SUNRPC: Add a separate spinlock to protect the RPC request receive list

This further reduces contention with the transport_lock, and allows us
to convert to using a non-bh-safe spinlock, since the list is now never
accessed from a bh context.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

6 files changed, 41 insertions, 31 deletions

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 65b9e0224753..a97e6de5f9f2 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -232,6 +232,7 @@ struct rpc_xprt {
          */
         spinlock_t              transport_lock; /* lock transport info */
         spinlock_t              reserve_lock;   /* lock slot table */
+        spinlock_t              recv_lock;      /* lock receive list */
         u32                     xid;            /* Next XID value to use */
         struct rpc_task *       snd_task;       /* Task blocked in send */
         struct svc_xprt         *bc_xprt;       /* NFSv4.1 backchannel */
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 2b720fa35c4f..272063ca81e8 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1001,7 +1001,7 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 
         if (!bc_xprt)
                 return -EAGAIN;
-        spin_lock_bh(&bc_xprt->transport_lock);
+        spin_lock(&bc_xprt->recv_lock);
         req = xprt_lookup_rqst(bc_xprt, xid);
         if (!req)
                 goto unlock_notfound;
@@ -1019,7 +1019,7 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
         memcpy(dst->iov_base, src->iov_base, src->iov_len);
         xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
         rqstp->rq_arg.len = 0;
-        spin_unlock_bh(&bc_xprt->transport_lock);
+        spin_unlock(&bc_xprt->recv_lock);
         return 0;
 unlock_notfound:
         printk(KERN_NOTICE
@@ -1028,7 +1028,7 @@ unlock_notfound:
                 __func__, ntohl(calldir),
                 bc_xprt, ntohl(xid));
 unlock_eagain:
-        spin_unlock_bh(&bc_xprt->transport_lock);
+        spin_unlock(&bc_xprt->recv_lock);
         return -EAGAIN;
 }
 
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 3eb9ec16eec4..2af189c5ac3e 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -872,17 +872,17 @@ void xprt_unpin_rqst(struct rpc_rqst *req)
 }
 
 static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)
-__must_hold(&req->rq_xprt->transport_lock)
+__must_hold(&req->rq_xprt->recv_lock)
 {
         struct rpc_task *task = req->rq_task;
         
         if (task && test_bit(RPC_TASK_MSG_RECV, &task->tk_runstate)) {
-                spin_unlock_bh(&req->rq_xprt->transport_lock);
+                spin_unlock(&req->rq_xprt->recv_lock);
                 set_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
                 wait_on_bit(&task->tk_runstate, RPC_TASK_MSG_RECV,
                                 TASK_UNINTERRUPTIBLE);
                 clear_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
-                spin_lock_bh(&req->rq_xprt->transport_lock);
+                spin_lock(&req->rq_xprt->recv_lock);
         }
 }
 
@@ -1008,13 +1008,13 @@ void xprt_transmit(struct rpc_task *task)
                         /*
                          * Add to the list only if we're expecting a reply
                          */
-                        spin_lock_bh(&xprt->transport_lock);
                         /* Update the softirq receive buffer */
                         memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
                                         sizeof(req->rq_private_buf));
                         /* Add request to the receive list */
+                        spin_lock(&xprt->recv_lock);
                         list_add_tail(&req->rq_list, &xprt->recv);
-                        spin_unlock_bh(&xprt->transport_lock);
+                        spin_unlock(&xprt->recv_lock);
                         xprt_reset_majortimeo(req);
                         /* Turn off autodisconnect */
                         del_singleshot_timer_sync(&xprt->timer);
@@ -1329,15 +1329,18 @@ void xprt_release(struct rpc_task *task)
                 task->tk_ops->rpc_count_stats(task, task->tk_calldata);
         else if (task->tk_client)
                 rpc_count_iostats(task, task->tk_client->cl_metrics);
+        spin_lock(&xprt->recv_lock);
+        if (!list_empty(&req->rq_list)) {
+                list_del(&req->rq_list);
+                xprt_wait_on_pinned_rqst(req);
+        }
+        spin_unlock(&xprt->recv_lock);
         spin_lock_bh(&xprt->transport_lock);
         xprt->ops->release_xprt(xprt, task);
         if (xprt->ops->release_request)
                 xprt->ops->release_request(task);
-        if (!list_empty(&req->rq_list))
-                list_del(&req->rq_list);
         xprt->last_used = jiffies;
         xprt_schedule_autodisconnect(xprt);
-        xprt_wait_on_pinned_rqst(req);
         spin_unlock_bh(&xprt->transport_lock);
         if (req->rq_buffer)
                 xprt->ops->buf_free(task);
@@ -1361,6 +1364,7 @@ static void xprt_init(struct rpc_xprt *xprt, struct net *net)
 
         spin_lock_init(&xprt->transport_lock);
         spin_lock_init(&xprt->reserve_lock);
+        spin_lock_init(&xprt->recv_lock);
 
