[v2] allocate dummy device dynamically

[PATCH net-next v2 2/5] net: marvell: prestera: allocate dummy net_device dynamically

Posted by Breno Leitao 5 months, 3 weeks ago

Embedding net_device into structures prohibits the usage of flexible
arrays in the net_device structure. For more details, see the discussion
at [1].

Un-embed the net_device from the private struct by converting it
into a pointer. Then use the leverage the new alloc_netdev_dummy()
helper to allocate and initialize dummy devices.

[1] https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 .../net/ethernet/marvell/prestera/prestera_rxtx.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c b/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c
index cc2a9ae794be..ed33a201a0f5 100644
--- a/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c
+++ b/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c
@@ -96,7 +96,7 @@ struct prestera_sdma {
 	struct dma_pool *desc_pool;
 	struct work_struct tx_work;
 	struct napi_struct rx_napi;
-	struct net_device napi_dev;
+	struct net_device *napi_dev;
 	u32 map_addr;
 	u64 dma_mask;
 	/* protect SDMA with concurrent access from multiple CPUs */
@@ -654,13 +654,21 @@ static int prestera_sdma_switch_init(struct prestera_switch *sw)
 	if (err)
 		goto err_evt_register;
 
-	init_dummy_netdev(&sdma->napi_dev);
+	sdma->napi_dev = alloc_netdev_dummy(0);
+	if (!sdma->napi_dev) {
+		dev_err(dev, "not able to initialize dummy device\n");
+		goto err_alloc_dummy;
+	}
+
 
-	netif_napi_add(&sdma->napi_dev, &sdma->rx_napi, prestera_sdma_rx_poll);
+	netif_napi_add(sdma->napi_dev, &sdma->rx_napi, prestera_sdma_rx_poll);
 	napi_enable(&sdma->rx_napi);
 
 	return 0;
 
+err_alloc_dummy:
+	prestera_hw_event_handler_unregister(sw, PRESTERA_EVENT_TYPE_RXTX,
+					     prestera_rxtx_handle_event);
 err_evt_register:
 err_tx_init:
 	prestera_sdma_tx_fini(sdma);
@@ -682,6 +690,7 @@ static void prestera_sdma_switch_fini(struct prestera_switch *sw)
 	prestera_sdma_tx_fini(sdma);
 	prestera_sdma_rx_fini(sdma);
 	dma_pool_destroy(sdma->desc_pool);
+	kfree(sdma->napi_dev);
 }
 
 static bool prestera_sdma_is_ready(struct prestera_sdma *sdma)
-- 
2.43.0

Re: [PATCH net-next v2 2/5] net: marvell: prestera: allocate dummy net_device dynamically

Posted by Simon Horman 5 months, 3 weeks ago

On Thu, Mar 28, 2024 at 04:52:02PM -0700, Breno Leitao wrote:
> Embedding net_device into structures prohibits the usage of flexible
> arrays in the net_device structure. For more details, see the discussion
> at [1].
> 
> Un-embed the net_device from the private struct by converting it
> into a pointer. Then use the leverage the new alloc_netdev_dummy()
> helper to allocate and initialize dummy devices.
> 
> [1] https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
>  .../net/ethernet/marvell/prestera/prestera_rxtx.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c b/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c

...

> @@ -654,13 +654,21 @@ static int prestera_sdma_switch_init(struct prestera_switch *sw)
>  	if (err)
>  		goto err_evt_register;
>  
> -	init_dummy_netdev(&sdma->napi_dev);
> +	sdma->napi_dev = alloc_netdev_dummy(0);
> +	if (!sdma->napi_dev) {
> +		dev_err(dev, "not able to initialize dummy device\n");
> +		goto err_alloc_dummy;

Hi Breno,

This goto will result in the function returning err.
But err is 0 here. Perhaps it should be set to a negative error value
instead?

Flagged by Smatch.

> +	}
> +
>  
> -	netif_napi_add(&sdma->napi_dev, &sdma->rx_napi, prestera_sdma_rx_poll);
> +	netif_napi_add(sdma->napi_dev, &sdma->rx_napi, prestera_sdma_rx_poll);
>  	napi_enable(&sdma->rx_napi);
>  
>  	return 0;
>  
> +err_alloc_dummy:
> +	prestera_hw_event_handler_unregister(sw, PRESTERA_EVENT_TYPE_RXTX,
> +					     prestera_rxtx_handle_event);
>  err_evt_register:
>  err_tx_init:
>  	prestera_sdma_tx_fini(sdma);

...

