Re: [PATCH v2 0/7] convert most filesystems to pin_user_pages_fast()

[Christoph Hellwig]

On Tue, Sep 06, 2022 at 12:10:54AM -0700, John Hubbard wrote:
> I would be delighted if that were somehow possible. Every time I think
> it's possible, it has fallen apart. The fact that bio_release_pages()
> will need to switch over from put_page() to unpin_user_page(), combined
> with the fact that there are a lot of callers that submit bios, has
> led me to the current approach.

We can (temporarily) pass the gup flag to bio_release_pages or even
better add a new bio_unpin_pages helper that undoes the pin side.
That is: don't try to reuse the old APIs, but ad new ones, just like
we do on the lower layers.