Virtualization - Jun 2022 - [PATCH v2 12/19] btrfs: Convert btrfs_migratepage to migrate_folio

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 at infradead.org>
> Reviewed-by: Christoph Hellwig <hch at lst.de>
Acked-by: David Sterba <dsterba at 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.
> -
> -	if (PageOrdered(page)) {
> -		ClearPageOrdered(page);
> -		SetPageOrdered(newpage);
> +	if (folio_test_ordered(src)) {
> +		folio_clear_ordered(src);
> +		folio_set_ordered(dst);
>  	}

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 at infradead.org>
> > Reviewed-by: Christoph Hellwig <hch at lst.de>
> 
> Acked-by: David Sterba <dsterba at 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);
> >  	}