <20200426222054.GA2005@dread.disaster.area>
From:   Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Message-ID: <f0471728-6a03-3e44-f0cc-adb1a6bd3470@cloud.ionos.com>
Date:   Mon, 27 Apr 2020 10:14:17 +0200
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On 4/27/20 12:20 AM, Dave Chinner wrote:
> On Sun, Apr 26, 2020 at 11:49:19PM +0200, Guoqing Jiang wrote:
>> Since the new pair function is introduced, we can call them to clean the
>> code in btrfs.
>>
>> Cc: Chris Mason <clm@fb.com>
>> Cc: Josef Bacik <josef@toxicpanda.com>
>> Cc: David Sterba <dsterba@suse.com>
>> Cc: linux-btrfs@vger.kernel.org
>> Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
> ....
>
>>   void set_page_extent_mapped(struct page *page)
>>   {
>> -	if (!PagePrivate(page)) {
>> -		SetPagePrivate(page);
>> -		get_page(page);
>> -		set_page_private(page, EXTENT_PAGE_PRIVATE);
>> -	}
>> +	if (!PagePrivate(page))
>> +		set_fs_page_private(page, (void *)EXTENT_PAGE_PRIVATE);
> Change the definition of EXTENT_PAGE_PRIVATE so the cast is not
> needed? Nothing ever reads EXTENT_PAGE_PRIVATE; it's only there to
> set the private flag for other code to check and release the extent
> mapping reference to the page...

Not know the code well, so I just make the cast ...

>> @@ -8331,11 +8328,9 @@ static int btrfs_migratepage(struct address_space *mapping,
>>   
>>   	if (page_has_private(page)) {
>>   		ClearPagePrivate(page);
>> -		get_page(newpage);
>> -		set_page_private(newpage, page_private(page));
>> +		set_fs_page_private(newpage, (void *)page_private(page));
>>   		set_page_private(page, 0);
>>   		put_page(page);
>> -		SetPagePrivate(newpage);
>>   	}
> This is just:
> 		set_fs_page_private(newpage, clear_fs_page_private(page));
>

Thanks a lot! It is more better.

Thanks,
Guoqing