[PATCH 6/6] sunrpc: introduce possibility that requested number of threads is different from actual

[NeilBrown <neilb@suse.de>]

New fields sp_nractual and sv_nractual track how many actual threads are
running.  sp_nrhtreads and sv_nrthreads will be the number that were
explicitly request.  Currently nractually == nrthreads.

sv_nractual is used for sizing UDP incoming socket space - in the rare
case that UDP is used.  This is because each thread might need to keep a
request in the skbs.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 include/linux/sunrpc/svc.h |  6 ++++--
 net/sunrpc/svc.c           | 22 +++++++++++++++-------
 net/sunrpc/svcsock.c       |  2 +-
 3 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 9d288a673705..3f2c90061b4a 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -36,7 +36,8 @@
 struct svc_pool {
 	unsigned int		sp_id;		/* pool id; also node id on NUMA */
 	struct lwq		sp_xprts;	/* pending transports */
-	unsigned int		sp_nrthreads;	/* # of threads in pool */
+	unsigned int		sp_nrthreads;	/* # of threads requested for pool */
+	unsigned int		sp_nractual;	/* # of threads running */
 	struct list_head	sp_all_threads;	/* all server threads */
 	struct llist_head	sp_idle_threads; /* idle server threads */
 
@@ -71,7 +72,8 @@ struct svc_serv {
 	struct svc_stat *	sv_stats;	/* RPC statistics */
 	spinlock_t		sv_lock;
 	unsigned int		sv_nprogs;	/* Number of sv_programs */
-	unsigned int		sv_nrthreads;	/* # of server threads */
+	unsigned int		sv_nrthreads;	/* # of server threads requested*/
+	unsigned int		sv_nractual;	/* # of running threads */
 	unsigned int		sv_max_payload;	/* datagram payload size */
 	unsigned int		sv_max_mesg;	/* max_payload + 1 page for overheads */
 	unsigned int		sv_xdrsize;	/* XDR buffer size */
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index bd4f02b34f44..d332f9d3d875 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -781,8 +781,12 @@ svc_pool_victim(struct svc_serv *serv, struct svc_pool *target_pool,
 	}
 
 	if (pool && pool->sp_nrthreads) {
-		set_bit(SP_VICTIM_REMAINS, &pool->sp_flags);
-		set_bit(SP_NEED_VICTIM, &pool->sp_flags);
+		if (pool->sp_nrthreads <= pool->sp_nractual) {
+			set_bit(SP_VICTIM_REMAINS, &pool->sp_flags);
+			set_bit(SP_NEED_VICTIM, &pool->sp_flags);
+			pool->sp_nractual -= 1;
+			serv->sv_nractual -= 1;
+		}
 		return pool;
 	}
 	return NULL;
@@ -803,6 +807,12 @@ svc_start_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
 		chosen_pool = svc_pool_next(serv, pool, &state);
 		node = svc_pool_map_get_node(chosen_pool->sp_id);
 
+		serv->sv_nrthreads += 1;
+		chosen_pool->sp_nrthreads += 1;
+
+		if (chosen_pool->sp_nrthreads <= chosen_pool->sp_nractual)
+			continue;
+
 		rqstp = svc_prepare_thread(serv, chosen_pool, node);
 		if (!rqstp)
 			return -ENOMEM;
@@ -812,8 +822,8 @@ svc_start_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
 			svc_exit_thread(rqstp);
 			return PTR_ERR(task);
 		}
-		serv->sv_nrthreads += 1;
-		chosen_pool->sp_nrthreads += 1;
+		serv->sv_nractual += 1;
+		chosen_pool->sp_nractual += 1;
 
 		rqstp->rq_task = task;
 		if (serv->sv_nrpools > 1)
@@ -850,6 +860,7 @@ svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
 			    TASK_IDLE);
 		nrservs++;
 	} while (nrservs < 0);
+	svc_sock_update_bufs(serv);
 	return 0;
 }
 
@@ -955,13 +966,10 @@ void svc_rqst_release_pages(struct svc_rqst *rqstp)
 void
 svc_exit_thread(struct svc_rqst *rqstp)
 {
-	struct svc_serv	*serv = rqstp->rq_server;
 	struct svc_pool	*pool = rqstp->rq_pool;
 
 	list_del_rcu(&rqstp->rq_all);
 
-	svc_sock_update_bufs(serv);
-
 	svc_rqst_free(rqstp);
 
 	clear_and_wake_up_bit(SP_VICTIM_REMAINS, &pool->sp_flags);
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 825ec5357691..191dbc648bd0 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -588,7 +588,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	     * provides an upper bound on the number of threads
 	     * which will access the socket.
 	     */
-	    svc_sock_setbufsize(svsk, serv->sv_nrthreads + 3);
+	    svc_sock_setbufsize(svsk, serv->sv_nractual + 3);
 
 	clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 	err = kernel_recvmsg(svsk->sk_sock, &msg, NULL,
-- 
2.46.0