netdev - [RFC PATCH net-next v1 3/3] netdev: add netdev_rx_queue

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Message-ID: <20240430010732.666512-4-dw@davidwei.uk>
Date: Mon, 29 Apr 2024 18:07:32 -0700
From: David Wei <dw@...idwei.uk>
To: netdev@...r.kernel.org,
	Michael Chan <michael.chan@...adcom.com>,
	Pavan Chebbi <pavan.chebbi@...adcom.com>,
	Andy Gospodarek <andrew.gospodarek@...adcom.com>,
	Mina Almasry <almasrymina@...gle.com>,
	Shailend Chand <shailend@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>
Subject: [RFC PATCH net-next v1 3/3] netdev: add netdev_rx_queue_restart()

From: Mina Almasry <almasrymina@...gle.com>

Add netdev_rx_queue_restart() function to netdev_rx_queue.h. This is
taken from Mina's work in [1] with a slight modification of taking
rtnl_lock() during the queue stop and start ops.

For bnxt specifically, if the firmware doesn't support
BNXT_RST_RING_SP_EVENT, then ndo_queue_stop() returns -EOPNOTSUPP and
the whole restart fails. Unlike bnxt_rx_ring_reset(), there is no
attempt to reset the whole device.

[1]: https://lore.kernel.org/linux-kernel/20240403002053.2376017-6-almasrymina@google.com/#t

Signed-off-by: David Wei <dw@...idwei.uk>
---
 include/net/netdev_rx_queue.h |  3 ++
 net/core/Makefile             |  1 +
 net/core/netdev_rx_queue.c    | 58 +++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)
 create mode 100644 net/core/netdev_rx_queue.c

diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index aa1716fb0e53..e78ca52d67fb 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -54,4 +54,7 @@ get_netdev_rx_queue_index(struct netdev_rx_queue *queue)
 	return index;
 }
 #endif
+
+int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq);
+
 #endif
diff --git a/net/core/Makefile b/net/core/Makefile
index 21d6fbc7e884..f2aa63c167a3 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_NETDEV_ADDR_LIST_TEST) += dev_addr_lists_test.o
 
 obj-y += net-sysfs.o
 obj-y += hotdata.o
+obj-y += netdev_rx_queue.o
 obj-$(CONFIG_PAGE_POOL) += page_pool.o page_pool_user.o
 obj-$(CONFIG_PROC_FS) += net-procfs.o
 obj-$(CONFIG_NET_PKTGEN) += pktgen.o
diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
new file mode 100644
index 000000000000..9633fb36f6d1
--- /dev/null
+++ b/net/core/netdev_rx_queue.c
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/netdevice.h>
+#include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
+
+int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq)
+{
+	void *new_mem;
+	void *old_mem;
+	int err;
+
+	if (!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)
+		return -EOPNOTSUPP;
+
+	new_mem = dev->queue_mgmt_ops->ndo_queue_mem_alloc(dev, rxq);
+	if (!new_mem)
+		return -ENOMEM;
+
+	rtnl_lock();
+	err = dev->queue_mgmt_ops->ndo_queue_stop(dev, rxq, &old_mem);
+	if (err)
+		goto err_free_new_mem;
+
+	err = dev->queue_mgmt_ops->ndo_queue_start(dev, rxq, new_mem);
+	if (err)
+		goto err_start_queue;
+	rtnl_unlock();
+
+	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
+
+	return 0;
+
+err_start_queue:
+	/* Restarting the queue with old_mem should be successful as we haven't
+	 * changed any of the queue configuration, and there is not much we can
+	 * do to recover from a failure here.
+	 *
+	 * WARN if the 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, rxq, old_mem)) {
+		WARN(1,
+		     "Failed to restart old queue in error path. RX queue %d may be unhealthy.",
+		     rxq);
+		dev->queue_mgmt_ops->ndo_queue_mem_free(dev, &old_mem);
+	}
+
+err_free_new_mem:
+	dev->queue_mgmt_ops->ndo_queue_mem_free(dev, new_mem);
+	rtnl_unlock();
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(netdev_rx_queue_restart);
-- 
2.43.0