On Wed, Nov 20, 2013 at 07:08:50AM -0500, Jason Wang wrote:
>
>
> ----- 原始邮件 -----
> > On Wed, Nov 20, 2013 at 05:07:26PM +0800, Jason Wang wrote:
> > > We need decrease the rq->num after we can get a buf through
> > > virtqueue_get_buf() even if we could not allocate frag skb. Otherwise, the
> > > refill routine won't be triggered under heavy memory stress since the
> > > driver may
> > > still think there's enough room.
> > >
> > > This bug was introduced by commit 2613af0ed18a11d5c566a81f9a6510b73180660a
> > > (virtio_net: migrate mergeable rx buffers to page frag allocators).
> > >
> > > Cc: Rusty Russell <ru...@rustcorp.com.au>
> > > Cc: Michael S. Tsirkin <m...@redhat.com>
> > > Cc: Michael Dalton <mwdal...@google.com>
> > > Cc: Eric Dumazet <eduma...@google.com>
> > > Signed-off-by: Jason Wang <jasow...@redhat.com>
> >
> > So let's wrap virtqueue_get_buf to make sure we get it right?
> >
>
> Ok. good idea.
So I did this (below) but the compiler is not smart enough to
avoid two branches on data path.
So I'm not sure anymore: with my patch it's pretty clear how
the code works.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
but I don't think we need to apply this.
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 11d9cc9..1cc2e43 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -296,6 +296,14 @@ static struct sk_buff *page_to_skb(struct receive_queue
*rq,
return skb;
}
+static void *rq_get_buf(struct receive_queue *rq, unsigned int *len)
+{
+ void *buf = virtqueue_get_buf(rq->vq, len);
+ if (buf)
+ rq->num--;
+ return buf;
+}
+
static struct sk_buff *receive_mergeable(struct net_device *dev,
struct receive_queue *rq,
void *buf,
@@ -315,7 +323,7 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
while (--num_buf) {
int num_skb_frags;
- buf = virtqueue_get_buf(rq->vq, &len);
+ buf = rq_get_buf(rq, &len);
if (unlikely(!buf)) {
pr_debug("%s: rx error: %d buffers out of %d missing\n",
dev->name, num_buf, hdr->mhdr.num_buffers);
@@ -329,7 +337,6 @@ static struct sk_buff *receive_mergeable(struct net_device
*dev,
}
page = virt_to_head_page(buf);
- --rq->num;
num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {
@@ -370,7 +377,7 @@ err_buf:
dev->stats.rx_dropped++;
dev_kfree_skb(head_skb);
while (--num_buf) {
- buf = virtqueue_get_buf(rq->vq, &len);
+ buf = rq_get_buf(rq, &len);
if (unlikely(!buf)) {
pr_debug("%s: rx error: %d buffers missing\n",
dev->name, num_buf);
@@ -379,7 +386,6 @@ err_buf:
}
page = virt_to_head_page(buf);
put_page(page);
- --rq->num;
}
return NULL;
}
@@ -675,9 +681,8 @@ static int virtnet_poll(struct napi_struct *napi, int
budget)
again:
while (received < budget &&
- (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
+ (buf = rq_get_buf(rq, &len)) != NULL) {
receive_buf(rq, buf, len);
- --rq->num;
received++;
}
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
