Re: NFS client errors with 2.5.74?

Re: NFS client errors with 2.5.74?

[Jamie Lokier]

>      >       kernel: nfs: server 192.168.1.1 not responding, timed out

Trond Myklebust wrote:
> I can never guarantee you perfect service with soft mounts (a 5 second
> network patition/server congestion is all it takes)

There is _no_ congestion to speak of: I type "ls directory" and it
returns EIO apparently immediately, from an otherwise idle network and
unloaded server.

The "server 192.168.1.1 not responding, timed out" message also
appears immediately in this case - there is no 5 second delay.

There is no 0.7 second delay either (the default value of "timeo"
according to nfs(5)).  So the retransmission logic is buggered.

> Sigh... I hate soft mounts...  Have I said that before? 8-)

If I switch to a hard mount ("hard,intr") the EIO errors go away.

However, the protocol problem remains: multiple READDIRPLUS calls with
the same xid in a fraction of a second.  Note: there is no 0.7 second
delay between these packets.  According to Ethereal, it is between
0.01 and 0.1 seconds between duplicate requests.

There seems to be a transition from a state where calls with duplicate
xids are rare (but they do occur), to one where they occur on nearly
every request.

I have 768MB of RAM on the client, so I checked whether RAM being
filled makes a difference.  Not really.

After mounting, if I do "ls -lR" then I see that duplicate xids are
rare for a while, then they become common.  In this state, I still
have 400MB free (i.e. not even filled clean pagecache pages), so it is
not an absolute shortage of RAM which triggers this, but something else.

I suspect the request timeout logic is buggered, and sending retries
too quickly - 0.01 to 0.1 seconds rather than 0.7 upwards.  It would
also explain why "soft" is failing quickly: if the timeout logic
thinks it has already sent the maximum number of retries in a very
short time, it will count it as a timeout even though the server is
quite fast in responding.

It's interesting that this state can be reached even when the network,
client and server are idle and I try "ls directory" for some uncached
directory.  This shows it's not purely a question of congestion, but
that even a fast response is not good enough.

-- Jamie

Re: NFS client errors with 2.5.74?

[Jamie Lokier]

Trond Myklebust wrote:
> >>>>> " " == Jamie Lokier <jamie@shareable.org> writes:
> 
> 
>      > There is no 0.7 second delay either (the default value of
>      > "timeo" according to nfs(5)).  So the retransmission logic is
>      > buggered.
> 
> No. manpage is buggered. We use round trip time estimation now...
> 
> 
>      > However, the protocol problem remains: multiple READDIRPLUS
>      > calls with the same xid in a fraction of a second.  Note: there
>      > is no 0.7 second delay between these packets.  According to
>      > Ethereal, it is between
>      > 0.01 and 0.1 seconds between duplicate requests.
> 
> Yup. That's what the RTO does...

So the problem state arises when the round trip time converges on some
value which is too small?  And in this state, "soft" returns EIO
within some ridiculously small timeout?

It is definitely too small because I see that the bulk of readdir
requests are fine for the first few thousand, but nearly all of them
have one or more duplicates after that.  There is no justification for
those duplicates - all the original requests are getting replies.

It's possible that the server is taking longer to respond to
READDIRPLUS than to GETATTR.  That makes sense, because the
READDIRPLUS reads inodes from disk, then GETATTR just reads them from
memory.  Let's take a look...

Yup!  In the traces, GETATTR responds consistently in 0.0002 seconds
(close to ping time, clearly no disk access), whereas READDIRPLUS
takes some 0.2 seconds to respond.

I see that the RTT estimation _is_ adapting quickly to this: the first
READDIRPLUS in a sequence has several duplicates; subsequent ones don't.

Suggestion:

  - With RTT estimation, "not responding" should require a certain
    amount of absolute time to pass, e.g. 5 seconds, not just a fixed
    number of packets.  Without this, "soft" is broken because the
    time difference between a response for cached data and a response
    from the disk is a factor of several hundred.

