| Message ID | 4a3f3978-1093-4c0a-663f-28d77eeb0806@sberdevices.ru (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | virtio/vsock: fix credit update logic | expand |
On Sun, Mar 05, 2023 at 11:06:26PM +0300, Arseniy Krasnov wrote: >Substraction of 'skb->len' is redundant here: 'skb_headroom()' is delta >between 'data' and 'head' pointers, e.g. it is number of bytes returned >to user (of course accounting size of header). 'skb->len' is number of >bytes rest in buffer. > >Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") >Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >--- > net/vmw_vsock/virtio_transport_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >index a1581c77cf84..2e2a773df5c1 100644 >--- a/net/vmw_vsock/virtio_transport_common.c >+++ b/net/vmw_vsock/virtio_transport_common.c >@@ -255,7 +255,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs, > { > int len; > >- len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr) - skb->len; >+ len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr); IIUC virtio_transport_dec_rx_pkt() is always called after skb_pull(), so skb_headroom() is returning the amount of space we removed. Looking at the other patches in this series, I think maybe we should change virtio_transport_dec_rx_pkt() and virtio_transport_inc_rx_pkt() by passing the value to subtract or add directly. Since some times we don't remove the whole payload, so it would be better to call it with the value in hdr->len. I mean something like this (untested): index a1581c77cf84..9e69ae7a9a96 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -241,21 +241,18 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, } static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, - struct sk_buff *skb) + u32 len) { - if (vvs->rx_bytes + skb->len > vvs->buf_alloc) + if (vvs->rx_bytes + len > vvs->buf_alloc) return false; - vvs->rx_bytes += skb->len; + vvs->rx_bytes += len; return true; } static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs, - struct sk_buff *skb) + u32 len) { - int len; - - len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr) - skb->len; vvs->rx_bytes -= len; vvs->fwd_cnt += len; } @@ -388,7 +385,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, skb_pull(skb, bytes); if (skb->len == 0) { - virtio_transport_dec_rx_pkt(vvs, skb); + virtio_transport_dec_rx_pkt(vvs, bytes); consume_skb(skb); } else { __skb_queue_head(&vvs->rx_queue, skb); @@ -437,17 +434,17 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk, while (!msg_ready) { struct virtio_vsock_hdr *hdr; + size_t pkt_len; skb = __skb_dequeue(&vvs->rx_queue); if (!skb) break; hdr = virtio_vsock_hdr(skb); + pkt_len = (size_t)le32_to_cpu(hdr->len); if (dequeued_len >= 0) { - size_t pkt_len; size_t bytes_to_copy; - pkt_len = (size_t)le32_to_cpu(hdr->len); bytes_to_copy = min(user_buf_len, pkt_len); if (bytes_to_copy) { @@ -484,7 +481,7 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk, msg->msg_flags |= MSG_EOR; } - virtio_transport_dec_rx_pkt(vvs, skb); + virtio_transport_dec_rx_pkt(vvs, pkt_len); kfree_skb(skb); } @@ -1040,7 +1037,7 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk, spin_lock_bh(&vvs->rx_lock); - can_enqueue = virtio_transport_inc_rx_pkt(vvs, skb); + can_enqueue = virtio_transport_inc_rx_pkt(vvs, len); if (!can_enqueue) { free_pkt = true; goto out; When we used vsock_pkt, we were passing the structure because the `len` field was immutable (and copied from the header), whereas with skb it can change and so we introduced these errors. What do you think? Thanks, Stefano
On 06.03.2023 14:57, Stefano Garzarella wrote: > On Sun, Mar 05, 2023 at 11:06:26PM +0300, Arseniy Krasnov wrote: >> Substraction of 'skb->len' is redundant here: 'skb_headroom()' is delta >> between 'data' and 'head' pointers, e.g. it is number of bytes returned >> to user (of course accounting size of header). 'skb->len' is number of >> bytes rest in buffer. >> >> Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") >> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >> --- >> net/vmw_vsock/virtio_transport_common.