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Date: Wed, 20 Feb 2013 18:09:19 +0800
From: Wanlong Gao <gaowanlong@...fujitsu.com>
To: Rusty Russell <rusty@...tcorp.com.au>
CC: Paolo Bonzini <pbonzini@...hat.com>,
virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH 07/16] virtio_ring: don't count elements twice for add_buf
path.
On 02/19/2013 03:56 PM, Rusty Russell wrote:
> Extract the post-counting code into virtqueue_add(), make both callers
> use it.
>
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Reviewed-by: Wanlong Gao <gaowanlong@...fujitsu.com>
> ---
> drivers/virtio/virtio_ring.c | 147 +++++++++++++++++++++++-------------------
> 1 file changed, 80 insertions(+), 67 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 27e31d3..c537385 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -163,69 +163,17 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
> return head;
> }
>
> -/**
> - * virtqueue_add_buf - expose buffer to other end
> - * @vq: the struct virtqueue we're talking about.
> - * @sg: the description of the buffer(s).
> - * @out_num: the number of sg readable by other side
> - * @in_num: the number of sg which are writable (after readable ones)
> - * @data: the token identifying the buffer.
> - * @gfp: how to do memory allocations (if necessary).
> - *
> - * Caller must ensure we don't call this with other virtqueue operations
> - * at the same time (except where noted).
> - *
> - * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
> - */
> -int virtqueue_add_buf(struct virtqueue *_vq,
> - struct scatterlist sg[],
> - unsigned int out,
> - unsigned int in,
> - void *data,
> - gfp_t gfp)
> -{
> - struct scatterlist *sgs[2];
> - unsigned int i;
> -
> - sgs[0] = sg;
> - sgs[1] = sg + out;
> -
> - /* Workaround until callers pass well-formed sgs. */
> - for (i = 0; i < out + in; i++)
> - sg_unmark_end(sg + i);
> -
> - sg_mark_end(sg + out + in - 1);
> - if (out && in)
> - sg_mark_end(sg + out - 1);
> -
> - return virtqueue_add_sgs(_vq, sgs, out ? 1 : 0, in ? 1 : 0, data, gfp);
> -}
> -EXPORT_SYMBOL_GPL(virtqueue_add_buf);
> -
> -/**
> - * virtqueue_add_sgs - expose buffers to other end
> - * @vq: the struct virtqueue we're talking about.
> - * @sgs: array of terminated scatterlists.
> - * @out_num: the number of scatterlists readable by other side
> - * @in_num: the number of scatterlists which are writable (after readable ones)
> - * @data: the token identifying the buffer.
> - * @gfp: how to do memory allocations (if necessary).
> - *
> - * Caller must ensure we don't call this with other virtqueue operations
> - * at the same time (except where noted).
> - *
> - * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
> - */
> -int virtqueue_add_sgs(struct virtqueue *_vq,
> - struct scatterlist *sgs[],
> - unsigned int out_sgs,
> - unsigned int in_sgs,
> - void *data,
> - gfp_t gfp)
> +static int virtqueue_add(struct virtqueue *_vq,
> + struct scatterlist *sgs[],
> + unsigned int total_sg,
> + unsigned int out_sgs,
> + unsigned int in_sgs,
> + void *data,
> + gfp_t gfp)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> struct scatterlist *sg;
> - unsigned int i, n, avail, uninitialized_var(prev), total_sg;
> + unsigned int i, n, avail, uninitialized_var(prev);
> int head;
>
> START_USE(vq);
> @@ -245,13 +193,6 @@ int virtqueue_add_sgs(struct virtqueue *_vq,
> }
> #endif
>
> - /* Count them first. */
> - for (i = total_sg = 0; i < out_sgs + in_sgs; i++) {
> - struct scatterlist *sg;
> - for (sg = sgs[i]; sg; sg = sg_next(sg))
> - total_sg++;
> - }
> -
> /* If the host supports indirect descriptor tables, and we have multiple
> * buffers, then go indirect. FIXME: tune this threshold */
> if (vq->indirect && total_sg > 1 && vq->vq.num_free) {
> @@ -329,6 +270,78 @@ add_head:
>
> return 0;
> }
> +
> +/**
> + * virtqueue_add_buf - expose buffer to other end
> + * @vq: the struct virtqueue we're talking about.
> + * @sg: the description of the buffer(s).
> + * @out_num: the number of sg readable by other side
> + * @in_num: the number of sg which are writable (after readable ones)
> + * @data: the token identifying the buffer.
> + * @gfp: how to do memory allocations (if necessary).
> + *
> + * Caller must ensure we don't call this with other virtqueue operations
> + * at the same time (except where noted).
> + *
> + * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
> + */
> +int virtqueue_add_buf(struct virtqueue *_vq,
> + struct scatterlist sg[],
> + unsigned int out,
> + unsigned int in,
> + void *data,
> + gfp_t gfp)
> +{
> + struct scatterlist *sgs[2];
> + unsigned int i;
> +
> + sgs[0] = sg;
> + sgs[1] = sg + out;
> +
> + /* Workaround until callers pass well-formed sgs. */
> + for (i = 0; i < out + in; i++)
> + sg_unmark_end(sg + i);
> +
> + sg_mark_end(sg + out + in - 1);
> + if (out && in)
> + sg_mark_end(sg + out - 1);
> +
> + return virtqueue_add(_vq, sgs, out+in, out ? 1 : 0, in ? 1 : 0,
> + data, gfp);
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_add_buf);
> +
> +/**
> + * virtqueue_add_sgs - expose buffers to other end
> + * @vq: the struct virtqueue we're talking about.
> + * @sgs: array of terminated scatterlists.
> + * @out_num: the number of scatterlists readable by other side
> + * @in_num: the number of scatterlists which are writable (after readable ones)
> + * @data: the token identifying the buffer.
> + * @gfp: how to do memory allocations (if necessary).
> + *
> + * Caller must ensure we don't call this with other virtqueue operations
> + * at the same time (except where noted).
> + *
> + * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
> + */
> +int virtqueue_add_sgs(struct virtqueue *_vq,
> + struct scatterlist *sgs[],
> + unsigned int out_sgs,
> + unsigned int in_sgs,
> + void *data,
> + gfp_t gfp)
> +{
> + unsigned int i, total_sg;
> +
> + /* Count them first. */
> + for (i = total_sg = 0; i < out_sgs + in_sgs; i++) {
> + struct scatterlist *sg;
> + for (sg = sgs[i]; sg; sg = sg_next(sg))
> + total_sg++;
> + }
> + return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);
> +}
> EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
>
> /**
>
--
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