Re: [PATCH net-next v2 2/5] net: marvell: prestera: allocate dummy net_device dynamically

Posted by Breno Leitao 5 months, 2 weeks ago

On Sun, Mar 31, 2024 at 09:54:38AM +0100, Simon Horman wrote:
> On Thu, Mar 28, 2024 at 04:52:02PM -0700, Breno Leitao wrote:
> > Embedding net_device into structures prohibits the usage of flexible
> > arrays in the net_device structure. For more details, see the discussion
> > at [1].
> > 
> > Un-embed the net_device from the private struct by converting it
> > into a pointer. Then use the leverage the new alloc_netdev_dummy()
> > helper to allocate and initialize dummy devices.
> > 
> > [1] https://lore.kernel.org/all/20240229225910.79e224cf@kernel.org/
> > 
> > Signed-off-by: Breno Leitao <leitao@debian.org>
> > ---
> >  .../net/ethernet/marvell/prestera/prestera_rxtx.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c b/drivers/net/ethernet/marvell/prestera/prestera_rxtx.c
> 
> ...
> 
> > @@ -654,13 +654,21 @@ static int prestera_sdma_switch_init(struct prestera_switch *sw)
> >  	if (err)
> >  		goto err_evt_register;
> >  
> > -	init_dummy_netdev(&sdma->napi_dev);
> > +	sdma->napi_dev = alloc_netdev_dummy(0);
> > +	if (!sdma->napi_dev) {
> > +		dev_err(dev, "not able to initialize dummy device\n");
> > +		goto err_alloc_dummy;
> 
> Hi Breno,
> 
> This goto will result in the function returning err.
> But err is 0 here. Perhaps it should be set to a negative error value
> instead?

Definitely, that was a good catch.

> Flagged by Smatch.

I am curious how you are running Smatch. I tried to run it here
according to[1] , and I found different and valid errors also, that I
will fix soon. For instance:

   drivers/net/ethernet/marvell/prestera/prestera_main.c:433 prestera_port_sfp_bind() error: uninitialized symbol 'err'.
   drivers/net/ethernet/marvell/prestera/prestera_main.c:861 prestera_switch_set_base_mac_addr() error: uninitialized symbol 'ret'.

[1] https://rajanvaja.wordpress.com/2021/02/06/how-to-run-smatch-on-linux-kernel/

Thanks

Re: [PATCH net-next v2 2/5] net: marvell: prestera: allocate dummy net_device dynamically

Posted by Jakub Kicinski 5 months, 3 weeks ago

On Thu, 28 Mar 2024 16:52:02 -0700 Breno Leitao wrote:
> -	init_dummy_netdev(&sdma->napi_dev);
> +	sdma->napi_dev = alloc_netdev_dummy(0);
> +	if (!sdma->napi_dev) {
> +		dev_err(dev, "not able to initialize dummy device\n");
> +		goto err_alloc_dummy;
> +	}
> +
>  

duplicated empty line here

> -	netif_napi_add(&sdma->napi_dev, &sdma->rx_napi, prestera_sdma_rx_poll);
> +	netif_napi_add(sdma->napi_dev, &sdma->rx_napi, prestera_sdma_rx_poll);
>  	napi_enable(&sdma->rx_napi);
>  
>  	return 0;
>  
> +err_alloc_dummy:
> +	prestera_hw_event_handler_unregister(sw, PRESTERA_EVENT_TYPE_RXTX,
> +					     prestera_rxtx_handle_event);
>  err_evt_register:
>  err_tx_init:
>  	prestera_sdma_tx_fini(sdma);
> @@ -682,6 +690,7 @@ static void prestera_sdma_switch_fini(struct prestera_switch *sw)
>  	prestera_sdma_tx_fini(sdma);
>  	prestera_sdma_rx_fini(sdma);
>  	dma_pool_destroy(sdma->desc_pool);
> +	kfree(sdma->napi_dev);

Why kfree()? Let's use free_netdev() consistently, in case one day
we have to undo something alloc_netdev_dummy() has done.

Re: [PATCH net-next v2 2/5] net: marvell: prestera: allocate dummy net_device dynamically

Posted by Breno Leitao 5 months, 3 weeks ago

On Fri, Mar 29, 2024 at 08:56:33AM -0700, Jakub Kicinski wrote:
> > @@ -682,6 +690,7 @@ static void prestera_sdma_switch_fini(struct prestera_switch *sw)
> >  	prestera_sdma_tx_fini(sdma);
> >  	prestera_sdma_rx_fini(sdma);
> >  	dma_pool_destroy(sdma->desc_pool);
> > +	kfree(sdma->napi_dev);
> 
> Why kfree()? Let's use free_netdev() consistently, in case one day
> we have to undo something alloc_netdev_dummy() has done.

I should have used free_netdev() in fact. I will update.