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Date:   Thu, 9 Jun 2022 18:40:28 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     dsterba@suse.cz, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-aio@kvack.org, linux-btrfs@vger.kernel.org,
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        linux-xfs@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-ntfs-dev@lists.sourceforge.net, ocfs2-devel@oss.oracle.com,
        linux-mtd@lists.infradead.org,
        virtualization@lists.linux-foundation.org,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2 12/19] btrfs: Convert btrfs_migratepage to
 migrate_folio
Message-ID: <YqIwjEO1a0Sbxbym@casper.infradead.org>
References: <20220608150249.3033815-1-willy@infradead.org>
 <20220608150249.3033815-13-willy@infradead.org>
 <20220609163323.GV20633@twin.jikos.cz>
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On Thu, Jun 09, 2022 at 06:33:23PM +0200, David Sterba wrote:
> On Wed, Jun 08, 2022 at 04:02:42PM +0100, Matthew Wilcox (Oracle) wrote:
> > Use filemap_migrate_folio() to do the bulk of the work, and then copy
> > the ordered flag across if needed.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Acked-by: David Sterba <dsterba@suse.com>
> 
> > +static int btrfs_migrate_folio(struct address_space *mapping,
> > +			     struct folio *dst, struct folio *src,
> >  			     enum migrate_mode mode)
> >  {
> > -	int ret;
> > +	int ret = filemap_migrate_folio(mapping, dst, src, mode);
> >  
> > -	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
> >  	if (ret != MIGRATEPAGE_SUCCESS)
> >  		return ret;
> >  
> > -	if (page_has_private(page))
> > -		attach_page_private(newpage, detach_page_private(page));
> 
> If I'm reading it correctly, the private pointer does not need to be set
> like that anymore because it's done somewhere during the
> filemap_migrate_folio() call.

That's correct.  Everything except moving the ordered flag across is
done for you, and I'm kind of tempted to modify folio_migrate_flags()
to copy the ordered flag across as well.  Then you could just use
filemap_migrate_folio() directly.

> > -
> > -	if (PageOrdered(page)) {
> > -		ClearPageOrdered(page);
> > -		SetPageOrdered(newpage);
> > +	if (folio_test_ordered(src)) {
> > +		folio_clear_ordered(src);
> > +		folio_set_ordered(dst);
> >  	}