Re: [PATCH 6/8] Direct Migration V2: Avoid writeback / page_migrate() method

Christoph Lameter
2005-11-09T17:07:36Z

On Wed, 9 Nov 2005, Nikita Danilov wrote:

> > +#ifdef CONFIG_MIGRATION
> > +extern int buffer_migrate_page(struct page *, struct page *);
> > +#else
> > +#define buffer_migrate_page(a,b) NULL
> > +#endif
>
> Depending on the CONFIG_MIGRATION, the type of buffer_migrate_page(a,b)
> expansion is either int or void *, which doesn't look right.

But its right. You need to think about buffer_migrate_page as a pointer to
a function.

> Moreover below you have initializations
>
> .migrate_page = buffer_migrate_page,
>
> that wouldn't compile when CONFIG_MIGRATION is not defined (as macro
> requires two arguments).

NULL is a void * pointer which should work.