From: Jason Wang <jasowang@redhat.com> To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>, netdev@vger.kernel.org Cc: "Michael S. Tsirkin" <mst@redhat.com>, "David S. Miller" <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, Jesper Dangaard Brouer <hawk@kernel.org>, John Fastabend <john.fastabend@gmail.com>, virtualization@lists.linux-foundation.org, bpf@vger.kernel.org Subject: Re: [PATCH net v2 2/2] virtio_net: get build_skb() buf by data ptr Date: Tue, 1 Jun 2021 16:55:46 +0800 [thread overview] Message-ID: <3e0f4152-b41f-5cd4-ee38-95bae89ad1b2@redhat.com> (raw) In-Reply-To: <20210601064000.66909-3-xuanzhuo@linux.alibaba.com> 在 2021/6/1 下午2:40, Xuan Zhuo 写道: > In the case of merge, the page passed into page_to_skb() may be a head > page, not the page where the current data is located. So when trying to > get the buf where the data is located, we should get buf based on > headroom instead of offset. > > This patch solves this problem. But if you don't use this patch, the > original code can also run, because if the page is not the page of the > current data, the calculated tailroom will be less than 0, and will not > enter the logic of build_skb() . The significance of this patch is to > modify this logical problem, allowing more situations to use > build_skb(). > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > drivers/net/virtio_net.c | 17 ++++++----------- > 1 file changed, 6 insertions(+), 11 deletions(-) Acked-by: Jason Wang <jasowang@redhat.com> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 6b929aca155a..fa407eb8b457 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -401,18 +401,13 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, > /* If headroom is not 0, there is an offset between the beginning of the > * data and the allocated space, otherwise the data and the allocated > * space are aligned. > + * > + * Buffers with headroom use PAGE_SIZE as alloc size, see > + * add_recvbuf_mergeable() + get_mergeable_buf_len() > */ > - if (headroom) { > - /* Buffers with headroom use PAGE_SIZE as alloc size, > - * see add_recvbuf_mergeable() + get_mergeable_buf_len() > - */ > - truesize = PAGE_SIZE; > - tailroom = truesize - len - offset; > - buf = page_address(page); > - } else { > - tailroom = truesize - len; > - buf = p; > - } > + truesize = headroom ? PAGE_SIZE : truesize; > + tailroom = truesize - len - headroom; > + buf = p - headroom; > > len -= hdr_len; > offset += hdr_padded_len;
WARNING: multiple messages have this Message-ID (diff)
From: Jason Wang <jasowang@redhat.com> To: Xuan Zhuo <xuanzhuo@linux.alibaba.com>, netdev@vger.kernel.org Cc: Jesper Dangaard Brouer <hawk@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, "Michael S. Tsirkin" <mst@redhat.com>, John Fastabend <john.fastabend@gmail.com>, Alexei Starovoitov <ast@kernel.org>, virtualization@lists.linux-foundation.org, Jakub Kicinski <kuba@kernel.org>, bpf@vger.kernel.org, "David S. Miller" <davem@davemloft.net> Subject: Re: [PATCH net v2 2/2] virtio_net: get build_skb() buf by data ptr Date: Tue, 1 Jun 2021 16:55:46 +0800 [thread overview] Message-ID: <3e0f4152-b41f-5cd4-ee38-95bae89ad1b2@redhat.com> (raw) In-Reply-To: <20210601064000.66909-3-xuanzhuo@linux.alibaba.com> 在 2021/6/1 下午2:40, Xuan Zhuo 写道: > In the case of merge, the page passed into page_to_skb() may be a head > page, not the page where the current data is located. So when trying to > get the buf where the data is located, we should get buf based on > headroom instead of offset. > > This patch solves this problem. But if you don't use this patch, the > original code can also run, because if the page is not the page of the > current data, the calculated tailroom will be less than 0, and will not > enter the logic of build_skb() . The significance of this patch is to > modify this logical problem, allowing more situations to use > build_skb(). > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > drivers/net/virtio_net.c | 17 ++++++----------- > 1 file changed, 6 insertions(+), 11 deletions(-) Acked-by: Jason Wang <jasowang@redhat.com> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 6b929aca155a..fa407eb8b457 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -401,18 +401,13 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, > /* If headroom is not 0, there is an offset between the beginning of the > * data and the allocated space, otherwise the data and the allocated > * space are aligned. > + * > + * Buffers with headroom use PAGE_SIZE as alloc size, see > + * add_recvbuf_mergeable() + get_mergeable_buf_len() > */ > - if (headroom) { > - /* Buffers with headroom use PAGE_SIZE as alloc size, > - * see add_recvbuf_mergeable() + get_mergeable_buf_len() > - */ > - truesize = PAGE_SIZE; > - tailroom = truesize - len - offset; > - buf = page_address(page); > - } else { > - tailroom = truesize - len; > - buf = p; > - } > + truesize = headroom ? PAGE_SIZE : truesize; > + tailroom = truesize - len - headroom; > + buf = p - headroom; > > len -= hdr_len; > offset += hdr_padded_len; _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-06-01 8:55 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-01 6:39 [PATCH net v2 0/2] virtio-net: fix for build_skb() Xuan Zhuo 2021-06-01 6:39 ` Xuan Zhuo 2021-06-01 6:39 ` [PATCH net v2 1/2] virtio-net: fix for unable to handle page fault for address Xuan Zhuo 2021-06-01 6:39 ` Xuan Zhuo 2021-06-01 8:53 ` Jason Wang 2021-06-01 8:53 ` Jason Wang 2021-06-01 6:40 ` [PATCH net v2 2/2] virtio_net: get build_skb() buf by data ptr Xuan Zhuo 2021-06-01 6:40 ` Xuan Zhuo 2021-06-01 8:55 ` Jason Wang [this message] 2021-06-01 8:55 ` Jason Wang 2021-06-01 11:06 ` [PATCH net v2 0/2] virtio-net: fix for build_skb() Michael S. Tsirkin 2021-06-01 11:06 ` Michael S. Tsirkin 2021-07-30 12:16 ` Jakub Kicinski 2021-08-02 4:45 ` Jason Wang 2021-08-02 4:45 ` Jason Wang 2021-08-02 16:58 ` Michael S. Tsirkin 2021-08-02 16:58 ` Michael S. Tsirkin 2021-06-01 22:30 ` patchwork-bot+netdevbpf
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