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virtio: Add ability to detach unused buffers from vrings 

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.

Signed-off-by: Shirley Ma <xma@us.ibm.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Shirley Ma 2010-01-18 19:15:23 +05:30 committed by Rusty Russell
parent 69740c8ba8
commit c021eac414
2 changed files with 29 additions and 0 deletions
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25
drivers/virtio/virtio_ring.c
View File

@ -351,6 +351,30 @@ 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);
@ -377,6 +401,7 @@ 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,

4
include/linux/virtio.h
View File

@ -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);
};
/**