[PATCH RFC] net: core: support managed resource allocation in ndo_open

[Heiner Kallweit]

Quite often certain resources (irq, bigger chunks of memory) are
allocated not at probe time but in ndo_open. This requires to relaese
such resources in the right order in ndo_stop(), and in ndo_open()
error paths. Having said that the requirements are basically the same
as for releasing probe-time allocated resources in remove callback
and probe error paths.
So why not use the same mechanism to faciliate this? We have a big
number of device-managed resource allocation functions, so all we
need is a device suited for managed ndo_open resource allocation.
This RFC patch adds such a device to struct net_device. All we need
is a dozen lines of code. Resources then can be allocated with e.g.

struct device *devm = &dev->devres_up;
devm_kzalloc(devm, size, gfp);

Signed-off-by: Heiner Kallweit <hkallwe...@gmail.com>
---
 include/linux/netdevice.h |  2 ++
 net/core/dev.c            | 15 +++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 72643c193..1fd2c1f3d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1803,6 +1803,7 @@ enum netdev_priv_flags {
  *     @garp_port:     GARP
  *     @mrp_port:      MRP
  *
+ *     @devres_up:     for managed resource allocation in ndo_open()
  *     @dev:           Class/net/name entry
  *     @sysfs_groups:  Space for optional device, statistics and wireless
  *                     sysfs groups
@@ -2121,6 +2122,7 @@ struct net_device {
        struct mrp_port __rcu   *mrp_port;
 #endif
 
+       struct device           devres_up;
        struct device           dev;
        const struct attribute_group *sysfs_groups[4];
        const struct attribute_group *sysfs_rx_queue_group;
diff --git a/net/core/dev.c b/net/core/dev.c
index 81abc4f98..f2c345579 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1488,6 +1488,11 @@ void netdev_notify_peers(struct net_device *dev)
 }
 EXPORT_SYMBOL(netdev_notify_peers);
 
+static void netdev_release_devres_up(struct device *dev)
+{
+       memset(dev, 0, sizeof(*dev));
+}
+
 static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
 {
        const struct net_device_ops *ops = dev->netdev_ops;
@@ -1519,14 +1524,18 @@ static int __dev_open(struct net_device *dev, struct 
netlink_ext_ack *extack)
        if (ops->ndo_validate_addr)
                ret = ops->ndo_validate_addr(dev);
 
+       device_initialize(&dev->devres_up);
+       dev->devres_up.release = netdev_release_devres_up;
+
        if (!ret && ops->ndo_open)
                ret = ops->ndo_open(dev);
 
        netpoll_poll_enable(dev);
 
-       if (ret)
+       if (ret) {
+               put_device(&dev->devres_up);
                clear_bit(__LINK_STATE_START, &dev->state);
-       else {
+       } else {
                dev->flags |= IFF_UP;
                dev_set_rx_mode(dev);
                dev_activate(dev);
@@ -1606,6 +1615,8 @@ static void __dev_close_many(struct list_head *head)
                if (ops->ndo_stop)
                        ops->ndo_stop(dev);
 
+               put_device(&dev->devres_up);
+
                dev->flags &= ~IFF_UP;
                netpoll_poll_enable(dev);
        }
-- 
2.29.2