On Sat, Nov 10, 2018 at 12:29 AM Ming Lei <ming.lei@xxxxxxxxxx> wrote:
>
> This patch pulls the trigger for multi-page bvecs.
>
> Now any request queue which supports queue cluster will see multi-page
> bvecs.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> block/bio.c | 23 +++++++++++++++++------
> 1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 6486722d4d4b..b2ce42e89076 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -767,12 +767,23 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
>
> if (bio->bi_vcnt > 0) {
> struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
> -
> - if (page == bv->bv_page && off == bv->bv_offset + bv->bv_len) {
> - bv->bv_len += len;
> - bio->bi_iter.bi_size += len;
> - return true;
> - }
> + struct request_queue *q = NULL;
> +
> + if (page == bv->bv_page && off == bv->bv_offset + bv->bv_len)
> + goto merge;
> +
> + if (bio->bi_disk)
> + q = bio->bi_disk->queue;
> +
> + /* disable multi-page bvec too if cluster isn't enabled */
> + if (!q || !blk_queue_cluster(q) ||
> + (page_to_phys(bv->bv_page) + bv->bv_offset + bv->bv_len !=
> + page_to_phys(page) + off))
> + return false;
> + merge:
> + bv->bv_len += len;
> + bio->bi_iter.bi_size += len;
> + return true;
> }
> return false;
> }
This patch caused regression on iomap & xfs for sub-pagesize io vec, which
has been addressed in the following patch:
https://github.com/ming1/linux/commit/46ea6acb175fbc68f98f645f14d77b1b4178e593
Because iomap needs to know if the merged page is one freshly new page, however
__bio_try_merge_page() won't tell us if that is true.
I will post out V9 once the new change passes my tests.
Thanks,
Ming Lei