         INIT_LIST_HEAD(&xprt->free);
         INIT_LIST_HEAD(&xprt->recv);
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index ca4d6e4528f3..dfa748a0c8de 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -1051,7 +1051,7 @@ rpcrdma_reply_handler(struct work_struct *work)
          * RPC completion while holding the transport lock to ensure
          * the rep, rqst, and rq_task pointers remain stable.
          */
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         rqst = xprt_lookup_rqst(xprt, headerp->rm_xid);
         if (!rqst)
                 goto out_norqst;
@@ -1136,7 +1136,7 @@ out:
                 xprt_release_rqst_cong(rqst->rq_task);
 
         xprt_complete_rqst(rqst->rq_task, status);
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
         dprintk("RPC:       %s: xprt_complete_rqst(0x%p, 0x%p, %d)\n",
                 __func__, xprt, rqst, status);
         return;
@@ -1187,12 +1187,12 @@ out_rdmaerr:
         r_xprt->rx_stats.bad_reply_count++;
         goto out;
 
-/* The req was still available, but by the time the transport_lock
+/* The req was still available, but by the time the recv_lock
  * was acquired, the rqst and task had been released. Thus the RPC
  * has already been terminated.
  */
 out_norqst:
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
         rpcrdma_buffer_put(req);
         dprintk("RPC:       %s: race, no rqst left for req %p\n",
                 __func__, req);
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index c676ed0efb5a..0d574cda242d 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -52,7 +52,7 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
         if (src->iov_len < 24)
                 goto out_shortreply;
 
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         req = xprt_lookup_rqst(xprt, xid);
         if (!req)
                 goto out_notfound;
@@ -69,17 +69,20 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
         else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
                 credits = r_xprt->rx_buf.rb_bc_max_requests;
 
+        spin_lock_bh(&xprt->transport_lock);
         cwnd = xprt->cwnd;
         xprt->cwnd = credits << RPC_CWNDSHIFT;
         if (xprt->cwnd > cwnd)
                 xprt_release_rqst_cong(req->rq_task);
+        spin_unlock_bh(&xprt->transport_lock);
+
 
         ret = 0;
         xprt_complete_rqst(req->rq_task, rcvbuf->len);
         rcvbuf->len = 0;
 
 out_unlock:
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
 out:
         return ret;
 
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index a344bea15fc7..2b918137aaa0 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -969,12 +969,12 @@ static void xs_local_data_read_skb(struct rpc_xprt *xprt,
                 return;
 
         /* Look up and lock the request corresponding to the given XID */
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         rovr = xprt_lookup_rqst(xprt, *xp);
         if (!rovr)
                 goto out_unlock;
         xprt_pin_rqst(rovr);
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
         task = rovr->rq_task;
 
         copied = rovr->rq_private_buf.buflen;
@@ -983,16 +983,16 @@ static void xs_local_data_read_skb(struct rpc_xprt *xprt,
 
         if (xs_local_copy_to_xdr(&rovr->rq_private_buf, skb)) {
                 dprintk("RPC:       sk_buff copy failed\n");
-                spin_lock_bh(&xprt->transport_lock);
+                spin_lock(&xprt->recv_lock);
                 goto out_unpin;
         }
 
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         xprt_complete_rqst(task, copied);
 out_unpin:
         xprt_unpin_rqst(rovr);
  out_unlock:
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
 }
 
 static void xs_local_data_receive(struct sock_xprt *transport)
@@ -1055,12 +1055,12 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
                 return;
 
         /* Look up and lock the request corresponding to the given XID */
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         rovr = xprt_lookup_rqst(xprt, *xp);
         if (!rovr)
                 goto out_unlock;
         xprt_pin_rqst(rovr);
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
         task = rovr->rq_task;
 
         if ((copied = rovr->rq_private_buf.buflen) > repsize)
@@ -1069,7 +1069,7 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
         /* Suck it into the iovec, verify checksum if not done by hw. */
         if (csum_partial_copy_to_xdr(&rovr->rq_private_buf, skb)) {
                 __UDPX_INC_STATS(sk, UDP_MIB_INERRORS);
-                spin_lock_bh(&xprt->transport_lock);
+                spin_lock(&xprt->recv_lock);
                 goto out_unpin;
         }
 
@@ -1077,11 +1077,13 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
 
         spin_lock_bh(&xprt->transport_lock);
         xprt_adjust_cwnd(xprt, task, copied);
+        spin_unlock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         xprt_complete_rqst(task, copied);
 out_unpin:
         xprt_unpin_rqst(rovr);
  out_unlock:
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
 }
 
 static void xs_udp_data_receive(struct sock_xprt *transport)
@@ -1344,24 +1346,24 @@ static inline int xs_tcp_read_reply(struct rpc_xprt *xprt,
         dprintk("RPC:       read reply XID %08x\n", ntohl(transport->tcp_xid));
 
         /* Find and lock the request corresponding to this xid */
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         req = xprt_lookup_rqst(xprt, transport->tcp_xid);
         if (!req) {
                 dprintk("RPC:       XID %08x request not found!\n",
                                 ntohl(transport->tcp_xid));
-                spin_unlock_bh(&xprt->transport_lock);
+                spin_unlock(&xprt->recv_lock);
                 return -1;
         }
         xprt_pin_rqst(req);
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
 
         xs_tcp_read_common(xprt, desc, req);
 
-        spin_lock_bh(&xprt->transport_lock);
+        spin_lock(&xprt->recv_lock);
         if (!(transport->tcp_flags & TCP_RCV_COPY_DATA))
                 xprt_complete_rqst(req->rq_task, transport->tcp_copied);
         xprt_unpin_rqst(req);
-        spin_unlock_bh(&xprt->transport_lock);
+        spin_unlock(&xprt->recv_lock);
         return 0;
 }