From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, Jason Wang <jasowang@redhat.com>,
eperezma@redhat.com
Subject: [PATCH RFC v5 04/13] vhost: cleanup fetch_buf return code handling
Date: Sun, 7 Jun 2020 10:11:30 -0400 [thread overview]
Message-ID: <20200607141057.704085-5-mst@redhat.com> (raw)
In-Reply-To: <20200607141057.704085-1-mst@redhat.com>
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(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 3b0609801381..5075505cfe55 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -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 */
--
MST
next prev parent reply other threads:[~2020-06-07 14:13 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-07 14:11 [PATCH RFC v5 00/13] vhost: ring format independence Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 01/13] vhost: option to fetch descriptors through an independent struct Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 02/13] vhost: use batched version by default Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 03/13] vhost: batching fetches Michael S. Tsirkin
2020-06-07 14:11 ` Michael S. Tsirkin [this message]
2020-06-07 14:11 ` [PATCH RFC v5 05/13] vhost/net: pass net specific struct pointer Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 06/13] vhost: reorder functions Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 07/13] vhost: format-independent API for used buffers Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 08/13] vhost/net: convert to new API: heads->bufs Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 09/13] vhost/net: avoid iov length math Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 10/13] vhost/test: convert to the buf API Michael S. Tsirkin
2020-06-07 14:11 ` [PATCH RFC v5 11/13] vhost/scsi: switch to buf APIs Michael S. Tsirkin
2020-06-08 9:57 ` Stefan Hajnoczi
2020-06-07 14:11 ` [PATCH RFC v5 12/13] vhost/vsock: switch to the buf API Michael S. Tsirkin
2020-06-08 9:57 ` Stefan Hajnoczi
2020-06-08 10:17 ` Stefano Garzarella
2020-06-08 13:30 ` Michael S. Tsirkin
2020-06-08 16:26 ` Stefano Garzarella
2020-06-07 14:11 ` [PATCH RFC v5 13/13] vhost: drop head based APIs Michael S. Tsirkin
2020-06-08 3:57 ` Jason Wang
2020-06-08 6:45 ` Michael S. Tsirkin
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