[RFC PATCH v1 10/16] virtio/vsock: update SEQPACKET dequeue logic

From: Arseny Krasnov
Date: Mon Jun 28 2021 - 06:04:14 EST


As message copied by fragments, in addition to EOR met,
dequeue loop iterates until queue will be empty or copy
error found.

Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
---
include/linux/virtio_vsock.h | 1 -
net/vmw_vsock/virtio_transport_common.c | 61 ++++++++++---------------
2 files changed, 25 insertions(+), 37 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 8d34f3d73bbb..7360ab7ea0af 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -36,7 +36,6 @@ struct virtio_vsock_sock {
u32 rx_bytes;
u32 buf_alloc;
struct list_head rx_queue;
- u32 msg_count;
};

struct virtio_vsock_pkt {
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 9c2bd84ab8e6..5a46c3f94e83 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -407,59 +407,48 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,

static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
struct msghdr *msg,
- int flags)
+ int flags,
+ bool *msg_ready)
{
struct virtio_vsock_sock *vvs = vsk->trans;
struct virtio_vsock_pkt *pkt;
int dequeued_len = 0;
size_t user_buf_len = msg_data_left(msg);
- bool msg_ready = false;

+ *msg_ready = false;
spin_lock_bh(&vvs->rx_lock);

- if (vvs->msg_count == 0) {
- spin_unlock_bh(&vvs->rx_lock);
- return 0;
- }
+ while (!*msg_ready && !list_empty(&vvs->rx_queue) && dequeued_len >= 0) {
+ size_t pkt_len;
+ size_t bytes_to_copy;

- while (!msg_ready) {
pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list);
+ pkt_len = (size_t)le32_to_cpu(pkt->hdr.len);

- if (dequeued_len >= 0) {
- size_t pkt_len;
- size_t bytes_to_copy;
+ bytes_to_copy = min(user_buf_len, pkt_len);

- pkt_len = (size_t)le32_to_cpu(pkt->hdr.len);
- bytes_to_copy = min(user_buf_len, pkt_len);
-
- if (bytes_to_copy) {
- int err;
-
- /* sk_lock is held by caller so no one else can dequeue.
- * Unlock rx_lock since memcpy_to_msg() may sleep.
- */
- spin_unlock_bh(&vvs->rx_lock);
+ if (bytes_to_copy) {
+ int err;
+ /* sk_lock is held by caller so no one else can dequeue.
+ * Unlock rx_lock since memcpy_to_msg() may sleep.
+ */
+ spin_unlock_bh(&vvs->rx_lock);

- err = memcpy_to_msg(msg, pkt->buf, bytes_to_copy);
- if (err) {
- /* Copy of message failed. Rest of
- * fragments will be freed without copy.
- */
- dequeued_len = err;
- } else {
- user_buf_len -= bytes_to_copy;
- }
+ err = memcpy_to_msg(msg, pkt->buf, bytes_to_copy);

- spin_lock_bh(&vvs->rx_lock);
- }
+ spin_lock_bh(&vvs->rx_lock);

- if (dequeued_len >= 0)
- dequeued_len += pkt_len;
+ if (err)
+ dequeued_len = err;
+ else
+ user_buf_len -= bytes_to_copy;
}

+ if (dequeued_len >= 0)
+ dequeued_len += pkt_len;
+
if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
- msg_ready = true;
- vvs->msg_count--;
+ *msg_ready = true;
}

virtio_transport_dec_rx_pkt(vvs, pkt);
@@ -494,7 +483,7 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
if (flags & MSG_PEEK)
return -EOPNOTSUPP;

- return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags);
+ return virtio_transport_seqpacket_do_dequeue(vsk, msg, flags, msg_ready);
}
EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);

--
2.25.1