On Thu, Jul 11, 2024 at 10:50 AM Kundan Kumar <kundan.kumar@xxxxxxxxxxx> wrote:
>
> Using a helper function check if pages are contiguous and belong to same
> folio, this is done as a COW may happen and change contiguous mapping of
> pages of folio.
>
You can consider removing this part in the commit description, as the same
comment is present below in the code as well.
> #define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct page *))
>
> /**
> @@ -1298,9 +1329,9 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
> struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
> struct page **pages = (struct page **)bv;
> - ssize_t size, left;
> - unsigned len, i = 0;
> - size_t offset;
> + ssize_t size;
> + unsigned int i = 0, num_pages;
> + size_t offset, folio_offset, left, len;
> int ret = 0;
>
> /*
> @@ -1342,15 +1373,29 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>
> for (left = size, i = 0; left > 0; left -= len, i++) {
Can we do a i+=num_pages here, given that you are incrementing i by 1 here
and by (num_pages-1) at the end of the loop. This way you can get rid of
the increment that you are doing at the end of the loop.
> struct page *page = pages[i];
> + struct folio *folio = page_folio(page);
> +
> + folio_offset = ((size_t)folio_page_idx(folio, page) <<
> + PAGE_SHIFT) + offset;
> +
> + len = min_t(size_t, (folio_size(folio) - folio_offset), left);
> +
> + num_pages = DIV_ROUND_UP(offset + len, PAGE_SIZE);
> +
> + if (num_pages > 1)
> + len = get_contig_folio_len(&num_pages, pages, i,
> + folio, left, offset);
>
> - len = min_t(size_t, PAGE_SIZE - offset, left);
> if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
> - ret = bio_iov_add_zone_append_page(bio, page, len,
> - offset);
> + ret = bio_iov_add_zone_append_folio(bio, folio, len,
> + folio_offset);
> if (ret)
> break;
> } else
> - bio_iov_add_page(bio, page, len, offset);
> + bio_iov_add_folio(bio, folio, len, folio_offset);
> +
> + /* Skip the pages which got added */
> + i = i + (num_pages - 1);
>
> offset = 0;
> }
> --
> 2.25.1
>
--
Anuj Gupta
