linux-kernel - [PATCH 16/18] xen/pvcalls: implement read

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Message-Id: <1494880570-14209-16-git-send-email-sstabellini@kernel.org>
Date:   Mon, 15 May 2017 13:36:08 -0700
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     xen-devel@...ts.xen.org
Cc:     linux-kernel@...r.kernel.org, sstabellini@...nel.org,
        jgross@...e.com, boris.ostrovsky@...cle.com,
        Stefano Stabellini <stefano@...reto.com>
Subject: [PATCH 16/18] xen/pvcalls: implement read

When an active socket has data available, add the relative sock_mapping
to the ioworker list, increment the io and read counters, and schedule
the ioworker.

Implement the read function by reading from the socket, writing the data
to the data ring.

Set in_error on error.

Signed-off-by: Stefano Stabellini <stefano@...reto.com>
CC: boris.ostrovsky@...cle.com
CC: jgross@...e.com
---
 drivers/xen/pvcalls-back.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index db3e02c..0f715a8 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -102,6 +102,79 @@ static int pvcalls_back_release_active(struct xenbus_device *dev,
 
 static void pvcalls_conn_back_read(unsigned long opaque)
 {
+	struct sock_mapping *map = (struct sock_mapping *)opaque;
+	struct msghdr msg;
+	struct kvec vec[2];
+	RING_IDX cons, prod, size, wanted, array_size, masked_prod, masked_cons;
+	int32_t error;
+	struct pvcalls_data_intf *intf = map->ring;
+	struct pvcalls_data *data = &map->data;
+	int ret;
+
+	array_size = XEN_FLEX_RING_SIZE(map->ring_order);
+	cons = intf->in_cons;
+	prod = intf->in_prod;
+	error = intf->in_error;
+	/* read the indexes first, then deal with the data */
+	virt_mb();
+
+	if (error)
+		return;
+
+	size = pvcalls_queued(prod, cons, array_size);
+	if (size >= array_size)
+		return;
+	lock_sock(map->sock->sk);
+	if (skb_queue_empty(&map->sock->sk->sk_receive_queue)) {
+		atomic_set(&map->read, 0);
+		release_sock(map->sock->sk);
+		return;
+	}
+	release_sock(map->sock->sk);
+	wanted = array_size - size;
+	masked_prod = pvcalls_mask(prod, array_size);
+	masked_cons = pvcalls_mask(cons, array_size);
+
+	memset(&msg, 0, sizeof(msg));
+	msg.msg_iter.type = ITER_KVEC|WRITE;
+	msg.msg_iter.count = wanted;
+	if (masked_prod < masked_cons) {
+		vec[0].iov_base = data->in + masked_prod;
+		vec[0].iov_len = wanted;
+		msg.msg_iter.kvec = vec;
+		msg.msg_iter.nr_segs = 1;
+	} else {
+		vec[0].iov_base = data->in + masked_prod;
+		vec[0].iov_len = array_size - masked_prod;
+		vec[1].iov_base = data->in;
+		vec[1].iov_len = wanted - vec[0].iov_len;
+		msg.msg_iter.kvec = vec;
+		msg.msg_iter.nr_segs = 2;
+	}
+
+	atomic_set(&map->read, 0);
+	ret = inet_recvmsg(map->sock, &msg, wanted, MSG_DONTWAIT);
+	WARN_ON(ret > 0 && ret > wanted);
+	if (ret == -EAGAIN) /* shouldn't happen */
+		return;
+	if (!ret)
+		ret = -ENOTCONN;
+	lock_sock(map->sock->sk);
+	if (ret > 0 && !skb_queue_empty(&map->sock->sk->sk_receive_queue))
+		atomic_inc(&map->read);
+	release_sock(map->sock->sk);
+
+	/* write the data, then modify the indexes */
+	virt_wmb();
+	if (ret < 0)
+		intf->in_error = ret;
+	else
+		intf->in_prod = prod + ret;
+	/* update the indexes, then notify the other end */
+	virt_wmb();
+	notify_remote_via_irq(map->irq);
+
+	return;
 }
 
 static int pvcalls_conn_back_write(struct sock_mapping *map)
@@ -192,6 +265,22 @@ static void pvcalls_sk_state_change(struct sock *sock)
 
 static void pvcalls_sk_data_ready(struct sock *sock)
 {
+	struct sock_mapping *map = sock->sk_user_data;
+	struct pvcalls_ioworker *iow;
+	unsigned long flags;
+
+	if (map == NULL)
+		return;
+
+	iow = &pvcalls_back_global.ioworkers[map->data_worker];
+	spin_lock_irqsave(&iow->lock, flags);
+	atomic_inc(&map->read);
+	if (list_empty(&map->queue))
+		list_add_tail(&map->queue, &iow->wqs);
+	spin_unlock_irqrestore(&iow->lock, flags);
+	atomic_inc(&iow->io);
+	queue_work_on(map->data_worker, pvcalls_back_global.wq,
+		&iow->register_work);
 }
 
 static int pvcalls_back_connect(struct xenbus_device *dev,
-- 
1.9.1