Re: [PATCH v6 11/34] iov_iter, block: Make bio structs pin pages rather than ref'ing if appropriate

[Christoph Hellwig]

On Tue, Jan 17, 2023 at 08:26:08AM +0000, David Howells wrote:
> Um... With these patches, BIO_PAGE_REFFED is set by default when the bio is
> initialised otherwise every user of struct bio that currently adds pages
> directly (assuming there are any) rather than going through
> bio_iov_iter_get_pages() will have to set the flag, hence the need to clear
> it.

I think we need to fix that (in the patch inverting the polarity) and
only set the flag where it is needed.

All eventually calls come from the direct I/O code in the block layer,
iomap, legacy generic and zonefs, and they release pages that came
from some form of hup.  So we can just set BIO_PAGE_REFFED in
bio_iov_iter_get_pages and dio_refill_pages.