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Date:   Sun, 26 Apr 2020 22:54:28 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Guoqing Jiang <guoqing.jiang@cloud.ionos.com>,
        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
Subject: Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private
Message-ID: <20200427055428.GB16709@infradead.org>
References: <20200426214925.10970-1-guoqing.jiang@cloud.ionos.com>
 <20200426214925.10970-4-guoqing.jiang@cloud.ionos.com>
 <20200426222054.GA2005@dread.disaster.area>
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On Mon, Apr 27, 2020 at 08:20:54AM +1000, Dave Chinner wrote:
> >  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...

IIRC there as a patch on the btrfs list to remove EXTENT_PAGE_PRIVATE,
it might be better to not bother changing it.  Maybe the btrfs
maintainers remember this better.