Note that I'm looking as "ls -R" now because it's easy to repeat, but
the EIO problem occurs with file reading and writing too.

-- Jamie


p.s Another quirk is I see the server sending more than one duplicate
    reply to each duplicate READDIRPLUS request...  Well, that's a
    separate problem I think :)

Re: NFS client errors with 2.5.74?

[Trond Myklebust]

>>>>> " " == Jamie Lokier <jamie@shareable.org> writes:

     > all the original requests are getting replies.

OK. That *is* definitely a bug... Let me ponder a bit. I'm working
through that logic right now...

Cheers,
  Trond

Re: NFS client errors with 2.5.74?

[Trond Myklebust]

[-- Attachment #1: message body text --]
[-- Type: text/plain, Size: 583 bytes --]


OK... I have two patches for you... (I've attached them as plaintext
MIME thingmajigs)...

The first one should fix the problem of the kernel missing replies
while we are busy trying to resend a request.

The second, solves a problem of resource starvation. The fact that we
can currently just submit arbitrary numbers of asynchronous requests
means that we can exhaust resources to the point where the socket
starts dropping replies.
This patch limits the number of outstanding asynchronous requests to
16 per socket (the maximum number of xprt/transport slots).

Cheers,
  Trond


[-- Attachment #2: patch 1/2 --]
[-- Type: text/plain, Size: 6341 bytes --]

diff -u --recursive --new-file linux-2.5.74/include/linux/sunrpc/xprt.h linux-2.5.74-13-resends/include/linux/sunrpc/xprt.h
--- linux-2.5.74/include/linux/sunrpc/xprt.h	2003-07-10 22:52:35.000000000 +0200
+++ linux-2.5.74-13-resends/include/linux/sunrpc/xprt.h	2003-07-10 22:53:45.000000000 +0200
@@ -111,7 +111,7 @@
 
 	unsigned long		rq_xtime;	/* when transmitted */
 	int			rq_ntimeo;
-	int			rq_nresend;
+	int			rq_ntrans;
 };
 #define rq_svec			rq_snd_buf.head
 #define rq_slen			rq_snd_buf.len
diff -u --recursive --new-file linux-2.5.74/net/sunrpc/clnt.c linux-2.5.74-13-resends/net/sunrpc/clnt.c
--- linux-2.5.74/net/sunrpc/clnt.c	2003-06-12 04:22:40.000000000 +0200
+++ linux-2.5.74-13-resends/net/sunrpc/clnt.c	2003-07-10 21:43:21.000000000 +0200
@@ -658,7 +658,7 @@
 	if (task->tk_status < 0)
 		return;
 	task->tk_status = xprt_prepare_transmit(task);
-	if (task->tk_status < 0)
+	if (task->tk_status != 0)
 		return;
 	/* Encode here so that rpcsec_gss can use correct sequence number. */
 	if (!task->tk_rqstp->rq_bytes_sent)
@@ -684,7 +684,7 @@
 	struct rpc_rqst	*req = task->tk_rqstp;
 	int		status;
 
-	if (req->rq_received != 0)
+	if (req->rq_received != 0 && !req->rq_bytes_sent)
 		task->tk_status = req->rq_received;
 
 	dprintk("RPC: %4d call_status (status %d)\n", 
@@ -743,7 +743,7 @@
 
 	dprintk("RPC: %4d call_timeout (major)\n", task->tk_pid);
 	if (clnt->cl_softrtry) {
-		if (clnt->cl_chatty && !task->tk_exit)
+		if (clnt->cl_chatty)
 			printk(KERN_NOTICE "%s: server %s not responding, timed out\n",
 				clnt->cl_protname, clnt->cl_server);
 		rpc_exit(task, -EIO);
@@ -786,8 +786,9 @@
 
 	if (task->tk_status < 12) {
 		if (!clnt->cl_softrtry) {
-			task->tk_action = call_transmit;
+			task->tk_action = call_bind;
 			clnt->cl_stats->rpcretrans++;
+			req->rq_received = 0;
 		} else {
 			printk(KERN_WARNING "%s: too small RPC reply size (%d bytes)\n",
 				clnt->cl_protname, task->tk_status);
@@ -797,8 +798,10 @@
 	}
 
