Re: [PATCH 05/14] SUNRPC: remove timeout arg from svc_recv()

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2023-07-18 at 16:38 +1000, NeilBrown wrote:
> Most svc threads have no interest in a timeout.
> nfsd sets it to 1 hour, but this is a wart of no significance.
> 
> lockd uses the timeout so that it can call nlmsvc_retry_blocked().
> It also sometimes calls svc_wake_up() to ensure this is called.
> 
> So change lockd to be consistent and always use svc_wake_up() to trigger
> nlmsvc_retry_blocked() - using a timer instead of a timeout to
> svc_recv().
> 
> And change svc_recv() to not take a timeout arg.
> 
> This makes the sp_threads_timedout counter always zero.
> 
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  fs/lockd/svc.c                 |   11 ++++++++---
>  fs/lockd/svclock.c             |    5 +++--
>  fs/nfs/callback.c              |    2 +-
>  fs/nfsd/nfssvc.c               |    2 +-
>  include/linux/lockd/lockd.h    |    4 +++-
>  include/linux/sunrpc/svc.h     |    1 -
>  include/linux/sunrpc/svcsock.h |    2 +-
>  net/sunrpc/svc.c               |    2 --
>  net/sunrpc/svc_xprt.c          |   27 ++++++++++++---------------
>  9 files changed, 29 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
> index a43b63e46127..4f55cd42c2e6 100644
> --- a/fs/lockd/svc.c
> +++ b/fs/lockd/svc.c
> @@ -55,6 +55,11 @@ static DEFINE_MUTEX(nlmsvc_mutex);
>  static unsigned int		nlmsvc_users;
>  static struct svc_serv		*nlmsvc_serv;
>  unsigned long			nlmsvc_timeout;
> +static void nlmsvc_request_retry(struct timer_list *tl)
> +{
> +	svc_wake_up(nlmsvc_serv);
> +}
> +DEFINE_TIMER(nlmsvc_retry, nlmsvc_request_retry);
>  
>  unsigned int lockd_net_id;
>  
> @@ -130,18 +135,17 @@ lockd(void *vrqstp)
>  	 * NFS mount or NFS daemon has gone away.
>  	 */
>  	while (!kthread_should_stop()) {
> -		long timeout = MAX_SCHEDULE_TIMEOUT;
>  
>  		/* update sv_maxconn if it has changed */
>  		rqstp->rq_server->sv_maxconn = nlm_max_connections;
>  
> -		timeout = nlmsvc_retry_blocked();
> +		nlmsvc_retry_blocked();
>  
>  		/*
>  		 * Find any work to do, such as a socket with data available,
>  		 * and do the work.
>  		 */
> -		svc_recv(rqstp, timeout);
> +		svc_recv(rqstp);
>  	}
>  	if (nlmsvc_ops)
>  		nlmsvc_invalidate_all();
> @@ -375,6 +379,7 @@ static void lockd_put(void)
>  #endif
>  
>  	svc_set_num_threads(nlmsvc_serv, NULL, 0);
> +	timer_delete_sync(&nlmsvc_retry);
>  	nlmsvc_serv = NULL;
>  	dprintk("lockd_down: service destroyed\n");
>  }
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index c43ccdf28ed9..3d7bd5c04b36 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -1008,7 +1008,7 @@ retry_deferred_block(struct nlm_block *block)
>   * picks up locks that can be granted, or grant notifications that must
>   * be retransmitted.
