Re: [PATCH 10/10] mm/migrate.c: call detach_page_private to cleanup code

[Guoqing Jiang]

Hi Dave,

On 5/22/20 12:52 AM, Dave Chinner wrote:
> On Sun, May 17, 2020 at 11:47:18PM +0200, Guoqing Jiang wrote:
> > We can cleanup code a little by call detach_page_private here.
> >
> > Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
> > ---
> > No change since RFC V3.
> >
> >   mm/migrate.c | 5 +----
> >   1 file changed, 1 insertion(+), 4 deletions(-)
> >
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 5fed0305d2ec..f99502bc113c 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -804,10 +804,7 @@ static int __buffer_migrate_page(struct address_space *mapping,
> >   	if (rc != MIGRATEPAGE_SUCCESS)
> >   		goto unlock_buffers;
> >   
> > -	ClearPagePrivate(page);
> > -	set_page_private(newpage, page_private(page));
> > -	set_page_private(page, 0);
> > -	put_page(page);
> > +	set_page_private(newpage, detach_page_private(page));
> attach_page_private(newpage, detach_page_private(page));

Mattew had suggested it as follows, but not sure if we can reorder of 
the setup of
the bh and setting PagePrivate, so I didn't want to break the original 
syntax.

@@ -797,11 +797,7 @@ static int __buffer_migrate_page(struct address_space *mapping,
        if (rc != MIGRATEPAGE_SUCCESS)
                goto unlock_buffers;
 
-       ClearPagePrivate(page);
-       set_page_private(newpage, page_private(page));
-       set_page_private(page, 0);
-       put_page(page);
-       get_page(newpage);
+       attach_page_private(newpage, detach_page_private(page));
 
        bh = head;
        do {
@@ -810,8 +806,6 @@ static int __buffer_migrate_page(struct address_space *mapping,
 
        } while (bh != head);
 
-       SetPagePrivate(newpage);
-
        if (mode != MIGRATE_SYNC_NO_COPY)



[1]. 
https://lore.kernel.org/lkml/20200502004158.GD29705@xxxxxxxxxxxxxxxxxxxxxx/
[2]. 
https://lore.kernel.org/lkml/e4d5ddc0-877f-6499-f697-2b7c0ddbf386@xxxxxxxxxxxxxxx/

Thanks,
Guoqing