On Thu, Dec 17, 2009 at 11:43:50PM -0800, Shirley Ma wrote:
> There's currently no way for a virtio driver to ask for unused
> buffers, so it has to keep a list itself to reclaim them at shutdown.
> This is redundant, since virtio_ring stores that information. So
> add a new hook to do this: virtio_net will be the first user.
>
> Signed-off-by: Shirley Ma <x...@us.ibm.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> drivers/virtio/virtio_ring.c | 25 +++++++++++++++++++++++++
> include/linux/virtio.h | 4 ++++
> 2 files changed, 29 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index fbd2ecd..71929ee 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -334,6 +334,30 @@ static bool vring_enable_cb(struct virtqueue *_vq)
> return true;
> }
>
> +static void *vring_detach_unused_buf(struct virtqueue *_vq)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + unsigned int i;
> + void *buf;
> +
> + START_USE(vq);
> +
> + for (i = 0; i < vq->vring.num; i++) {
> + if (!vq->data[i])
> + continue;
> + /* detach_buf clears data, so grab it now. */
> + buf = vq->data[i];
> + detach_buf(vq, i);
> + END_USE(vq);
> + return buf;
> + }
> + /* That should have freed everything. */
> + BUG_ON(vq->num_free != vq->vring.num);
> +
> + END_USE(vq);
> + return NULL;
> +}
> +
> irqreturn_t vring_interrupt(int irq, void *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> @@ -360,6 +384,7 @@ static struct virtqueue_ops vring_vq_ops = {
> .kick = vring_kick,
> .disable_cb = vring_disable_cb,
> .enable_cb = vring_enable_cb,
> + .detach_unused_buf = vring_detach_unused_buf,
> };
>
> struct virtqueue *vring_new_virtqueue(unsigned int num,
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 057a2e0..f508c65 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -51,6 +51,9 @@ struct virtqueue {
> * This re-enables callbacks; it returns "false" if there are pending
> * buffers in the queue, to detect a possible race between the driver
> * checking for more work, and enabling callbacks.
> + * @detach_unused_buf: detach first unused buffer
> + * vq: the struct virtqueue we're talking about.
> + * Returns NULL or the "data" token handed to add_buf
> *
> * Locking rules are straightforward: the driver is responsible for
> * locking. No two operations may be invoked simultaneously, with the
> exception
> @@ -71,6 +74,7 @@ struct virtqueue_ops {
>
> void (*disable_cb)(struct virtqueue *vq);
> bool (*enable_cb)(struct virtqueue *vq);
> + void *(*detach_unused_buf)(struct virtqueue *vq);
> };
>
> /**
>
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