[PATCH] fix multi-buffer logging with mergeable buffers

[PATCH] fix multi-buffer logging with mergeable buffers

[David L Stevens]

This patch fixes the multibuffer case of logging with
mergeable buffers.

Signed-off-by: David L Stevens <dlstevens@us.ibm.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 85519b4..d526b68 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -236,8 +236,9 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 	int seg = 0;
 	int headcount = 0;
 	unsigned d;
-	int r;
+	int r, nlogs;
 
+	nlogs = 0;
 	while (datalen > 0) {
 		if (unlikely(headcount >= VHOST_NET_MAX_SG)) {
 			r = -ENOBUFS;
@@ -245,7 +246,8 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 		}
 		d = vhost_get_desc(vq->dev, vq, vq->iov + seg,
 				   ARRAY_SIZE(vq->iov) - seg, &out,
-				   &in, log, log_num);
+				   &in, log+nlogs, log_num);
+		nlogs += log ? *log_num : 0;
 		if (d == vq->num) {
 			r = 0;
 			goto err;
@@ -263,6 +265,8 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 		seg += in;
 	}
 	*iovcount = seg;
+	if (unlikely(log))
+		*log_num = nlogs;
 	return headcount;
 err:
 	vhost_discard_desc(vq, headcount);

Re: [PATCH] fix multi-buffer logging with mergeable buffers

[Michael S. Tsirkin]

On Fri, May 07, 2010 at 01:11:08PM -0700, David L Stevens wrote:
> This patch fixes the multibuffer case of logging with
> mergeable buffers.
> 
> Signed-off-by: David L Stevens <dlstevens@us.ibm.com>

So, I folded this into your original patch submission,
this way we don't get broken logging followed
by a fix (better for bisect). Further, I think it's better to only use log_num
on success. After fixing whitespace (+ needs space around it:
didn't checkpatch complain?) I merged the below,
and rebased my tweaks patch on top.

The result can be found here:
git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git vhost-mrg-rxbuf

Compiles fine but I'm a bit busy with other things,
and didn't test at all yet, I'd appreciate testing and reports.

--

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 8ef5e3f..1964ab0 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -877,7 +877,7 @@ int vhost_get_desc_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
 	unsigned int out, in;
 	int seg = 0;
 	int headcount = 0;
-	int r;
+	int r, nlogs = 0;
 
 	while (datalen > 0) {
 		if (headcount >= VHOST_NET_MAX_SG) {
@@ -897,12 +897,18 @@ int vhost_get_desc_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
 			r = -EINVAL;
 			goto err;
 		}
+		if (unlikely(log)) {
+			nlogs += *log_num;
+			log += *log_num;
+		}
 		heads[headcount].len = iov_length(vq->iov + seg, in);
 		datalen -= heads[headcount].len;
 		++headcount;
 		seg += in;
 	}
 	*iovcount = seg;
+	if (unlikely(log))
+		*log_num = nlogs;
 	return headcount;
 err:
 	vhost_discard_desc(vq, headcount);
-- 
MST

Re: [PATCH] fix multi-buffer logging with mergeable buffers

[David Stevens]

"Michael S. Tsirkin" <mst@redhat.com> wrote on 05/09/2010 04:10:16 AM:

> On Fri, May 07, 2010 at 01:11:08PM -0700, David L Stevens wrote:
> > This patch fixes the multibuffer case of logging with
> > mergeable buffers.
> > 
> > Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
> 
> So, I folded this into your original patch submission,
> this way we don't get broken logging followed
> by a fix (better for bisect). Further, I think it's better to only use 
log_num
> on success. After fixing whitespace (+ needs space around it:
> didn't checkpatch complain?) I merged the below,
> and rebased my tweaks patch on top.
> 
> The result can be found here:
> git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git 
vhost-mrg-rxbuf
> 
> Compiles fine but I'm a bit busy with other things,
> and didn't test at all yet, I'd appreciate testing and reports.

        Looks good, and works. Thanks!

                                        +-DLS