Merge branch 'net-improve-core-queue-api-handling-while-device-is-down'

Jakub Kicinski says:

====================
net: improve core queue API handling while device is down

The core netdev_rx_queue_restart() doesn't currently take into account
that the device may be down. The current and proposed queue API
implementations deal with this by rejecting queue API calls while
the device is down. We can do better, in theory we can still allow
devmem binding when the device is down - we shouldn't stop and start
the queues just try to allocate the memory. The reason we allocate
the memory is that memory provider binding checks if any compatible
page pool has been created (page_pool_check_memory_provider()).

Alternatively we could reject installing MP while the device is down
but the MP assignment survives ifdown (so presumably MP doesn't cease
to exist while down), and in general we allow configuration while down.

Previously I thought we need this as a fix, but gve rejects page pool
calls while down, and so did Saeed in the patches he posted. So this
series just makes the core act more sensibly but practically should
be a noop for now.

v1: https://lore.kernel.org/20250205190131.564456-1-kuba@kernel.org
====================

Link: https://patch.msgid.link/20250206225638.1387810-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 20 insertions, 17 deletions

diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index db46880f37cc..ddd54e1e7289 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -10,28 +10,27 @@
 int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 {
 	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);
+	const struct netdev_queue_mgmt_ops *qops = dev->queue_mgmt_ops;
 	void *new_mem, *old_mem;
 	int err;
 
-	if (!dev->queue_mgmt_ops || !dev->queue_mgmt_ops->ndo_queue_stop ||
-	    !dev->queue_mgmt_ops->ndo_queue_mem_free ||
-	    !dev->queue_mgmt_ops->ndo_queue_mem_alloc ||
-	    !dev->queue_mgmt_ops->ndo_queue_start)
+	if (!qops || !qops->ndo_queue_stop || !qops->ndo_queue_mem_free ||
+	    !qops->ndo_queue_mem_alloc || !qops->ndo_queue_start)
 		return -EOPNOTSUPP;
 
 	ASSERT_RTNL();
 
-	new_mem = kvzalloc(dev->queue_mgmt_ops->ndo_queue_mem_size, GFP_KERNEL);
+	new_mem = kvzalloc(qops->ndo_queue_mem_size, GFP_KERNEL);
 	if (!new_mem)
 		return -ENOMEM;
 
-	old_mem = kvzalloc(dev->queue_mgmt_ops->ndo_queue_mem_size, GFP_KERNEL);
+	old_mem = kvzalloc(qops->ndo_queue_mem_size, GFP_KERNEL);
 	if (!old_mem) {
 		err = -ENOMEM;
 		goto err_free_new_mem;
 	}
 
-	err = dev->queue_mgmt_ops->ndo_queue_mem_alloc(dev, new_mem, rxq_idx);
+	err = qops->ndo_queue_mem_alloc(dev, new_mem, rxq_idx);
 	if (err)
 		goto err_free_old_mem;
 
@@ -39,15 +38,19 @@ int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 	if (err)
 		goto err_free_new_queue_mem;
 
-	err = dev->queue_mgmt_ops->ndo_queue_stop(dev, old_mem, rxq_idx);
-	if (err)
-		goto err_free_new_queue_mem;
+	if (netif_running(dev)) {
+		err = qops->ndo_queue_stop(dev, old_mem, rxq_idx);
+		if (err)
+			goto err_free_new_queue_mem;
 
-	err = dev->queue_mgmt_ops->ndo_queue_start(dev, new_mem, rxq_idx);
-	if (err)
-		goto err_start_queue;
+		err = qops->ndo_queue_start(dev, new_mem, rxq_idx);
+		if (err)
+			goto err_start_queue;
+	} else {
+		swap(new_mem, old_mem);
+	}
 
-	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
+	qops->ndo_queue_mem_free(dev, old_mem);
 
 	kvfree(old_mem);
 	kvfree(new_mem);
@@ -62,15 +65,15 @@ err_start_queue:
 	 * WARN if we fail to recover the old rx queue, and at least free
 	 * old_mem so we don't also leak that.
 	 */
-	if (dev->queue_mgmt_ops->ndo_queue_start(dev, old_mem, rxq_idx)) {
+	if (qops->ndo_queue_start(dev, old_mem, rxq_idx)) {
 		WARN(1,
 		     "Failed to restart old queue in error path. RX queue %d may be unhealthy.",
 		     rxq_idx);
-		dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
+		qops->ndo_queue_mem_free(dev, old_mem);
 	}
 
 err_free_new_queue_mem:
-	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, new_mem);
+	qops->ndo_queue_mem_free(dev, new_mem);
 
 err_free_old_mem:
 	kvfree(old_mem);