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

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Message-ID: <20210628100401.571282-1-arseny.krasnov@kaspersky.com>
Date:   Mon, 28 Jun 2021 13:03:58 +0300
From:   Arseny Krasnov <arseny.krasnov@...persky.com>
To:     Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Arseny Krasnov <arseny.krasnov@...persky.com>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>
CC:     <kvm@...r.kernel.org>, <virtualization@...ts.linux-foundation.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <oxffffaa@...il.com>
Subject: [RFC PATCH v1 10/16] virtio/vsock: update SEQPACKET dequeue logic

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@...persky.com>
---
 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