 	/* Verify the RPC header */
-	if (!(p = call_verify(task)))
+	if (!(p = call_verify(task))) {
+		req->rq_received = 0;
 		return;
+	}
 
 	/*
 	 * The following is an NFS-specific hack to cater for setuid
diff -u --recursive --new-file linux-2.5.74/net/sunrpc/xprt.c linux-2.5.74-13-resends/net/sunrpc/xprt.c
--- linux-2.5.74/net/sunrpc/xprt.c	2003-06-10 06:26:58.000000000 +0200
+++ linux-2.5.74-13-resends/net/sunrpc/xprt.c	2003-07-10 22:53:36.000000000 +0200
@@ -140,15 +140,21 @@
 static int
 __xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
 {
+	struct rpc_rqst *req = task->tk_rqstp;
 	if (!xprt->snd_task) {
-		if (xprt->nocong || __xprt_get_cong(xprt, task))
+		if (xprt->nocong || __xprt_get_cong(xprt, task)) {
 			xprt->snd_task = task;
+			if (req) {
+				req->rq_bytes_sent = 0;
+				req->rq_ntrans++;
+			}
+		}
 	}
 	if (xprt->snd_task != task) {
 		dprintk("RPC: %4d TCP write queue full\n", task->tk_pid);
 		task->tk_timeout = 0;
 		task->tk_status = -EAGAIN;
-		if (task->tk_rqstp && task->tk_rqstp->rq_nresend)
+		if (req && req->rq_ntrans)
 			rpc_sleep_on(&xprt->resend, task, NULL, NULL);
 		else
 			rpc_sleep_on(&xprt->sending, task, NULL, NULL);
@@ -183,8 +189,14 @@
 		if (!task)
 			return;
 	}
-	if (xprt->nocong || __xprt_get_cong(xprt, task))
+	if (xprt->nocong || __xprt_get_cong(xprt, task)) {
+		struct rpc_rqst *req = task->tk_rqstp;
 		xprt->snd_task = task;
+		if (req) {
+			req->rq_bytes_sent = 0;
+			req->rq_ntrans++;
+		}
+	}
 }
 
 /*
@@ -424,6 +436,9 @@
 	if (xprt_connected(xprt))
 		goto out_write;
 
+	if (task->tk_rqstp)
+		task->tk_rqstp->rq_bytes_sent = 0;
+
 	/*
 	 * We're here because the xprt was marked disconnected.
 	 * Start by resetting any existing state.
@@ -567,7 +582,7 @@
 	if (!xprt->nocong) {
 		xprt_adjust_cwnd(xprt, copied);
 		__xprt_put_cong(xprt, req);
-	       	if (!req->rq_nresend) {
+	       	if (req->rq_ntrans == 1) {
 			unsigned timer =
 				task->tk_msg.rpc_proc->p_timer;
 			if (timer)
@@ -1075,8 +1090,8 @@
 		}
 		rpc_inc_timeo(&task->tk_client->cl_rtt);
 		xprt_adjust_cwnd(req->rq_xprt, -ETIMEDOUT);
+		__xprt_put_cong(xprt, req);
 	}
-	req->rq_nresend++;
 
 	dprintk("RPC: %4d xprt_timer (%s request)\n",
 		task->tk_pid, req ? "pending" : "backlogged");
@@ -1109,6 +1124,11 @@
 		rpc_remove_wait_queue(task);
 
 	spin_lock_bh(&xprt->sock_lock);
+	if (req->rq_received) {
+		err = req->rq_received;
+		goto out_unlock;
+	}
+
 	if (!__xprt_lock_write(xprt, task)) {
 		err = -EAGAIN;
 		goto out_unlock;
@@ -1119,10 +1139,8 @@
 		goto out_unlock;
 	}
 
