SUNRPC: change the back-channel queue to lwq

This removes the need to store and update back-links in the list.
It also remove the need for the _bh version of spin_lock().

Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: neilbrown

include/linux/sunrpc/svc.h

@@ -90,10 +90,9 @@ struct svc_serv {
 	int			(*sv_threadfn)(void *data);
 
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
-	struct list_head	sv_cb_list;	/* queue for callback requests
+	struct lwq		sv_cb_list;	/* queue for callback requests
 						 * that arrive over the same
 						 * connection */
-	spinlock_t		sv_cb_lock;	/* protects the svc_cb_list */
 	bool			sv_bc_enabled;	/* service uses backchannel */
 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
 };

include/linux/sunrpc/xprt.h

@@ -57,6 +57,7 @@ struct xprt_class;
 struct seq_file;
 struct svc_serv;
 struct net;
+#include <linux/lwq.h>
 
 /*
  * This describes a complete RPC request
@@ -121,7 +122,7 @@ struct rpc_rqst {
 	int			rq_ntrans;
 
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
-	struct list_head	rq_bc_list;	/* Callback service list */
+	struct lwq_node		rq_bc_list;	/* Callback service list */
 	unsigned long		rq_bc_pa_state;	/* Backchannel prealloc state */
 	struct list_head	rq_bc_pa_list;	/* Backchannel prealloc list */
 #endif /* CONFIG_SUNRPC_BACKCHANEL */

net/sunrpc/backchannel_rqst.c

@@ -83,7 +83,6 @@ static struct rpc_rqst *xprt_alloc_bc_req(struct rpc_xprt *xprt)
 		return NULL;
 
 	req->rq_xprt = xprt;
-	INIT_LIST_HEAD(&req->rq_bc_list);
 
 	/* Preallocate one XDR receive buffer */
 	if (xprt_alloc_xdr_buf(&req->rq_rcv_buf, gfp_flags) < 0) {
@@ -367,8 +366,6 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
 
 	dprintk("RPC:       add callback request to list\n");
 	xprt_get(xprt);
-	spin_lock(&bc_serv->sv_cb_lock);
-	list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
-	spin_unlock(&bc_serv->sv_cb_lock);
+	lwq_enqueue(&req->rq_bc_list, &bc_serv->sv_cb_list);
 	svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
 }

net/sunrpc/svc.c

@@ -438,8 +438,7 @@ EXPORT_SYMBOL_GPL(svc_bind);
 static void
 __svc_init_bc(struct svc_serv *serv)
 {
-	INIT_LIST_HEAD(&serv->sv_cb_list);
-	spin_lock_init(&serv->sv_cb_lock);
+	lwq_init(&serv->sv_cb_list);
 }
 #else
 static void

net/sunrpc/svc_xprt.c

@@ -705,7 +705,7 @@ svc_thread_should_sleep(struct svc_rqst *rqstp)
 
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
 	if (svc_is_backchannel(rqstp)) {
-		if (!list_empty(&rqstp->rq_server->sv_cb_list))
+		if (!lwq_empty(&rqstp->rq_server->sv_cb_list))
 			return false;
 	}
 #endif
@@ -878,18 +878,12 @@ void svc_recv(struct svc_rqst *rqstp)
 		struct svc_serv *serv = rqstp->rq_server;
 		struct rpc_rqst *req;
 
-		spin_lock_bh(&serv->sv_cb_lock);
-		req = list_first_entry_or_null(&serv->sv_cb_list,
-					       struct rpc_rqst, rq_bc_list);
+		req = lwq_dequeue(&serv->sv_cb_list,
+				  struct rpc_rqst, rq_bc_list);
 		if (req) {
-			list_del(&req->rq_bc_list);
-			spin_unlock_bh(&serv->sv_cb_lock);
 			svc_thread_wake_next(rqstp);
-
 			svc_process_bc(req, rqstp);
-			return;
 		}
-		spin_unlock_bh(&serv->sv_cb_lock);
 	}
 #endif
 }

net/sunrpc/xprtrdma/backchannel.c

@@ -263,9 +263,7 @@ void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 	/* Queue rqst for ULP's callback service */
 	bc_serv = xprt->bc_serv;
 	xprt_get(xprt);
-	spin_lock(&bc_serv->sv_cb_lock);
-	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
-	spin_unlock(&bc_serv->sv_cb_lock);
+	lwq_enqueue(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
 
 	svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);