linux-kernel - [PATCH 13/18] xen/pvcalls: implement release command

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Date:   Mon, 15 May 2017 13:36:05 -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 13/18] xen/pvcalls: implement release command

Release both active and passive sockets. For active sockets, make sure
to avoid possible conflicts with the ioworker reading/writing to those
sockets concurrently. Set map->release to let the ioworker know
atomically that the socket will be released soon, then wait until the
ioworker removed the socket from its list.

Unmap indexes pages and data rings.

Signed-off-by: Stefano Stabellini <stefano@...reto.com>
CC: boris.ostrovsky@...cle.com
CC: jgross@...e.com
---
 drivers/xen/pvcalls-back.c | 94 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 93 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index d5b7412..22c6426 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -253,13 +253,105 @@ static int pvcalls_back_release_active(struct xenbus_device *dev,
 				       struct pvcalls_back_priv *priv,
 				       struct sock_mapping *map)
 {
+	struct pvcalls_ioworker *iow =
+	    &pvcalls_back_global.ioworkers[map->data_worker];
+	unsigned long flags;
+	bool in_loop = false;
+
+
+	disable_irq(map->irq);
+	if (map->sock->sk != NULL) {
+		lock_sock(map->sock->sk);
+		map->sock->sk->sk_user_data = NULL;
+		map->sock->sk->sk_data_ready = map->saved_data_ready;
+		release_sock(map->sock->sk);
+	}
+
+	atomic_set(&map->release, 1);
+
+	/*
+	 * To avoid concurrency problems with ioworker, check if the socket
+	 * has any outstanding io requests. If so, wait until the ioworker
+	 * removes it from the list before proceeding.
+	 */
+	spin_lock_irqsave(&iow->lock, flags);
+	in_loop = !list_empty(&map->queue);
+	spin_unlock_irqrestore(&iow->lock, flags);
+
+	if (in_loop) {
+		atomic_inc(&iow->io);
+		queue_work_on(map->data_worker, pvcalls_back_global.wq,
+			      &iow->register_work);
+		while (atomic_read(&map->release) > 0)
+			cond_resched();
+	}
+
+	down_write(&priv->pvcallss_lock);
+	list_del(&map->list);
+	up_write(&priv->pvcallss_lock);
+
+	xenbus_unmap_ring_vfree(dev, (void *)map->bytes);
+	xenbus_unmap_ring_vfree(dev, (void *)map->ring);
+	unbind_from_irqhandler(map->irq, map);
+
+	sock_release(map->sock);
+	kfree(map);
+
+	return 0;
+}
+
+static int pvcalls_back_release_passive(struct xenbus_device *dev,
+					struct pvcalls_back_priv *priv,
+					struct sockpass_mapping *mappass)
+{
+	if (mappass->sock->sk != NULL) {
+		lock_sock(mappass->sock->sk);
+		mappass->sock->sk->sk_user_data = NULL;
+		mappass->sock->sk->sk_data_ready = mappass->saved_data_ready;
+		release_sock(mappass->sock->sk);
+	}
+	down_write(&priv->pvcallss_lock);
+	radix_tree_delete(&priv->socketpass_mappings, mappass->id);
+	sock_release(mappass->sock);
+	flush_workqueue(mappass->wq);
+	destroy_workqueue(mappass->wq);
+	kfree(mappass);
+	up_write(&priv->pvcallss_lock);
+
 	return 0;
 }
 
 static int pvcalls_back_release(struct xenbus_device *dev,
 				struct xen_pvcalls_request *req)
 {
-	return 0;
+	struct pvcalls_back_priv *priv;
+	struct sock_mapping *map, *n;
+	struct sockpass_mapping *mappass;
+	int ret = 0;
+	struct xen_pvcalls_response *rsp;
+
+	priv = dev_get_drvdata(&dev->dev);
+
+	list_for_each_entry_safe(map, n, &priv->socket_mappings, list) {
+		if (map->id == req->u.release.id) {
+			ret = pvcalls_back_release_active(dev, priv, map);
+			goto out;
+		}
+	}
+	mappass = radix_tree_lookup(&priv->socketpass_mappings,
+				    req->u.release.id);
+	if (mappass != NULL) {
+		ret = pvcalls_back_release_passive(dev, priv, mappass);
+		goto out;
+	}
+
+out:
+	rsp = RING_GET_RESPONSE(&priv->ring, priv->ring.rsp_prod_pvt++);
+	rsp->req_id = req->req_id;
+	rsp->u.release.id = req->u.release.id;
+	rsp->cmd = req->cmd;
+	rsp->ret = ret;
+	return 1;
 }
 
 static void __pvcalls_back_accept(struct work_struct *work)
-- 
1.9.1