Re: [RFC PATCH 3/9] btrfs: use set/clear_fs_page_private

[Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>]

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@xxxxxx>
> > Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
> > Cc: David Sterba <dsterba@xxxxxxxx>
> > Cc: linux-btrfs@xxxxxxxxxxxxxxx
> > Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
> ....
>
> >   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