-	if (list_empty(&req->rq_list)) {
+	if (list_empty(&req->rq_list))
 		list_add_tail(&req->rq_list, &xprt->recv);
-		req->rq_received = 0;
-	}
 out_unlock:
 	spin_unlock_bh(&xprt->sock_lock);
 	return err;
@@ -1136,7 +1154,6 @@
 	struct rpc_xprt	*xprt = req->rq_xprt;
 	int status, retry = 0;
 
-
 	dprintk("RPC: %4d xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
 
 	/* set up everything as needed. */
@@ -1161,8 +1178,10 @@
 		if (xprt->stream) {
 			req->rq_bytes_sent += status;
 
-			if (req->rq_bytes_sent >= req->rq_slen)
+			if (req->rq_bytes_sent >= req->rq_slen) {
+				req->rq_bytes_sent = 0;
 				goto out_receive;
+			}
 		} else {
 			if (status >= req->rq_slen)
 				goto out_receive;
@@ -1183,9 +1202,6 @@
 	 *	 hence there is no danger of the waking up task being put on
 	 *	 schedq, and being picked up by a parallel run of rpciod().
 	 */
-	if (req->rq_received)
-		goto out_release;
-
 	task->tk_status = status;
 
 	switch (status) {
@@ -1215,13 +1231,12 @@
 		if (xprt->stream)
 			xprt_disconnect(xprt);
 	}
- out_release:
 	xprt_release_write(xprt, task);
-	req->rq_bytes_sent = 0;
 	return;
  out_receive:
 	dprintk("RPC: %4d xmit complete\n", task->tk_pid);
 	/* Set the task's receive timeout value */
+	spin_lock_bh(&xprt->sock_lock);
 	if (!xprt->nocong) {
 		task->tk_timeout = rpc_calc_rto(&clnt->cl_rtt,
 				task->tk_msg.rpc_proc->p_timer);
@@ -1230,7 +1245,6 @@
 			task->tk_timeout = req->rq_timeout.to_maxval;
 	} else
 		task->tk_timeout = req->rq_timeout.to_current;
-	spin_lock_bh(&xprt->sock_lock);
 	/* Don't race with disconnect */
 	if (!xprt_connected(xprt))
 		task->tk_status = -ENOTCONN;
@@ -1238,7 +1252,6 @@
 		rpc_sleep_on(&xprt->pending, task, NULL, xprt_timer);
 	__xprt_release_write(xprt, task);
 	spin_unlock_bh(&xprt->sock_lock);
-	req->rq_bytes_sent = 0;
 }
 
 /*

[-- Attachment #3: patch 2/2 --]
[-- Type: text/plain, Size: 6592 bytes --]

diff -u --recursive --new-file linux-2.5.74-14-soft/include/linux/sunrpc/clnt.h linux-2.5.74-15-mem/include/linux/sunrpc/clnt.h
--- linux-2.5.74-14-soft/include/linux/sunrpc/clnt.h	2003-02-13 13:57:46.000000000 +0100
+++ linux-2.5.74-15-mem/include/linux/sunrpc/clnt.h	2003-07-11 00:48:39.000000000 +0200
@@ -35,6 +35,7 @@
  */
 struct rpc_clnt {
 	atomic_t		cl_users;	/* number of references */
+	atomic_t		cl_active;	/* number of active calls */
 	struct rpc_xprt *	cl_xprt;	/* transport */
 	struct rpc_procinfo *	cl_procinfo;	/* procedure info */
 	u32			cl_maxproc;	/* max procedure number */
@@ -57,6 +58,7 @@
 
 	struct rpc_portmap	cl_pmap;	/* port mapping */
 	struct rpc_wait_queue	cl_bindwait;	/* waiting on getport() */
+	wait_queue_head_t	cl_waitq;	/* wait queue */
 
