On Fri, Oct 27, 2023 at 05:41:10PM +0200, Pankaj Raghav wrote:
> On 27/10/2023 12:47, Matthew Wilcox wrote:
> > On Fri, Oct 27, 2023 at 10:03:15AM +0200, Pankaj Raghav wrote:
> >> I also noticed this pattern in fscrypt_zeroout_range_inline_crypt().
> >> Probably there are more places which could use a ZERO_FOLIO directly
> >> instead of iterating with ZERO_PAGE.
> >>
> >> Chinner also had a similar comment. It would be nice if we can reserve
> >> a zero huge page that is the size of MAX_PAGECACHE_ORDER and add it as
> >> one folio to the bio.
> >
> > i'm on holiday atm. start looking at mm_get_huge_zero_page()
>
> Thanks for the pointer. I made a rough version of how it might
> look like if I use that API:
useful thing to do. i think this shows we need a new folio api wrapping
it. happy to do that when i'm back, or you can have a crack at it.
your point about it possibly failing is correct. so i think we need an
api which definitely returns a folio, but it might be of arbitrary
order.
> bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
> bio->bi_private = dio;
> bio->bi_end_io = iomap_dio_bio_end_io;
>
> - __bio_add_page(bio, page, len, 0);
> + if (!fallback) {
> + bio_add_folio_nofail(bio, page_folio(page), len, 0);
> + } else {
> + while (len) {
> + unsigned int io_len =
> + min_t(unsigned int, len, PAGE_SIZE);
> +
> + __bio_add_page(bio, page, io_len, 0);
> + len -= io_len;
> + }
> + }
> +
> iomap_dio_submit_bio(iter, dio, bio, pos);
then this can look something like:
while (len) {
size_t size = min(len, folio_size(folio));
__bio_add_folio(bio, folio, size, 0);
len -= size;
}
> PS: Enjoy your holidays :)
cheers ;-)