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >> index a1581c77cf84..2e2a773df5c1 100644 >> --- a/net/vmw_vsock/virtio_transport_common.c >> +++ b/net/vmw_vsock/virtio_transport_common.c >> @@ -255,7 +255,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs, >> { >> int len; >> >> - len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr) - skb->len; >> + len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr); > > IIUC virtio_transport_dec_rx_pkt() is always called after skb_pull(), > so skb_headroom() is returning the amount of space we removed. > > Looking at the other patches in this series, I think maybe we should > change virtio_transport_dec_rx_pkt() and virtio_transport_inc_rx_pkt() > by passing the value to subtract or add directly. > Since some times we don't remove the whole payload, so it would be > better to call it with the value in hdr->len. > > I mean something like this (untested): > > index a1581c77cf84..9e69ae7a9a96 100644 > --- a/net/vmw_vsock/virtio_transport_common.c > +++ b/net/vmw_vsock/virtio_transport_common.c > @@ -241,21 +241,18 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > } > > static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, > - struct sk_buff *skb) > + u32 len) > { > - if (vvs->rx_bytes + skb->len > vvs->buf_alloc) > + if (vvs->rx_bytes + len > vvs->buf_alloc) > return false; > > - vvs->rx_bytes += skb->len; > + vvs->rx_bytes += len; > return true; > } > > static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs, > - struct sk_buff *skb) > + u32 len) > { > - int len; > - > - len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr) - skb->len; > vvs->rx_bytes -= len; > vvs->fwd_cnt += len; > } > @@ -388,7 +385,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, > skb_pull(skb, bytes); > > if (skb->len == 0) { > - virtio_transport_dec_rx_pkt(vvs, skb); > + virtio_transport_dec_rx_pkt(vvs, bytes); > consume_skb(skb); > } else { > __skb_queue_head(&vvs->rx_queue, skb); > @@ -437,17 +434,17 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk, > > while (!msg_ready) { > struct virtio_vsock_hdr *hdr; > + size_t pkt_len; > > skb = __skb_dequeue(&vvs->rx_queue); > if (!skb) > break; > hdr = virtio_vsock_hdr(skb); > + pkt_len = (size_t)le32_to_cpu(hdr->len); > > if (dequeued_len >= 0) { > - size_t pkt_len; > size_t bytes_to_copy; > > - pkt_len = (size_t)le32_to_cpu(hdr->len); > bytes_to_copy = min(user_buf_len, pkt_len); > > if (bytes_to_copy) { > @@ -484,7 +481,7 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk, > msg->msg_flags |= MSG_EOR; > } > > - virtio_transport_dec_rx_pkt(vvs, skb); > + virtio_transport_dec_rx_pkt(vvs, pkt_len); > kfree_skb(skb); > } > > @@ -1040,7 +1037,7 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk, > > spin_lock_bh(&vvs->rx_lock); > > - can_enqueue = virtio_transport_inc_rx_pkt(vvs, skb); > + can_enqueue = virtio_transport_inc_rx_pkt(vvs, len); > if (!can_enqueue) { > free_pkt = true; > goto out; > > When we used vsock_pkt, we were passing the structure because the `len` > field was immutable (and copied from the header), whereas with skb it > can change and so we introduced these errors. > > What do you think? Yes, i think passing explicit integer value to 'virtio_transport_inc/dec_rx_pkt' is more clear solution. I had this variant, but thought that current will be smaller. Current version with skb argument forces to call 'skb_pull()' before each 'virtio_transport_dec_rx_pkt()' as 'rx_bytes'/'fwd_cnt' new value relies on skb parameters - otherwise 'rx_bytes' become invalid. 'skb_pull()' will be used only to update 'skb->len' which shows rest of the data. I'll do it in v3. Thanks, Arseniy > > Thanks, > Stefano >
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index a1581c77cf84..2e2a773df5c1 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -255,7 +255,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs, { int len; - len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr) - skb->len; + len = skb_headroom(skb) - sizeof(struct virtio_vsock_hdr); vvs->rx_bytes -= len; vvs->fwd_cnt += len; }
Substraction of 'skb->len' is redundant here: 'skb_headroom()' is delta between 'data' and 'head' pointers, e.g. it is number of bytes returned to user (of course accounting size of header). 'skb->len' is number of bytes rest in buffer. Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> --- net/vmw_vsock/virtio_transport_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)