netdev - [PATCH v2 12/19] xen/netfront: use xenbus_setup_ring() and xenbus_teardown

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Date:   Thu, 28 Apr 2022 10:27:36 +0200
From:   Juergen Gross <jgross@...e.com>
To:     xen-devel@...ts.xenproject.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH v2 12/19] xen/netfront: use xenbus_setup_ring() and xenbus_teardown_ring()

Simplify netfront's ring creation and removal via xenbus_setup_ring()
and xenbus_teardown_ring().

Signed-off-by: Juergen Gross <jgross@...e.com>
---
 drivers/net/xen-netfront.c | 53 +++++++++-----------------------------
 1 file changed, 12 insertions(+), 41 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 966bee2a6902..65ab907aca5a 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1921,8 +1921,7 @@ static int setup_netfront(struct xenbus_device *dev,
 			struct netfront_queue *queue, unsigned int feature_split_evtchn)
 {
 	struct xen_netif_tx_sring *txs;
-	struct xen_netif_rx_sring *rxs = NULL;
-	grant_ref_t gref;
+	struct xen_netif_rx_sring *rxs;
 	int err;
 
 	queue->tx_ring_ref = INVALID_GRANT_REF;
@@ -1930,33 +1929,19 @@ static int setup_netfront(struct xenbus_device *dev,
 	queue->rx.sring = NULL;
 	queue->tx.sring = NULL;
 
-	txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
-	if (!txs) {
-		err = -ENOMEM;
-		xenbus_dev_fatal(dev, err, "allocating tx ring page");
+	err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH, (void **)&txs,
+				1, &queue->tx_ring_ref);
+	if (err)
 		goto fail;
-	}
-	SHARED_RING_INIT(txs);
-	FRONT_RING_INIT(&queue->tx, txs, XEN_PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, txs, 1, &gref);
-	if (err < 0)
-		goto fail;
-	queue->tx_ring_ref = gref;
+	XEN_FRONT_RING_INIT(&queue->tx, txs, XEN_PAGE_SIZE);
 
-	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
-	if (!rxs) {
-		err = -ENOMEM;
-		xenbus_dev_fatal(dev, err, "allocating rx ring page");
+	err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH, (void **)&rxs,
+				1, &queue->rx_ring_ref);
+	if (err)
 		goto fail;
-	}
-	SHARED_RING_INIT(rxs);
-	FRONT_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, rxs, 1, &gref);
-	if (err < 0)
-		goto fail;
-	queue->rx_ring_ref = gref;
+	XEN_FRONT_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE);
 
 	if (feature_split_evtchn)
 		err = setup_netfront_split(queue);
@@ -1972,24 +1957,10 @@ static int setup_netfront(struct xenbus_device *dev,
 
 	return 0;
 
-	/* If we fail to setup netfront, it is safe to just revoke access to
-	 * granted pages because backend is not accessing it at this point.
-	 */
  fail:
-	if (queue->rx_ring_ref != INVALID_GRANT_REF) {
-		gnttab_end_foreign_access(queue->rx_ring_ref,
-					  (unsigned long)rxs);
-		queue->rx_ring_ref = INVALID_GRANT_REF;
-	} else {
-		free_page((unsigned long)rxs);
-	}
-	if (queue->tx_ring_ref != INVALID_GRANT_REF) {
-		gnttab_end_foreign_access(queue->tx_ring_ref,
-					  (unsigned long)txs);
-		queue->tx_ring_ref = INVALID_GRANT_REF;
-	} else {
-		free_page((unsigned long)txs);
-	}
+	xenbus_teardown_ring((void **)&queue->rx.sring, 1, &queue->rx_ring_ref);
+	xenbus_teardown_ring((void **)&queue->tx.sring, 1, &queue->tx_ring_ref);
+
 	return err;
 }
 
-- 
2.34.1