Subject: Re: [PATCH 3/4] SUNRPC: service destruction in network namespace context

From: "J. Bruce Fields" <[email-masked]>
Date: Thu, 26 Jan 2012 16:14:50 -0500

On Wed, Jan 25, 2012 at 05:47:26PM +0400, Stanislav Kinsbursky wrote:
> This patch introduces network namespace filter for service destruction
> function.
> Nothing special here - just do exactly the same operations, but only for
> tranports in passed networks namespace context.
> BTW, BUG_ON() checks for empty service transports lists were returned into
> svc_destroy() function. This is because of swithing generic svc_close_all() to
> networks namespace dependable svc_close_net().
> 
> Signed-off-by: Stanislav Kinsbursky <[email-masked]>
> 
> ---
>  include/linux/sunrpc/svcsock.h |    2 +-
>  net/sunrpc/svc.c               |    9 +++++++--
>  net/sunrpc/svc_xprt.c          |   27 +++++++++++++++++----------
>  3 files changed, 25 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index c84e974..cb4ac69 100644
> --- a/include/linux/sunrpc/svcsock.h
> +++ b/include/linux/sunrpc/svcsock.h
> @@ -34,7 +34,7 @@ struct svc_sock {
>  /*
>   * Function prototypes.
>   */
> -void		svc_close_all(struct svc_serv *);
> +void		svc_close_net(struct svc_serv *, struct net *);
>  int		svc_recv(struct svc_rqst *, long);
>  int		svc_send(struct svc_rqst *);
>  void		svc_drop(struct svc_rqst *);
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index a8b49a0..279bbd8 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -517,6 +517,8 @@ EXPORT_SYMBOL_GPL(svc_create_pooled);
>  void
>  svc_destroy(struct svc_serv *serv)
>  {
> +	struct net *net = current->nsproxy->net_ns;
> +
>  	dprintk("svc: svc_destroy(%s, %d)\n",
>  				serv->sv_program->pg_name,
>  				serv->sv_nrthreads);
> @@ -539,10 +541,13 @@ svc_destroy(struct svc_serv *serv)
>  	 * caller is using--nfsd_mutex in the case of nfsd).  So it's
>  	 * safe to traverse those lists and shut everything down:
>  	 */
> -	svc_close_all(serv);
> +	svc_close_net(serv, net);
> +
> +	BUG_ON(!list_empty(&serv->sv_permsocks));
> +	BUG_ON(!list_empty(&serv->sv_tempsocks));

I'm confused--what guarantees this is true, at this point?

There are two ways I could imagine containerizing svc_serv: either we
create a new one for each namespace, or we share a single global one
between them.

If the former, then something that takes a "serv" argument shouldn't
also need a "net" argument--the serv should already know which namespace
it belongs to.

If the latter, then these lists could have sockets from multiple
namespaces, and they aren't guaranteed to be empty here.

?

--b.

>  
>  	if (serv->sv_shutdown)
> -		serv->sv_shutdown(serv, current->nsproxy->net_ns);
> +		serv->sv_shutdown(serv, net);
>  
>  	cache_clean_deferred(serv);
>  
> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
> index 493e70b..4bda09d 100644
> --- a/net/sunrpc/svc_xprt.c
> +++ b/net/sunrpc/svc_xprt.c
> @@ -922,17 +922,19 @@ void svc_close_xprt(struct svc_xprt *xprt)
>  }
>  EXPORT_SYMBOL_GPL(svc_close_xprt);
>  
> -static void svc_close_list(struct list_head *xprt_list)
> +static void svc_close_list(struct list_head *xprt_list, struct net *net)
>  {
>  	struct svc_xprt *xprt;
>  
>  	list_for_each_entry(xprt, xprt_list, xpt_list) {
> +		if (xprt->xpt_net != net)
> +			continue;
>  		set_bit(XPT_CLOSE, &xprt->xpt_flags);
>  		set_bit(XPT_BUSY, &xprt->xpt_flags);
>  	}
>  }
>  
> -static void svc_clear_pools(struct svc_serv *serv)
> +static void svc_clear_pools(struct svc_serv *serv, struct net *net)
>  {
>  	struct svc_pool *pool;
>  	struct svc_xprt *xprt;
> @@ -944,36 +946,41 @@ static void svc_clear_pools(struct svc_serv *serv)
>  
>  		spin_lock_bh(&pool->sp_lock);
>  		list_for_each_entry_safe(xprt, tmp, &pool->sp_sockets, xpt_ready) {
> +			if (xprt->xpt_net != net)
> +				continue;
>  			list_del_init(&xprt->xpt_ready);
>  		}
>  		spin_unlock_bh(&pool->sp_lock);
>  	}
>  }
>  
> -static void svc_clear_list(struct list_head *xprt_list)
> +static void svc_clear_list(struct list_head *xprt_list, struct net *net)
>  {
>  	struct svc_xprt *xprt;
>  	struct svc_xprt *tmp;
>  
>  	list_for_each_entry_safe(xprt, tmp, xprt_list, xpt_list) {
> +		if (xprt->xpt_net != net)
> +			continue;
>  		svc_delete_xprt(xprt);
>  	}
> -	BUG_ON(!list_empty(xprt_list));
> +	list_for_each_entry(xprt, xprt_list, xpt_list)
> +		BUG_ON(xprt->xpt_net == net);
>  }
>  
> -void svc_close_all(struct svc_serv *serv)
> +void svc_close_net(struct svc_serv *serv, struct net *net)
>  {
> -	svc_close_list(&serv->sv_tempsocks);
> -	svc_close_list(&serv->sv_permsocks);
> +	svc_close_list(&serv->sv_tempsocks, net);
> +	svc_close_list(&serv->sv_permsocks, net);
>  
> -	svc_clear_pools(serv);
> +	svc_clear_pools(serv, net);
>  	/*
>  	 * At this point the sp_sockets lists will stay empty, since
>  	 * svc_enqueue will not add new entries without taking the
>  	 * sp_lock and checking XPT_BUSY.
>  	 */
> -	svc_clear_list(&serv->sv_tempsocks);
> -	svc_clear_list(&serv->sv_permsocks);
> +	svc_clear_list(&serv->sv_tempsocks, net);
> +	svc_clear_list(&serv->sv_permsocks, net);
>  }
>  
>  /*
> 
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