@@ -2189,6 +2189,8 @@ static int fetch_indirect_descs(struct vhost_virtqueue *vq,
return 0;
}
+/* This function returns a value > 0 if a descriptor was found, or 0 if none were found.
+ * A negative code is returned on error. */
static int fetch_buf(struct vhost_virtqueue *vq)
{
unsigned int i, head, found = 0;
@@ -2205,7 +2207,7 @@ static int fetch_buf(struct vhost_virtqueue *vq)
if (unlikely(vq->avail_idx == vq->last_avail_idx)) {
/* If we already have work to do, don't bother re-checking. */
if (likely(vq->ndescs))
- return vq->num;
+ return 0;
if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) {
vq_err(vq, "Failed to access avail idx at %p\n",
@@ -2224,7 +2226,7 @@ static int fetch_buf(struct vhost_virtqueue *vq)
* invalid.
*/
if (vq->avail_idx == last_avail_idx)
- return vq->num;
+ return 0;
/* Only get avail ring entries after they have been
* exposed by guest.
@@ -2294,12 +2296,14 @@ static int fetch_buf(struct vhost_virtqueue *vq)
/* On success, increment avail index. */
vq->last_avail_idx++;
- return 0;
+ return 1;
}
+/* This function returns a value > 0 if a descriptor was found, or 0 if none were found.
+ * A negative code is returned on error. */
static int fetch_descs(struct vhost_virtqueue *vq)
{
- int ret = 0;
+ int ret;
if (unlikely(vq->first_desc >= vq->ndescs)) {
vq->first_desc = 0;
@@ -2309,10 +2313,14 @@ static int fetch_descs(struct vhost_virtqueue *vq)
if (vq->ndescs)
return 0;
- while (!ret && vq->ndescs <= vhost_vq_num_batch_descs(vq))
- ret = fetch_buf(vq);
+ for (ret = 1;
+ ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq);
+ ret = fetch_buf(vq))
+ ;
- return vq->ndescs ? 0 : ret;
+ /* On success we expect some descs */
+ BUG_ON(ret > 0 && !vq->ndescs);
+ return ret;
}
/* This looks in the virtqueue and for the first available buffer, and converts
@@ -2331,7 +2339,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
int ret = fetch_descs(vq);
int i;
- if (ret)
+ if (ret <= 0)
return ret;
/* Now convert to IOV */
Return code of fetch_buf is confusing, so callers resort to tricks to get to sane values. Let's switch to something standard: 0 empty, >0 non-empty, <0 error. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- drivers/vhost/vhost.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-)