SUNRPC: use lwq for sp_sockets - renamed to sp_xprts

lwq avoids using back pointers in lists, and uses less locking.
This introduces a new spinlock, but the other one will be removed in a
future patch.

For svc_clean_up_xprts(), we now dequeue the entire queue, walk it to
remove and process the xprts that need cleaning up, then re-enqueue the
remaining queue.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/linux/sunrpc/svc.h

@@ -17,6 +17,7 @@
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/auth.h>
 #include <linux/sunrpc/svcauth.h>
+#include <linux/lwq.h>
 #include <linux/wait.h>
 #include <linux/mm.h>
 #include <linux/pagevec.h>
@@ -34,7 +35,7 @@
 struct svc_pool {
 	unsigned int		sp_id;	    	/* pool id; also node id on NUMA */
 	spinlock_t		sp_lock;	/* protects all fields */
-	struct list_head	sp_sockets;	/* pending sockets */
+	struct lwq		sp_xprts;	/* pending transports */
 	unsigned int		sp_nrthreads;	/* # of threads in pool */
 	struct list_head	sp_all_threads;	/* all server threads */
 	struct llist_head	sp_idle_threads; /* idle server threads */

include/linux/sunrpc/svc_xprt.h

@@ -54,7 +54,7 @@ struct svc_xprt {
 	const struct svc_xprt_ops *xpt_ops;
 	struct kref		xpt_ref;
 	struct list_head	xpt_list;
-	struct list_head	xpt_ready;
+	struct lwq_node		xpt_ready;
 	unsigned long		xpt_flags;
 
 	struct svc_serv		*xpt_server;	/* service for transport */

net/sunrpc/svc.c

@@ -508,7 +508,7 @@ __svc_create(struct svc_program *prog, unsigned int bufsize, int npools,
 				i, serv->sv_name);
 
 		pool->sp_id = i;
-		INIT_LIST_HEAD(&pool->sp_sockets);
+		lwq_init(&pool->sp_xprts);
 		INIT_LIST_HEAD(&pool->sp_all_threads);
 		init_llist_head(&pool->sp_idle_threads);
 		spin_lock_init(&pool->sp_lock);

net/sunrpc/svc_xprt.c

@@ -201,7 +201,6 @@ void svc_xprt_init(struct net *net, struct svc_xprt_class *xcl,
 	kref_init(&xprt->xpt_ref);
 	xprt->xpt_server = serv;
 	INIT_LIST_HEAD(&xprt->xpt_list);
-	INIT_LIST_HEAD(&xprt->xpt_ready);
 	INIT_LIST_HEAD(&xprt->xpt_deferred);
 	INIT_LIST_HEAD(&xprt->xpt_users);
 	mutex_init(&xprt->xpt_mutex);
@@ -472,9 +471,7 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 	pool = svc_pool_for_cpu(xprt->xpt_server);
 
 	percpu_counter_inc(&pool->sp_sockets_queued);
-	spin_lock_bh(&pool->sp_lock);
-	list_add_tail(&xprt->xpt_ready, &pool->sp_sockets);
-	spin_unlock_bh(&pool->sp_lock);
+	lwq_enqueue(&xprt->xpt_ready, &pool->sp_xprts);
 
 	svc_pool_wake_idle_thread(pool);
 }
@@ -487,18 +484,9 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
 {
 	struct svc_xprt	*xprt = NULL;
 
-	if (list_empty(&pool->sp_sockets))
-		goto out;
-
-	spin_lock_bh(&pool->sp_lock);
-	if (likely(!list_empty(&pool->sp_sockets))) {
-		xprt = list_first_entry(&pool->sp_sockets,
-					struct svc_xprt, xpt_ready);
-		list_del_init(&xprt->xpt_ready);
+	xprt = lwq_dequeue(&pool->sp_xprts, struct svc_xprt, xpt_ready);
+	if (xprt)
 		svc_xprt_get(xprt);
-	}
-	spin_unlock_bh(&pool->sp_lock);
-out:
 	return xprt;
 }
 
@@ -708,7 +696,7 @@ svc_thread_should_sleep(struct svc_rqst *rqstp)
 		return false;
 
 	/* was a socket queued? */
-	if (!list_empty(&pool->sp_sockets))
+	if (!lwq_empty(&pool->sp_xprts))
 		return false;
 
 	/* are we shutting down? */
@@ -1050,7 +1038,6 @@ static void svc_delete_xprt(struct svc_xprt *xprt)
 
 	spin_lock_bh(&serv->sv_lock);
 	list_del_init(&xprt->xpt_list);
-	WARN_ON_ONCE(!list_empty(&xprt->xpt_ready));
 	if (test_bit(XPT_TEMP, &xprt->xpt_flags))
 		serv->sv_tmpcnt--;
 	spin_unlock_bh(&serv->sv_lock);
@@ -1101,36 +1088,26 @@ static int svc_close_list(struct svc_serv *serv, struct list_head *xprt_list, st
 	return ret;
 }
 
-static struct svc_xprt *svc_dequeue_net(struct svc_serv *serv, struct net *net)
+static void svc_clean_up_xprts(struct svc_serv *serv, struct net *net)
 {
-	struct svc_pool *pool;
 	struct svc_xprt *xprt;
-	struct svc_xprt *tmp;
 	int i;
 
 	for (i = 0; i < serv->sv_nrpools; i++) {
-		pool = &serv->sv_pools[i];
-
-		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);
-			return xprt;
+		struct svc_pool *pool = &serv->sv_pools[i];
+		struct llist_node *q, **t1, *t2;
+
+		q = lwq_dequeue_all(&pool->sp_xprts);
+		lwq_for_each_safe(xprt, t1, t2, &q, xpt_ready) {
+			if (xprt->xpt_net == net) {
+				set_bit(XPT_CLOSE, &xprt->xpt_flags);
+				svc_delete_xprt(xprt);
+				xprt = NULL;
+			}
 		}
-		spin_unlock_bh(&pool->sp_lock);
-	}
-	return NULL;
-}
 
-static void svc_clean_up_xprts(struct svc_serv *serv, struct net *net)
-{
-	struct svc_xprt *xprt;
-
-	while ((xprt = svc_dequeue_net(serv, net))) {
-		set_bit(XPT_CLOSE, &xprt->xpt_flags);
-		svc_delete_xprt(xprt);
+		if (q)
+			lwq_enqueue_batch(q, &pool->sp_xprts);
 	}
 }