linux-kernel - Re: [PATCH] netdevsim: remove incorrect __net

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Date:   Wed, 4 Apr 2018 09:33:59 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netdevsim: remove incorrect __net_initdata annotations

On 4/4/18 6:12 AM, Arnd Bergmann wrote:
> The __net_initdata section cannot currently be used for structures that
> get cleaned up in an exitcall using unregister_pernet_operations:
> 
> WARNING: vmlinux.o(.text+0x868c34): Section mismatch in reference from the function nsim_devlink_exit() to the (unknown reference) .init.data:(unknown)
> The function nsim_devlink_exit() references
> the (unknown reference) __initdata (unknown).
> This is often because nsim_devlink_exit lacks a __initdata
> annotation or the annotation of (unknown) is wrong.
> WARNING: vmlinux.o(.text+0x868c64): Section mismatch in reference from the function nsim_devlink_init() to the (unknown reference) .init.data:(unknown)
> WARNING: vmlinux.o(.text+0x8692bc): Section mismatch in reference from the function nsim_fib_exit() to the (unknown reference) .init.data:(unknown)
> WARNING: vmlinux.o(.text+0x869300): Section mismatch in reference from the function nsim_fib_init() to the (unknown reference) .init.data:(unknown)
> 
> As that warning tells us, discarding the structure after a module is
> loaded would lead to a undefined behavior when that module is removed.
> 
> It might be possible to change that annotation so it has no effect for
> loadable modules, but I have not figured out exactly how to do that, and
> we want this to be fixed in -rc1.
> 
> This just removes the annotations, just like we do for all other such
> modules.
> 
> Fixes: 37923ed6b8ce ("netdevsim: Add simple FIB resource controller via devlink")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/netdevsim/devlink.c | 2 +-
>  drivers/net/netdevsim/fib.c     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/netdevsim/devlink.c b/drivers/net/netdevsim/devlink.c
> index 27ae05c5fdaf..1dba47936456 100644
> --- a/drivers/net/netdevsim/devlink.c
> +++ b/drivers/net/netdevsim/devlink.c
> @@ -267,7 +267,7 @@ static int __net_init nsim_devlink_netns_init(struct net *net)
>  	return 0;
>  }
>  
> -static struct pernet_operations nsim_devlink_net_ops __net_initdata = {
> +static struct pernet_operations nsim_devlink_net_ops = {
>  	.init = nsim_devlink_netns_init,
>  	.id   = &nsim_devlink_id,
>  	.size = sizeof(bool),
> diff --git a/drivers/net/netdevsim/fib.c b/drivers/net/netdevsim/fib.c
> index 0d105bafa261..9bfe9e151e13 100644
> --- a/drivers/net/netdevsim/fib.c
> +++ b/drivers/net/netdevsim/fib.c
> @@ -230,7 +230,7 @@ static int __net_init nsim_fib_netns_init(struct net *net)
>  	return 0;
>  }
>  
> -static struct pernet_operations nsim_fib_net_ops __net_initdata = {
> +static struct pernet_operations nsim_fib_net_ops = {
>  	.init = nsim_fib_netns_init,
>  	.id   = &nsim_fib_net_id,
>  	.size = sizeof(struct nsim_fib_data),
> 

I am confused ... I do the same thing in the VRF driver and that code
has been there since June 2017.