[Xen-devel] [PATCH net-next v2] xen-netfront: always set num queues if possible

["Charles (Chas) Williams" <3chas3@xxxxxxxxx>]

If netfront connects with two (or more) queues and then reconnects with
only one queue it fails to delete or rewrite the multi-queue-num-queues
key and netback will try to use the wrong number of queues.

Always write the num-queues field if the backend has multi-queue support.

Signed-off-by: Chas Williams <3chas3@xxxxxxxxx>
---
 drivers/net/xen-netfront.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index f821a97..9bf63c2 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1819,19 +1819,22 @@ again:
                goto destroy_ring;
        }
 
-       if (num_queues == 1) {
-               err = write_queue_xenstore_keys(&info->queues[0], &xbt, 0); /* 
flat */
-               if (err)
-                       goto abort_transaction_no_dev_fatal;
-       } else {
+       if (xenbus_exists(XBT_NIL,
+                         info->xbdev->otherend, "multi-queue-max-queues")) {
                /* Write the number of queues */
-               err = xenbus_printf(xbt, dev->nodename, 
"multi-queue-num-queues",
-                                   "%u", num_queues);
+               err = xenbus_printf(xbt, dev->nodename,
+                                   "multi-queue-num-queues", "%u", num_queues);
                if (err) {
                        message = "writing multi-queue-num-queues";
                        goto abort_transaction_no_dev_fatal;
                }
+       }
 
+       if (num_queues == 1) {
+               err = write_queue_xenstore_keys(&info->queues[0], &xbt, 0); /* 
flat */
+               if (err)
+                       goto abort_transaction_no_dev_fatal;
+       } else {
                /* Write the keys for each queue */
                for (i = 0; i < num_queues; ++i) {
                        queue = &info->queues[i];
-- 
2.1.0




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