 	int			cl_nodelen;	/* nodename length */
 	char 			cl_nodename[UNX_MAXNODENAME];
@@ -124,6 +126,15 @@
 void		rpc_clnt_sigmask(struct rpc_clnt *clnt, sigset_t *oldset);
 void		rpc_clnt_sigunmask(struct rpc_clnt *clnt, sigset_t *oldset);
 void		rpc_setbufsize(struct rpc_clnt *, unsigned int, unsigned int);
+int		rpc_congestion_wait(struct rpc_clnt *);
+
+static inline void rpc_mark_active(struct rpc_task *task)
+{
+	struct rpc_clnt *clnt = task->tk_client;
+	task->tk_active = 1;
+	if (clnt)
+		atomic_inc(&clnt->cl_active);
+}
 
 static __inline__
 int rpc_call(struct rpc_clnt *clnt, u32 proc, void *argp, void *resp, int flags)
diff -u --recursive --new-file linux-2.5.74-14-soft/net/sunrpc/clnt.c linux-2.5.74-15-mem/net/sunrpc/clnt.c
--- linux-2.5.74-14-soft/net/sunrpc/clnt.c	2003-07-10 21:46:14.000000000 +0200
+++ linux-2.5.74-15-mem/net/sunrpc/clnt.c	2003-07-11 00:49:31.000000000 +0200
@@ -127,6 +127,7 @@
 	clnt->cl_prot     = xprt->prot;
 	clnt->cl_stats    = program->stats;
 	INIT_RPC_WAITQ(&clnt->cl_bindwait, "bindwait");
+	init_waitqueue_head(&clnt->cl_waitq);
 
 	if (!clnt->cl_port)
 		clnt->cl_autobind = 1;
@@ -389,6 +390,37 @@
 }
 
 /*
+ * Throttle the number of active RPC requests
+ */
+int
+rpc_congestion_wait(struct rpc_clnt *clnt)
+{
+	int ret = 0;
+	DECLARE_WAITQUEUE(wait, current);
+
+	if (atomic_read(&clnt->cl_active) < RPC_MAXCONG)
+		goto out;
+	add_wait_queue(&clnt->cl_waitq, &wait);
+	for (;;) {
+		if (clnt->cl_intr)
+			set_current_state(TASK_INTERRUPTIBLE);
+		else
+			set_current_state(TASK_UNINTERRUPTIBLE);
+		if (atomic_read(&clnt->cl_active) < RPC_MAXCONG)
+			break;
+		if (clnt->cl_intr && signal_pending(current)) {
+			ret = -ERESTARTSYS;
+			break;
+		}
+		io_schedule();
+	}
+	current->state = TASK_RUNNING;
+	remove_wait_queue(&clnt->cl_waitq, &wait);
+out:
+	return ret;
+}
+
+/*
  * Restart an (async) RPC call. Usually called from within the
  * exit handler.
  */
diff -u --recursive --new-file linux-2.5.74-14-soft/net/sunrpc/sched.c linux-2.5.74-15-mem/net/sunrpc/sched.c
--- linux-2.5.74-14-soft/net/sunrpc/sched.c	2003-06-20 22:16:26.000000000 +0200
+++ linux-2.5.74-15-mem/net/sunrpc/sched.c	2003-07-11 00:47:23.000000000 +0200
@@ -257,13 +257,11 @@
 				return;
 			}
 			rpc_clear_sleeping(task);
-			if (waitqueue_active(&rpciod_idle))
-				wake_up(&rpciod_idle);
+			wake_up(&rpciod_idle);
 		}
 	} else {
 		rpc_clear_sleeping(task);
-		if (waitqueue_active(&task->tk_wait))
-			wake_up(&task->tk_wait);
+		wake_up(&task->tk_wait);
 	}
 }
 
@@ -276,7 +274,7 @@
 	/* Don't run a child twice! */
 	if (RPC_IS_ACTIVATED(task))
 		return;
-	task->tk_active = 1;
+	rpc_mark_active(task);
 	rpc_set_sleeping(task);
 	rpc_make_runnable(task);
 }
@@ -289,8 +287,7 @@
 {
 	if(rpciod_pid==0)
 		printk(KERN_ERR "rpciod: wot no daemon?\n");
-	if (waitqueue_active(&rpciod_idle))
-		wake_up(&rpciod_idle);
+	wake_up(&rpciod_idle);
 }
 
 /*
@@ -315,7 +312,7 @@
 
 	/* Mark the task as being activated if so needed */
 	if (!RPC_IS_ACTIVATED(task)) {
-		task->tk_active = 1;
+		rpc_mark_active(task);
 		rpc_set_sleeping(task);
 	}
 
@@ -488,7 +485,8 @@
 static int
 __rpc_execute(struct rpc_task *task)
 {
-	int		status = 0;
+	int interruptible = task->tk_client->cl_intr;
+	int status = 0;
 
 	dprintk("RPC: %4d rpc_execute flgs %x\n",
 				task->tk_pid, task->tk_flags);
@@ -547,14 +545,24 @@
 		}
 		spin_unlock_bh(&rpc_queue_lock);
 
-		while (RPC_IS_SLEEPING(task)) {
+		if (RPC_IS_SLEEPING(task)) {
+			DEFINE_WAIT(wait);
+
 			/* sync task: sleep here */
 			dprintk("RPC: %4d sync task going to sleep\n",
 							task->tk_pid);
 			if (current->pid == rpciod_pid)
 				printk(KERN_ERR "RPC: rpciod waiting on sync task!\n");
 
-			__wait_event(task->tk_wait, !RPC_IS_SLEEPING(task));
+			prepare_to_wait(&task->tk_wait, &wait,
+					interruptible ? TASK_INTERRUPTIBLE :
+							TASK_UNINTERRUPTIBLE);
+			if (likely(RPC_IS_SLEEPING(task))) {
+				if (likely(!(signalled() && interruptible)))
+					io_schedule();
+			}
+			finish_wait(&task->tk_wait, &wait);
+
 			dprintk("RPC: %4d sync task resuming\n", task->tk_pid);
 
 			/*
@@ -563,7 +571,7 @@
 			 * clean up after sleeping on some queue, we don't
 			 * break the loop here, but go around once more.
 			 */
-			if (task->tk_client->cl_intr && signalled()) {
+			if (unlikely(signalled() && interruptible)) {
 				dprintk("RPC: %4d got signal\n", task->tk_pid);
 				task->tk_flags |= RPC_TASK_KILLED;
 				rpc_exit(task, -ERESTARTSYS);
@@ -620,7 +628,12 @@
 		goto out_err;
 	}
 
-	task->tk_active = 1;
+	if (task->tk_client) {
+		status = rpc_congestion_wait(task->tk_client);
+		if (status < 0)
+			goto out_release;
+	}
+	rpc_mark_active(task);
 	rpc_set_running(task);
 	return __rpc_execute(task);
  out_release:
@@ -818,8 +831,6 @@
 	/* Remove from any wait queue we're still on */
 	__rpc_remove_wait_queue(task);
 
-	task->tk_active = 0;
-
 	spin_unlock_bh(&rpc_queue_lock);
 
 	/* Synchronously delete any running timer */
@@ -832,6 +843,10 @@
 		rpcauth_unbindcred(task);
 	rpc_free(task);
 	if (task->tk_client) {
+		if (task->tk_active) {
+			atomic_dec(&task->tk_client->cl_active);
+			wake_up(&task->tk_client->cl_waitq);
+		}
 		rpc_release_client(task->tk_client);
 		task->tk_client = NULL;
 	}
@@ -979,8 +994,20 @@
 		}
 
