| Message ID | 20210601064000.66909-3-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 8fb7da9e990793299c89ed7a4281c235bfdd31f8 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio-net: fix for build_skb() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 5 maintainers not CCed: yhs@fb.com kpsingh@kernel.org andrii@kernel.org kafai@fb.com songliubraving@fb.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 24 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
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;
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;
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(-)