Re: RFA (Request for Advice): block/bio: get_user_pages() --> pin_user_pages()

[Jan Kara <jack@suse.cz>]

On Mon 24-01-22 11:34:25, John Hubbard wrote:
> On 1/24/22 04:19, Jan Kara wrote:
> > > address for each ZERO_PAGE() (unless I'm totally wrong here) and
> > > using this check you can distinguish between ZERO_PAGE() and
> > > non ZERO_PAGE() on the bio list in bio_release_pages().
> > 
> > Well, that is another option but it seems a bit ugly and also on some
> > architectures (e.g. s390 AFAICS) there can be multiple zero pages (due to
> > coloring) so the test for zero page is not completely trivial (probably we
> > would have to grow some is_zero_page() checking function implemented
> > separately for each arch).
> 
> Good point. And adding an is_zero_page() function would also make some
> of these invocations correct across all architectures:
> 
>     is_zero_pfn(page_to_pfn(page))
> 
> ...so it would also be a fix or at least an upgrade.

As I'm checking the is_zero_pfn() implementation, it should be working as it
should for all architectures. I just forgot we already have a function for
this.

> I had also wondered why there is no is_zero_page() wrapper function for
> the above invocation. Maybe because there are only four call sites and
> no one saw it as worthwhile yet.

Yeah, perhaps.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR