[PATCH] sunrpc: wake up SOFTCONN tasks when a connection error happens.

NeilBrown
2011-11-07T04:07:12Z

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hi all,
It being over a year since I last raised this I thought it might be time to
try again.

The problem is that an NFSv4 mount request (the default) to an unrouteable
server results in a 3 minute timeout instead of an instant failure.

This is easy to test by simply removing your default route then trying to
mount something outside your local network.

This patch causes any SOFTCONN task to be woken up as soon as a connection
error occurs so that it can fail promptly. The failure reasons gets passed
back and as it is not ETIMEDOUT it causes immediate failure.

Is this a reasonable approach?

Thanks,
NeilBrown

From a1aea8fc3977ffa9951c3d7f27dbb1905e5f560f Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Mon, 7 Nov 2011 15:00:17 +1100
Subject: [PATCH] sunrpc: wake up SOFTCONN tasks when a connection error
happens.

A 'SOFTCONN' task should fail if there is an error or a major timeout
during connection.

However errors are currently converted into a timeout (60seconds for
TCP) which is treated as a minor timeout and 3 of these are required
before failure.

The result of this is that if you try to mount an NFSv4 filesystem
(which doesn't require rpcbind and the failure modes that provides)
from a server which you do not have a route to (an so get
NETUNREACHABLE), you have an unnecessary 3 minutes timeout.

So when ENETUNREACH is reported for a connection - or other errors
which are fatal, wake up any SOFTCONN tasks with that error - rather
than letting them wait 60 seconds and then generate ETIMEDOUT.

This causes the above mentioned mount attempt to fail instantly.

Signed-off-by: NeilBrown <neilb@suse.de>
---
include/linux/sunrpc/sched.h | 1 +
net/sunrpc/sched.c | 29 +++++++++++++++++++++++++++++
net/sunrpc/xprtsock.c | 6 +++++-
3 files changed, 35 insertions(+), 1 deletions(-)

diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index e775689..b85451b 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -236,6 +236,7 @@ void rpc_wake_up_queued_task(struct rpc_wait_queue *,
void rpc_wake_up(struct rpc_wait_queue *);
struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *);
void rpc_wake_up_status(struct rpc_wait_queue *, int);
+void rpc_wake_up_softconn_status(struct rpc_wait_queue *, int);
int rpc_queue_empty(struct rpc_wait_queue *);
void rpc_delay(struct rpc_task *, unsigned long);
void * rpc_malloc(struct rpc_task *, size_t);
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index d12ffa5..d92000a 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -543,6 +543,35 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
}
EXPORT_SYMBOL_GPL(rpc_wake_up_status);

+/**
+ * rpc_wake_up_softconn_status - wake up all SOFTCONN rpc_tasks and set their
+ * status value.
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ * @status: status value to set
+ *
+ * Grabs queue->lock
+ */
+void rpc_wake_up_softconn_status(struct rpc_wait_queue *queue, int status)
+{
+ struct rpc_task *task, *next;
+ struct list_head *head;
+
+ spin_lock_bh(&queue->lock);
+ head = &queue->tasks[queue->maxpriority];
+ for (;;) {
+ list_for_each_entry_safe(task, next, head, u.tk_wait.list)
+ if (RPC_IS_SOFTCONN(task)) {
+ task->tk_status = status;
+ rpc_wake_up_task_queue_locked(queue, task);
+ }
+ if (head == &queue->tasks[0])
+ break;
+ head--;
+ }
+ spin_unlock_bh(&queue->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up_softconn_status);
+
static void __rpc_queue_timer_fn(unsigned long ptr)
{
struct rpc_wait_queue *queue = (struct rpc_wait_queue *)ptr;
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index d7f97ef..02c683b 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2158,7 +2158,11 @@ static void xs_tcp_setup_socket(struct work_struct *work)
case -ECONNREFUSED:
case -ECONNRESET:
case -ENETUNREACH:
- /* retry with existing socket, after a delay */
+ /* Retry with existing socket after a delay, except
+ * for SOFTCONN tasks which fail. */
+ xprt_clear_connecting(xprt);
+ rpc_wake_up_softconn_status(&xprt->pending, status);
+ return;
case 0:
case -EINPROGRESS:
case -EALREADY:
--
1.7.7

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