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SubjectRe: [PATCH 3/9] virtio-blk: use virtqueue_start_buf on bio path
On 02/12/2013 08:23 PM, Paolo Bonzini wrote:
> Move the creation of the request header and response footer to
> __virtblk_add_req. vbr->sg only contains the data scatterlist,
> the header/footer are added separately using the new piecewise
> API for building virtqueue buffers.
>
> With this change, virtio-blk (with use_bio) is not relying anymore on
> the virtio functions ignoring the end markers in a scatterlist.
> The next patch will do the same for the other path.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Asias He <asias@redhat.com>

> ---
> drivers/block/virtio_blk.c | 74 ++++++++++++++++++++++++++-----------------
> 1 files changed, 45 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index fd8a689..4a31fcc 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -62,6 +62,7 @@ struct virtblk_req
> struct virtio_blk *vblk;
> int flags;
> u8 status;
> + int nents;
> struct scatterlist sg[];
> };
>
> @@ -100,24 +101,52 @@ static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
> return vbr;
> }
>
> -static inline int __virtblk_add_req(struct virtqueue *vq,
> - struct virtblk_req *vbr,
> - unsigned long out,
> - unsigned long in)
> +static int __virtblk_add_req(struct virtqueue *vq,
> + struct virtblk_req *vbr)
> {
> - return virtqueue_add_buf(vq, vbr->sg, out, in, vbr, GFP_ATOMIC);
> + struct scatterlist sg;
> + enum dma_data_direction dir;
> + int ret;
> +
> + unsigned int nents = 2;
> + unsigned int nsg = 2;
> +
> + if (vbr->nents) {
> + nsg++;
> + nents += vbr->nents;
> + }
> +
> + ret = virtqueue_start_buf(vq, vbr, nents, nsg, GFP_ATOMIC);
> + if (ret < 0)
> + return ret;
> +
> + dir = DMA_TO_DEVICE;
> + sg_init_one(&sg, &vbr->out_hdr, sizeof(vbr->out_hdr));
> + virtqueue_add_sg(vq, &sg, 1, dir);
> +
> + if (vbr->nents) {
> + if ((vbr->out_hdr.type & VIRTIO_BLK_T_OUT) == 0)
> + dir = DMA_FROM_DEVICE;
> +
> + virtqueue_add_sg(vq, vbr->sg, vbr->nents, dir);
> + }
> +
> + dir = DMA_FROM_DEVICE;
> + sg_init_one(&sg, &vbr->status, sizeof(vbr->status));
> + virtqueue_add_sg(vq, &sg, 1, dir);
> +
> + virtqueue_end_buf(vq);
> + return 0;
> }
>
> -static void virtblk_add_req(struct virtblk_req *vbr,
> - unsigned int out, unsigned int in)
> +static void virtblk_add_req(struct virtblk_req *vbr)
> {
> struct virtio_blk *vblk = vbr->vblk;
> DEFINE_WAIT(wait);
> int ret;
>
> spin_lock_irq(vblk->disk->queue->queue_lock);
> - while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr,
> - out, in)) < 0)) {
> + while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr)) < 0)) {
> prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
> TASK_UNINTERRUPTIBLE);
>
> @@ -134,22 +163,18 @@ static void virtblk_add_req(struct virtblk_req *vbr,
>
> static void virtblk_bio_send_flush(struct virtblk_req *vbr)
> {
> - unsigned int out = 0, in = 0;
> -
> vbr->flags |= VBLK_IS_FLUSH;
> vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
> vbr->out_hdr.sector = 0;
> vbr->out_hdr.ioprio = 0;
> - sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
> - sg_set_buf(&vbr->sg[out + in++], &vbr->status, sizeof(vbr->status));
> + vbr->nents = 0;
>
> - virtblk_add_req(vbr, out, in);
> + virtblk_add_req(vbr);
> }
>
> static void virtblk_bio_send_data(struct virtblk_req *vbr)
> {
> struct virtio_blk *vblk = vbr->vblk;
> - unsigned int num, out = 0, in = 0;
> struct bio *bio = vbr->bio;
>
> vbr->flags &= ~VBLK_IS_FLUSH;
> @@ -157,24 +182,15 @@ static void virtblk_bio_send_data(struct virtblk_req *vbr)
> vbr->out_hdr.sector = bio->bi_sector;
> vbr->out_hdr.ioprio = bio_prio(bio);
>
> - sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
> -
> - num = blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg + out);
> -
> - sg_set_buf(&vbr->sg[num + out + in++], &vbr->status,
> - sizeof(vbr->status));
> -
> - if (num) {
> - if (bio->bi_rw & REQ_WRITE) {
> + vbr->nents = blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg);
> + if (vbr->nents) {
> + if (bio->bi_rw & REQ_WRITE)
> vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
> - out += num;
> - } else {
> + else
> vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
> - in += num;
> - }
> }
>
> - virtblk_add_req(vbr, out, in);
> + virtblk_add_req(vbr);
> }
>
> static void virtblk_bio_send_data_work(struct work_struct *work)
>


--
Asias


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