Add netdev_rx_queue_restart() function to netdev_rx_queue.h

Signed-off-by: David Wei <d...@davidwei.uk>
Signed-off-by: Mina Almasry <almasrym...@google.com>
Reviewed-by: Pavel Begunkov <asml.sile...@gmail.com>

---

v13:
- Add reviewed-by from Pavel (thanks!)
- Fixed comment (Pavel)

v11:
- Fix not checking dev->queue_mgmt_ops (Pavel).
- Fix ndo_queue_mem_free call that passed the wrong pointer (David).

v9: https://lore.kernel.org/all/20240502045410.3524155-4...@davidwei.uk/
(submitted by David).
- fixed SPDX license identifier (Simon).
- Rebased on top of merged queue API definition, and changed
  implementation to match that.
- Replace rtnl_lock() with rtnl_is_locked() to make it useable from my
  netlink code where rtnl is already locked.

---
 include/net/netdev_rx_queue.h |  3 ++
 net/core/Makefile             |  1 +
 net/core/netdev_rx_queue.c    | 74 +++++++++++++++++++++++++++++++++++
 3 files changed, 78 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 aa1716fb0e53c..e78ca52d67fbf 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 62be9aef25285..f82232b358a2c 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 0000000000000..cf15ffecfa368
--- /dev/null
+++ b/net/core/netdev_rx_queue.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#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_idx)
+{
+       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)
+               return -EOPNOTSUPP;
+
+       DEBUG_NET_WARN_ON_ONCE(!rtnl_is_locked());
+
+       new_mem = kvzalloc(dev->queue_mgmt_ops->ndo_queue_mem_size, GFP_KERNEL);
+       if (!new_mem)
+               return -ENOMEM;
+
+       old_mem = kvzalloc(dev->queue_mgmt_ops->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);
+       if (err)
+               goto err_free_old_mem;
+
+       err = dev->queue_mgmt_ops->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;
+
+       dev->queue_mgmt_ops->ndo_queue_mem_free(dev, old_mem);
+
+       kvfree(old_mem);
+       kvfree(new_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 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)) {
+               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);
+       }
+
+err_free_new_queue_mem:
+       dev->queue_mgmt_ops->ndo_queue_mem_free(dev, new_mem);
+
+err_free_old_mem:
+       kvfree(old_mem);
+
+err_free_new_mem:
+       kvfree(new_mem);
+
+       return err;
+}
-- 
2.45.2.741.gdbec12cfda-goog

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