From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: "Eugenio Pérez" <eperezma@redhat.com>,
"Jason Wang" <jasowang@redhat.com>,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org
Subject: [PATCH RFC 04/13] vhost: cleanup fetch_buf return code handling
Date: Tue, 2 Jun 2020 09:06:03 -0400 [thread overview]
Message-ID: <20200602130543.578420-5-mst@redhat.com> (raw)
In-Reply-To: <20200602130543.578420-1-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 aca2a5b0d078..bd52b44b0d23 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2146,6 +2146,8 @@ 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;
@@ -2162,7 +2164,7 @@ 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",
@@ -2181,7 +2183,7 @@ 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.
@@ -2251,12 +2253,14 @@ 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;
@@ -2266,10 +2270,14 @@ 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
@@ -2288,7 +2296,7 @@ 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:[~2020-06-02 13:07 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-02 13:05 [PATCH RFC 00/13] vhost: format independence Michael S. Tsirkin
2020-06-02 13:05 ` [PATCH RFC 01/13] vhost: option to fetch descriptors through an independent struct Michael S. Tsirkin
2020-06-03 7:13 ` Jason Wang
2020-06-03 9:48 ` Michael S. Tsirkin
2020-06-03 12:04 ` Jason Wang
2020-06-07 13:59 ` Michael S. Tsirkin
2020-06-02 13:05 ` [PATCH RFC 02/13] vhost: use batched version by default Michael S. Tsirkin
2020-06-03 7:15 ` Jason Wang
2020-06-02 13:06 ` [PATCH RFC 03/13] vhost: batching fetches Michael S. Tsirkin
2020-06-03 7:27 ` Jason Wang
2020-06-04 8:59 ` Michael S. Tsirkin
2020-06-05 3:40 ` Jason Wang
2020-06-07 13:57 ` Michael S. Tsirkin
2020-06-08 3:35 ` Jason Wang
2020-06-08 6:01 ` Michael S. Tsirkin
2020-06-02 13:06 ` Michael S. Tsirkin [this message]
2020-06-03 7:29 ` [PATCH RFC 04/13] vhost: cleanup fetch_buf return code handling Jason Wang
2020-06-04 9:01 ` Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 05/13] vhost/net: pass net specific struct pointer Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 06/13] vhost: reorder functions Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 07/13] vhost: format-independent API for used buffers Michael S. Tsirkin
2020-06-03 7:58 ` Jason Wang
2020-06-04 9:03 ` Michael S. Tsirkin
2020-06-04 9:18 ` Jason Wang
2020-06-04 10:17 ` Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 08/13] vhost/net: convert to new API: heads->bufs Michael S. Tsirkin
2020-06-03 8:11 ` Jason Wang
2020-06-04 9:05 ` Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 09/13] vhost/net: avoid iov length math Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 10/13] vhost/test: convert to the buf API Michael S. Tsirkin
2020-06-02 13:06 ` [PATCH RFC 11/13] vhost/scsi: switch to buf APIs Michael S. Tsirkin
2020-06-05 8:36 ` Stefan Hajnoczi
2020-06-02 13:06 ` [PATCH RFC 12/13] vhost/vsock: switch to the buf API Michael S. Tsirkin
2020-06-05 8:36 ` Stefan Hajnoczi
2020-06-02 13:06 ` [PATCH RFC 13/13] vhost: drop head based APIs Michael S. Tsirkin
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