On Mon, Jan 23, 2023 at 05:30:07PM +0000, David Howells wrote:

Renumber FOLL_PIN and FOLL_GET down to bit 0 and 1 respectively so that
they are coincidentally the same as BIO_PAGE_PINNED and BIO_PAGE_REFFED and
also so that they can be stored in the bottom two bits of a page pointer
(something I'm looking at for zerocopy socket fragments).

(Note that BIO_PAGE_REFFED should probably be got rid of at some point,
hence why FOLL_PIN is at 0.)

Also renumber down the other FOLL_* flags to close the gaps.

Taking the risk of having a long bikeshed:  I much prefer (1U << bitnr)
style definition that make it obvious where there are holes, but
otherwise:

Reviewed-by: Christoph Hellwig <hch@lst.de>