SUNRPC: Run rpc timeout functions as callbacks instead of in softirqs

An audit of the current RPC timeout functions shows that they don't really
ever need to run in the softirq context. As long as the softirq is
able to signal that the wakeup is due to a timeout (which it can do by
setting task->tk_status to -ETIMEDOUT) then the callback functions can just
run as standard task->tk_callback functions (in the rpciod/process
context).

The only possible border-line case would be xprt_timer() for the case of
UDP, when the callback is used to reduce the size of the transport
congestion window. In testing, however, the effect of moving that update
to a callback would appear to be minor.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 15 insertions, 13 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 6e2772217e55..9bf118c54316 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -188,9 +188,9 @@ out_sleep:
         task->tk_timeout = 0;
         task->tk_status = -EAGAIN;
         if (req && req->rq_ntrans)
-                rpc_sleep_on(&xprt->resend, task, NULL, NULL);
+                rpc_sleep_on(&xprt->resend, task, NULL);
         else
-                rpc_sleep_on(&xprt->sending, task, NULL, NULL);
+                rpc_sleep_on(&xprt->sending, task, NULL);
         return 0;
 }
 EXPORT_SYMBOL_GPL(xprt_reserve_xprt);
@@ -238,9 +238,9 @@ out_sleep:
         task->tk_timeout = 0;
         task->tk_status = -EAGAIN;
         if (req && req->rq_ntrans)
-                rpc_sleep_on(&xprt->resend, task, NULL, NULL);
+                rpc_sleep_on(&xprt->resend, task, NULL);
         else
-                rpc_sleep_on(&xprt->sending, task, NULL, NULL);
+                rpc_sleep_on(&xprt->sending, task, NULL);
         return 0;
 }
 EXPORT_SYMBOL_GPL(xprt_reserve_xprt_cong);
@@ -453,7 +453,7 @@ void xprt_wait_for_buffer_space(struct rpc_task *task)
         struct rpc_xprt *xprt = req->rq_xprt;
 
         task->tk_timeout = req->rq_timeout;
-        rpc_sleep_on(&xprt->pending, task, NULL, NULL);
+        rpc_sleep_on(&xprt->pending, task, NULL);
 }
 EXPORT_SYMBOL_GPL(xprt_wait_for_buffer_space);
 
@@ -652,7 +652,7 @@ void xprt_connect(struct rpc_task *task)
                         task->tk_rqstp->rq_bytes_sent = 0;
 
                 task->tk_timeout = xprt->connect_timeout;
-                rpc_sleep_on(&xprt->pending, task, xprt_connect_status, NULL);
+                rpc_sleep_on(&xprt->pending, task, xprt_connect_status);
                 xprt->stat.connect_start = jiffies;
                 xprt->ops->connect(task);
         }
@@ -769,15 +769,17 @@ static void xprt_timer(struct rpc_task *task)
         struct rpc_rqst *req = task->tk_rqstp;
         struct rpc_xprt *xprt = req->rq_xprt;
 
+        if (task->tk_status != -ETIMEDOUT)
+                return;
         dprintk("RPC: %5u xprt_timer\n", task->tk_pid);
 
-        spin_lock(&xprt->transport_lock);
+        spin_lock_bh(&xprt->transport_lock);
         if (!req->rq_received) {
                 if (xprt->ops->timer)
                         xprt->ops->timer(task);
-                task->tk_status = -ETIMEDOUT;
-        }
-        spin_unlock(&xprt->transport_lock);
+        } else
+                task->tk_status = 0;
+        spin_unlock_bh(&xprt->transport_lock);
 }
 
 /**
@@ -862,7 +864,7 @@ void xprt_transmit(struct rpc_task *task)
                 if (!xprt_connected(xprt))
                         task->tk_status = -ENOTCONN;
                 else if (!req->rq_received)
-                        rpc_sleep_on(&xprt->pending, task, NULL, xprt_timer);
+                        rpc_sleep_on(&xprt->pending, task, xprt_timer);
                 spin_unlock_bh(&xprt->transport_lock);
                 return;
         }
@@ -873,7 +875,7 @@ void xprt_transmit(struct rpc_task *task)
          */
         task->tk_status = status;
         if (status == -ECONNREFUSED)
-                rpc_sleep_on(&xprt->sending, task, NULL, NULL);
+                rpc_sleep_on(&xprt->sending, task, NULL);
 }
 
 static inline void do_xprt_reserve(struct rpc_task *task)
@@ -893,7 +895,7 @@ static inline void do_xprt_reserve(struct rpc_task *task)
         dprintk("RPC:       waiting for request slot\n");
         task->tk_status = -EAGAIN;
         task->tk_timeout = 0;
-        rpc_sleep_on(&xprt->backlog, task, NULL, NULL);
+        rpc_sleep_on(&xprt->backlog, task, NULL);
 }
 
 /**