Pavel Emelyanov wrote:
> To make some per-net generic pointers, we need some way to
> address them, i.e. - IDs. This is simple IDA-based IDs
> generator for pernet subsystems. They will be used in the
> next patches.
> 
> Since it will be used by devices only (tun and vlan), I make
> it resemble the register_pernet_device functionality.
> 
> The new ids is stored in the *id pointer _before_ calling the
> init callback to make this id available in this callback.
> 
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
> 
> ---
>  include/net/net_namespace.h |    2 ++
>  net/core/net_namespace.c    |   36 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+), 0 deletions(-)
> 
> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index 0ab62ed..6971fdb 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -181,6 +181,8 @@ extern int register_pernet_subsys(struct pernet_operations *);
>  extern void unregister_pernet_subsys(struct pernet_operations *);
>  extern int register_pernet_device(struct pernet_operations *);
>  extern void unregister_pernet_device(struct pernet_operations *);
> +extern int register_pernet_gen_device(int *id, struct pernet_operations *);
> +extern void unregister_pernet_gen_device(int id, struct pernet_operations *);
> 
>  struct ctl_path;
>  struct ctl_table;
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 7b66083..7ef3bac 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -5,6 +5,7 @@
>  #include <linux/list.h>
>  #include <linux/delay.h>
>  #include <linux/sched.h>
> +#include <linux/idr.h>
>  #include <net/net_namespace.h>
> 
>  /*
> @@ -253,6 +254,8 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
>  }
>  #endif
> 
> +static DEFINE_IDA(net_generic_ids);
> +
>  /**
>   *      register_pernet_subsys - register a network namespace subsystem
>   *	@ops:  pernet operations structure for the subsystem
> @@ -330,6 +333,28 @@ int register_pernet_device(struct pernet_operations *ops)
>  }
>  EXPORT_SYMBOL_GPL(register_pernet_device);
> 
> +int register_pernet_gen_device(int *id, struct pernet_operations *ops)
> +{
> +	int error;
> +	mutex_lock(&net_mutex);
> +again:
> +	error = ida_get_new_above(&net_generic_ids, 1, id);
> +	if (error) {
> +		if (error == -EAGAIN) {
> +			ida_pre_get(&net_generic_ids, GFP_KERNEL);
> +			goto again;
> +		}

		goto out;

> +	}
> +	error = register_pernet_operations(first_device, ops);
> +	if (error)
> +		ida_remove(&net_generic_ids, *id);
> +	else if (first_device == &pernet_list)
> +		first_device = &ops->list;

out:

> +	mutex_unlock(&net_mutex);
> +	return error;
> +}
> +EXPORT_SYMBOL_GPL(register_pernet_gen_device);
> +
>  /**
>   *      unregister_pernet_device - unregister a network namespace netdevice
>   *	@ops: pernet operations structure to manipulate
> @@ -348,3 +373,14 @@ void unregister_pernet_device(struct pernet_operations *ops)
>  	mutex_unlock(&net_mutex);
>  }
>  EXPORT_SYMBOL_GPL(unregister_pernet_device);
> +
> +void unregister_pernet_gen_device(int id, struct pernet_operations *ops)
> +{
> +	mutex_lock(&net_mutex);
> +	if (&ops->list == first_device)
> +		first_device = first_device->next;
> +	unregister_pernet_operations(ops);
> +	ida_remove(&net_generic_ids, id);
> +	mutex_unlock(&net_mutex);
> +}
> +EXPORT_SYMBOL_GPL(unregister_pernet_gen_device);


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