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

[David Howells]

Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

> > +	bio_clear_flag(bio, BIO_PAGE_REFFED);
> 
> .. and this should not be needed.  Instead:
> 
> > +	cleanup_mode = iov_iter_extract_mode(iter, gup_flags);
> > +	if (cleanup_mode & FOLL_GET)
> > +		bio_set_flag(bio, BIO_PAGE_REFFED);
> > +	if (cleanup_mode & FOLL_PIN)
> > +		bio_set_flag(bio, BIO_PAGE_PINNED);
> 
> We could warn if a not match flag is set here if we really care.

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.

Actually, I could do:

	if (!(cleanup_mode & FOLL_GET))
		bio_clear_flag(bio, BIO_PAGE_REFFED);
	if (cleanup_mode & FOLL_PIN)
		bio_set_flag(bio, BIO_PAGE_PINNED);

which should also work.

David