On Fri, Nov 11, 2016 at 8:05 PM, Ming Lei <tom.leiming@xxxxxxxxx> wrote:
> Firstly we have mature bvec/bio iterator helper for iterate each
> page in one bio, not necessary to reinvent a wheel to do that.
>
> Secondly the coming multipage bvecs requires this patch.
>
> Also add comments about the direct access to bvec table.
>
> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
> ---
> drivers/md/dm-io.c | 34 ++++++++++++++++++++++++----------
> 1 file changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
> index 0bf1a12e35fe..2ef573c220fc 100644
> --- a/drivers/md/dm-io.c
> +++ b/drivers/md/dm-io.c
> @@ -162,7 +162,10 @@ struct dpages {
> struct page **p, unsigned long *len, unsigned *offset);
> void (*next_page)(struct dpages *dp);
>
> - unsigned context_u;
> + union {
> + unsigned context_u;
> + struct bvec_iter context_bi;
> + };
> void *context_ptr;
>
> void *vma_invalidate_address;
> @@ -204,25 +207,36 @@ static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offse
> static void bio_get_page(struct dpages *dp, struct page **p,
> unsigned long *len, unsigned *offset)
> {
> - struct bio_vec *bvec = dp->context_ptr;
> - *p = bvec->bv_page;
> - *len = bvec->bv_len - dp->context_u;
> - *offset = bvec->bv_offset + dp->context_u;
> + struct bio_vec bv = bvec_iter_bvec((struct bio_vec *)dp->context_ptr,
> + dp->context_bi);
> +
> + *p = bv.bv_page;
> + *len = bv.bv_len;
> + *offset = bv.bv_offset;
> +
> + /* avoid to figure out it in bio_next_page() again */
> + dp->context_bi.bi_sector = (sector_t)bv.bv_len;
> }
>
> static void bio_next_page(struct dpages *dp)
> {
> - struct bio_vec *bvec = dp->context_ptr;
> - dp->context_ptr = bvec + 1;
> - dp->context_u = 0;
> + unsigned int len = (unsigned int)dp->context_bi.bi_sector;
> +
> + bvec_iter_advance((struct bio_vec *)dp->context_ptr,
> + &dp->context_bi, len);
> }
>
> static void bio_dp_init(struct dpages *dp, struct bio *bio)
> {
> dp->get_page = bio_get_page;
> dp->next_page = bio_next_page;
> - dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
> - dp->context_u = bio->bi_iter.bi_bvec_done;
> +
> + /*
> + * We just use bvec iterator to retrieve pages, so it is ok to
> + * access the bvec table directly here
> + */
> + dp->context_ptr = bio->bi_io_vec;
> + dp->context_bi = bio->bi_iter;
> }
Hi Alasdair, Mike, Christoph and anyone,
Could you give this one a review?
>From my test, it just works fine, and I believe it is a good cleanup.
Thanks,
Ming Lei
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