This helper returns 1 if a call to add_buf will not fail
with -ENOSPC.
This will help callers that do
while(1) {
alloc()
if (add_buf()) {
free();
break;
}
}
This will result in one less alloc/free exercise.
Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
---
v2:
return true/false instead of 1/0
drivers/virtio/virtio_ring.c | 8 ++++++++
include/linux/virtio.h | 5 +++++
2 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a882f26..ea7efe6 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -137,6 +137,13 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
return head;
}
+static bool vring_can_add_buf(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ return vq->num_free ? true : false;
+}
+
static int vring_add_buf(struct virtqueue *_vq,
struct scatterlist sg[],
unsigned int out,
@@ -350,6 +357,7 @@ EXPORT_SYMBOL_GPL(vring_interrupt);
static struct virtqueue_ops vring_vq_ops = {
.add_buf = vring_add_buf,
.get_buf = vring_get_buf,
+ .can_add_buf = vring_can_add_buf,
.kick = vring_kick,
.disable_cb = vring_disable_cb,
.enable_cb = vring_enable_cb,
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 4fca4f5..cc0e3aa 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -35,6 +35,9 @@ struct virtqueue {
* in_num: the number of sg which are writable (after readable ones)
* data: the token identifying the buffer.
* Returns 0 or an error.
+ * @can_add_buf: indicates whether we have a free slot to add a buffer
+ * vq: the struct virtqueue we're talking about.
+ * Returns 0 or 1.
* @kick: update after add_buf
* vq: the struct virtqueue
* After one or more add_buf calls, invoke this to kick the other side.
@@ -65,6 +68,8 @@ struct virtqueue_ops {
unsigned int in_num,
void *data);
+ bool (*can_add_buf)(struct virtqueue *vq);
+
void (*kick)(struct virtqueue *vq);
void *(*get_buf)(struct virtqueue *vq, unsigned int *len);
--
1.6.2.5
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