Re: [PATCH v2 11/51] md: raid1: initialize bvec table via bio_add_page()

Guoqing Jiang
2017-06-27T09:36:59Z

On 06/26/2017 08:09 PM, Ming Lei wrote:
> We will support multipage bvec soon, so initialize bvec
> table using the standardy way instead of writing the
> talbe directly. Otherwise it won't work any more once
> multipage bvec is enabled.
>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: linux-raid@vger.kernel.org
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> drivers/md/raid1.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 3febfc8391fb..835c42396861 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -2086,10 +2086,8 @@ static void process_checks(struct r1bio *r1_bio)
> /* Fix variable parts of all bios */
> vcnt = (r1_bio->sectors + PAGE_SIZE / 512 - 1) >> (PAGE_SHIFT - 9);
> for (i = 0; i < conf->raid_disks * 2; i++) {
> - int j;
> int size;
> blk_status_t status;
> - struct bio_vec *bi;
> struct bio *b = r1_bio->bios[i];
> struct resync_pages *rp = get_resync_pages(b);
> if (b->bi_end_io != end_sync_read)
> @@ -2098,8 +2096,6 @@ static void process_checks(struct r1bio *r1_bio)
> status = b->bi_status;
> bio_reset(b);
> b->bi_status = status;
> - b->bi_vcnt = vcnt;
> - b->bi_iter.bi_size = r1_bio->sectors << 9;
> b->bi_iter.bi_sector = r1_bio->sector +
> conf->mirrors[i].rdev->data_offset;
> b->bi_bdev = conf->mirrors[i].rdev->bdev;
> @@ -2107,15 +2103,20 @@ static void process_checks(struct r1bio *r1_bio)
> rp->raid_bio = r1_bio;
> b->bi_private = rp;
>
> - size = b->bi_iter.bi_size;
> - bio_for_each_segment_all(bi, b, j) {
> - bi->bv_offset = 0;
> - if (size > PAGE_SIZE)
> - bi->bv_len = PAGE_SIZE;
> - else
> - bi->bv_len = size;
> - size -= PAGE_SIZE;
> - }
> + /* initialize bvec table again */
> + rp->idx = 0;
> + size = r1_bio->sectors << 9;
> + do {
> + struct page *page = resync_fetch_page(rp, rp->idx++);
> + int len = min_t(int, size, PAGE_SIZE);
> +
> + /*
> + * won't fail because the vec table is big
> + * enough to hold all these pages
> + */
> + bio_add_page(b, page, len, 0);
> + size -= len;
> + } while (rp->idx < RESYNC_PAGES && size > 0);
> }

Seems above section is similar as reset_bvec_table introduced in next patch,
why there is difference between raid1 and raid10? Maybe add reset_bvec_table
into md.c, then call it in raid1 or raid10 is better, just my 2 cents.

Thanks,
Guoqing