>   */
> -unsigned long
> +void
>  nlmsvc_retry_blocked(void)
>  {
>  	unsigned long	timeout = MAX_SCHEDULE_TIMEOUT;
> @@ -1038,5 +1038,6 @@ nlmsvc_retry_blocked(void)
>  	}
>  	spin_unlock(&nlm_blocked_lock);
>  
> -	return timeout;
> +	if (timeout < MAX_SCHEDULE_TIMEOUT)
> +		mod_timer(&nlmsvc_retry, jiffies + timeout);
>  }
> diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
> index 914d2402ca98..c47834970224 100644
> --- a/fs/nfs/callback.c
> +++ b/fs/nfs/callback.c
> @@ -82,7 +82,7 @@ nfs4_callback_svc(void *vrqstp)
>  		/*
>  		 * Listen for a request on the socket
>  		 */
> -		svc_recv(rqstp, MAX_SCHEDULE_TIMEOUT);
> +		svc_recv(rqstp);
>  	}
>  
>  	svc_exit_thread(rqstp);
> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> index 5bf48c33986e..b536b254c59e 100644
> --- a/fs/nfsd/nfssvc.c
> +++ b/fs/nfsd/nfssvc.c
> @@ -979,7 +979,7 @@ nfsd(void *vrqstp)
>  		 * Find a socket with data available and call its
>  		 * recvfrom routine.
>  		 */
> -		svc_recv(rqstp, 60*60*HZ);
> +		svc_recv(rqstp);
>  		validate_process_creds();
>  	}
>  
> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
> index f42594a9efe0..0f016d69c996 100644
> --- a/include/linux/lockd/lockd.h
> +++ b/include/linux/lockd/lockd.h
> @@ -204,6 +204,8 @@ extern unsigned long		nlmsvc_timeout;
>  extern bool			nsm_use_hostnames;
>  extern u32			nsm_local_state;
>  
> +extern struct timer_list	nlmsvc_retry;
> +
>  /*
>   * Lockd client functions
>   */
> @@ -280,7 +282,7 @@ __be32		  nlmsvc_testlock(struct svc_rqst *, struct nlm_file *,
>  			struct nlm_host *, struct nlm_lock *,
>  			struct nlm_lock *, struct nlm_cookie *);
>  __be32		  nlmsvc_cancel_blocked(struct net *net, struct nlm_file *, struct nlm_lock *);
> -unsigned long	  nlmsvc_retry_blocked(void);
> +void		  nlmsvc_retry_blocked(void);
>  void		  nlmsvc_traverse_blocks(struct nlm_host *, struct nlm_file *,
>  					nlm_host_match_fn_t match);
>  void		  nlmsvc_grant_reply(struct nlm_cookie *, __be32);
> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> index d51ae1e109b6..f3df7f963653 100644
> --- a/include/linux/sunrpc/svc.h
> +++ b/include/linux/sunrpc/svc.h
> @@ -41,7 +41,6 @@ struct svc_pool {
>  	struct percpu_counter	sp_messages_arrived;
>  	struct percpu_counter	sp_sockets_queued;
>  	struct percpu_counter	sp_threads_woken;
> -	struct percpu_counter	sp_threads_timedout;
>  	struct percpu_counter	sp_threads_starved;
>  	struct percpu_counter	sp_threads_no_work;
>  
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index fb5c98069356..8da31799affe 100644
> --- a/include/linux/sunrpc/svcsock.h
> +++ b/include/linux/sunrpc/svcsock.h
> @@ -64,7 +64,7 @@ static inline u32 svc_sock_final_rec(struct svc_sock *svsk)
>   * Function prototypes.
>   */
>  void		svc_close_net(struct svc_serv *, struct net *);
> -void		svc_recv(struct svc_rqst *, long);
> +void		svc_recv(struct svc_rqst *);
>  void		svc_send(struct svc_rqst *rqstp);
>  void		svc_drop(struct svc_rqst *);
>  void		svc_sock_update_bufs(struct svc_serv *serv);
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index f09b0cce041c..170eabc03988 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -513,7 +513,6 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
>  		percpu_counter_init(&pool->sp_messages_arrived, 0, GFP_KERNEL);
>  		percpu_counter_init(&pool->sp_sockets_queued, 0, GFP_KERNEL);
>  		percpu_counter_init(&pool->sp_threads_woken, 0, GFP_KERNEL);
> -		percpu_counter_init(&pool->sp_threads_timedout, 0, GFP_KERNEL);
>  		percpu_counter_init(&pool->sp_threads_starved, 0, GFP_KERNEL);
>  		percpu_counter_init(&pool->sp_threads_no_work, 0, GFP_KERNEL);
>  
> @@ -593,7 +592,6 @@ svc_destroy(struct kref *ref)
>  		percpu_counter_destroy(&pool->sp_messages_arrived);
>  		percpu_counter_destroy(&pool->sp_sockets_queued);
>  		percpu_counter_destroy(&pool->sp_threads_woken);
> -		percpu_counter_destroy(&pool->sp_threads_timedout);
>  		percpu_counter_destroy(&pool->sp_threads_starved);
>  		percpu_counter_destroy(&pool->sp_threads_no_work);
>  	}
> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
> index 67825eef8646..44a33b1f542f 100644
> --- a/net/sunrpc/svc_xprt.c
> +++ b/net/sunrpc/svc_xprt.c
> @@ -735,10 +735,9 @@ rqst_should_sleep(struct svc_rqst *rqstp)
>  	return true;
>  }
>  
> -static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
> +static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp)
>  {
>  	struct svc_pool		*pool = rqstp->rq_pool;
> -	long			time_left = 0;
>  
>  	/* rq_xprt should be clear on entry */
>  	WARN_ON_ONCE(rqstp->rq_xprt);
> @@ -756,7 +755,7 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
>  	smp_mb__after_atomic();
>  
>  	if (likely(rqst_should_sleep(rqstp)))
> -		time_left = schedule_timeout(timeout);
> +		schedule();
>  	else
>  		__set_current_state(TASK_RUNNING);
>  
> @@ -770,8 +769,6 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
>  		goto out_found;
>  	}
>  
> -	if (!time_left)
> -		percpu_counter_inc(&pool->sp_threads_timedout);
>  	if (kthread_should_stop())
>  		return NULL;
>  	percpu_counter_inc(&pool->sp_threads_no_work);
> @@ -856,7 +853,7 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
>   * organised not to touch any cachelines in the shared svc_serv
>   * structure, only cachelines in the local svc_pool.
>   */
> -void svc_recv(struct svc_rqst *rqstp, long timeout)
> +void svc_recv(struct svc_rqst *rqstp)
>  {
>  	struct svc_xprt		*xprt = NULL;
>  	struct svc_serv		*serv = rqstp->rq_server;
> @@ -870,7 +867,7 @@ void svc_recv(struct svc_rqst *rqstp, long timeout)
>  	if (kthread_should_stop())
>  		goto out;
>  
> -	xprt = svc_get_next_xprt(rqstp, timeout);
> +	xprt = svc_get_next_xprt(rqstp);
>  	if (!xprt)
>  		goto out;
>  
> @@ -1437,14 +1434,14 @@ static int svc_pool_stats_show(struct seq_file *m, void *p)
>  		return 0;
>  	}
>  
> -	seq_printf(m, "%u %llu %llu %llu %llu %llu %llu\n",
> -		pool->sp_id,
> -		percpu_counter_sum_positive(&pool->sp_messages_arrived),
> -		percpu_counter_sum_positive(&pool->sp_sockets_queued),
> -		percpu_counter_sum_positive(&pool->sp_threads_woken),
> -		percpu_counter_sum_positive(&pool->sp_threads_timedout),
> -		percpu_counter_sum_positive(&pool->sp_threads_starved),
> -		percpu_counter_sum_positive(&pool->sp_threads_no_work));
> +	seq_printf(m, "%u %llu %llu %llu 0 %llu %llu\n",
> +		   pool->sp_id,
> +		   percpu_counter_sum_positive(&pool->sp_messages_arrived),
> +		   percpu_counter_sum_positive(&pool->sp_sockets_queued),
> +		   percpu_counter_sum_positive(&pool->sp_threads_woken),
> +		   /* prevously pool->sp_threads_timedout */
> +		   percpu_counter_sum_positive(&pool->sp_threads_starved),
> +		   percpu_counter_sum_positive(&pool->sp_threads_no_work));
>  
>  	return 0;
>  }
> 
> 

More simplifications. I like it!

Reviewed-by: Jeff Layton <jlayton@kernel.org>