It is impossible to use init_dummy_netdev together with alloc_netdev()
as the 'setup' argument.
This is because alloc_netdev() initializes some fields in the net_device
structure, and later init_dummy_netdev() memzero them all. This causes
some problems as reported here:
https://lore.kernel.org/all/[email protected]/
Split the init_dummy_netdev() function in two. Create a new function called
init_dummy_netdev_core() that does not memzero the net_device structure.
Then have init_dummy_netdev() memzero-ing and calling
init_dummy_netdev_core(), keeping the old behaviour.
init_dummy_netdev_core() is the new function that could be called as an
argument for alloc_netdev().
Also, create a helper to allocate and initialize dummy net devices,
leveraging init_dummy_netdev_core() as the setup argument. This function
basically simplify the allocation of dummy devices, by allocating and
initializing it. Freeing the device continue to be done through
free_netdev()
Suggested-by: Jakub Kicinski <[email protected]>
Signed-off-by: Breno Leitao <[email protected]>
Reviewed-by: Ido Schimmel <[email protected]>
---
include/linux/netdevice.h | 3 +++
net/core/dev.c | 54 ++++++++++++++++++++++++++-------------
2 files changed, 39 insertions(+), 18 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d45f330d083d..f849e7d110ed 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4519,6 +4519,9 @@ static inline void netif_addr_unlock_bh(struct net_device *dev)
void ether_setup(struct net_device *dev);
+/* Allocate dummy net_device */
+struct net_device *alloc_netdev_dummy(int sizeof_priv);
+
/* Support for loadable net-drivers */
struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
unsigned char name_assign_type,
diff --git a/net/core/dev.c b/net/core/dev.c
index c74b42bc6888..417abfd12871 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10414,25 +10414,12 @@ int register_netdevice(struct net_device *dev)
}
EXPORT_SYMBOL(register_netdevice);
-/**
- * init_dummy_netdev - init a dummy network device for NAPI
- * @dev: device to init
- *
- * This takes a network device structure and initializes the minimum
- * amount of fields so it can be used to schedule NAPI polls without
- * registering a full blown interface. This is to be used by drivers
- * that need to tie several hardware interfaces to a single NAPI
- * poll scheduler due to HW limitations.
+/* Initialize the core of a dummy net device.
+ * This is useful if you are calling this function after alloc_netdev(),
+ * since it does not memset the net_device fields.
*/
-void init_dummy_netdev(struct net_device *dev)
+static void init_dummy_netdev_core(struct net_device *dev)
{
- /* Clear everything. Note we don't initialize spinlocks
- * as they aren't supposed to be taken by any of the
- * NAPI code and this dummy netdev is supposed to be
- * only ever used for NAPI polls
- */
- memset(dev, 0, sizeof(struct net_device));
-
/* make sure we BUG if trying to hit standard
* register/unregister code path
*/
@@ -10453,8 +10440,28 @@ void init_dummy_netdev(struct net_device *dev)
* its refcount.
*/
}
-EXPORT_SYMBOL_GPL(init_dummy_netdev);
+/**
+ * init_dummy_netdev - init a dummy network device for NAPI
+ * @dev: device to init
+ *
+ * This takes a network device structure and initializes the minimum
+ * amount of fields so it can be used to schedule NAPI polls without
+ * registering a full blown interface. This is to be used by drivers
+ * that need to tie several hardware interfaces to a single NAPI
+ * poll scheduler due to HW limitations.
+ */
+void init_dummy_netdev(struct net_device *dev)
+{
+ /* Clear everything. Note we don't initialize spinlocks
+ * as they aren't supposed to be taken by any of the
+ * NAPI code and this dummy netdev is supposed to be
+ * only ever used for NAPI polls
+ */
+ memset(dev, 0, sizeof(struct net_device));
+ init_dummy_netdev_core(dev);
+}
+EXPORT_SYMBOL_GPL(init_dummy_netdev);
/**
* register_netdev - register a network device
@@ -11074,6 +11081,17 @@ void free_netdev(struct net_device *dev)
}
EXPORT_SYMBOL(free_netdev);
+/**
+ * alloc_netdev_dummy - Allocate and initialize a dummy net device.
+ * @sizeof_priv: size of private data to allocate space for
+ */
+struct net_device *alloc_netdev_dummy(int sizeof_priv)
+{
+ return alloc_netdev(sizeof_priv, "dummy#", NET_NAME_UNKNOWN,
+ init_dummy_netdev_core);
+}
+EXPORT_SYMBOL_GPL(alloc_netdev_dummy);
+
/**
* synchronize_net - Synchronize with packet receive processing
*
--
2.43.0
On Wed, 2024-04-17 at 12:51 +0200, Alexander Lobakin wrote:
> Just FYI: kdoc accepts only this pattern:
>
> * @last_param: blah
> *
> * Return: blah
>
> NOT
>
> * Returns: blah
Actually, it does accept that, the regex is "returns?". It's just
documented only as "Return" . IMHO it sometimes reads nicer as "Returns"
depending on how you phrase it, but ...
johannes
On 4/17/24 4:19 AM, Alexander Lobakin wrote:
> From: Johannes Berg <[email protected]>
> Date: Wed, 17 Apr 2024 13:11:38 +0200
>
>> On Wed, 2024-04-17 at 12:51 +0200, Alexander Lobakin wrote:
>>> Just FYI: kdoc accepts only this pattern:
>>>
>>> * @last_param: blah
>>> *
>>> * Return: blah
>>>
>>> NOT
>>>
>>> * Returns: blah
>>
>> Actually, it does accept that, the regex is "returns?". It's just
ack (Return: is documented)
> Hmm, I was sure I had warnings on "Returns:"... Not sure now.
>
Yes, either way is accepted.
> documented only as "Return" . IMHO it sometimes reads nicer as "Returns"
>> depending on how you phrase it, but ...
--
#Randy
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