 		if (!rpciod_task_pending()) {
+			DEFINE_WAIT(wait);
+
 			dprintk("RPC: rpciod back to sleep\n");
-			wait_event_interruptible(rpciod_idle, rpciod_task_pending());
+
+			prepare_to_wait(&rpciod_idle, &wait, TASK_INTERRUPTIBLE);
+			spin_lock_bh(&rpc_queue_lock);
+			if (likely(!rpciod_task_pending())) {
+				spin_unlock_bh(&rpc_queue_lock);
+				if (likely(!signalled()))
+					schedule();
+			} else
+				spin_unlock_bh(&rpc_queue_lock);
+			finish_wait(&rpciod_idle, &wait);
+
 			dprintk("RPC: switch to rpciod\n");
 			rounds = 0;
 		}

Re: NFS client errors with 2.5.74?

[Jamie Lokier]

Trond Myklebust wrote:
> The first one should fix the problem of the kernel missing replies
> while we are busy trying to resend a request.

This by itself doesn't fix the problem of too-fast timeout errors on
soft mounts (e.g. returning EIO within <0.1s).

I am still seeing the fs get into a state where each time a large file
is written, it reports EIO (but writes successfully anyway).  And "ls
-R" still shows EIO errors also.

> The second, solves a problem of resource starvation. The fact that we
> can currently just submit arbitrary numbers of asynchronous requests
> means that we can exhaust resources to the point where the socket
> starts dropping replies.
> This patch limits the number of outstanding asynchronous requests to
> 16 per socket (the maximum number of xprt/transport slots).

I haven't tried this yet.  It doesn't apply to 2.5.74 due to the calls
to io_schedule().

- Jamie

Re: NFS client errors with 2.5.74?

[Jamie Lokier]

Jamie Lokier wrote:
> I haven't tried this yet.  It doesn't apply to 2.5.74 due to the calls
> to io_schedule().

I've tried both patches together now, on 2.5.75.  Still seeing fast
(<0.1s) timeouts with "soft".  Using "hard" seems fairly reliable, but
that was the same without the patches.

-- Jamie

Re: NFS client errors with 2.5.74?

[Frank Cusack]

On Thu, Jul 10, 2003 at 12:15:24PM +0200, Trond Myklebust wrote:
> >>>>> " " == Jamie Lokier <jamie@shareable.org> writes:
>      > - Every so often, the client's kernel log gets:
>      >       kernel: nfs: server 192.168.1.1 not responding, timed out
> 
> Sigh... I hate soft mounts...  Have I said that before? 8-)

Is "timed out" the key that this is a soft mount?  Trond, I would suggest
that whenever you log this, you also log a message "... do not report
a bug, use a hard mount" or some such. :-)

/fc

NFS client errors with 2.5.74?

[Michael Frank]

I chewed on that a while ago and was advised not to use "soft" mounts.

My 2.4<>2.4 setup worked with "soft" for ages, but it broke when
running 2.5.6x/7x on the server.

If you are using soft mounts, use "hard,intr" instead. 

Regards
Michael

-- 
Powered by linux-2.5.74-mm3. Compiled with gcc-2.95-3 - mature and rock solid

My current linux related activities:
- 2.5 yenta_socket testing
- Test development and testing of swsusp for 2.4/2.5 and ACPI S3 of 2.5 kernel 
- Everyday usage of 2.5 kernel

More info on 2.5 kernel: http://www.codemonkey.org.uk/post-halloween-2.5.txt
More info on swsusp: http://sourceforge.net/projects/swsusp/

Re: NFS client errors with 2.5.74?

[Trond Myklebust]

>>>>> " " == Jamie Lokier <jamie@shareable.org> writes:
     > - Every so often, the client's kernel log gets:
     >       kernel: nfs: server 192.168.1.1 not responding, timed out

Sigh... I hate soft mounts...  Have I said that before? 8-)

     > Any idea about this?  Is it a known problem?

I can never guarantee you perfect service with soft mounts (a 5 second
network patition/server congestion is all it takes) but I do have a
patch that just went into 2.4.22 that backs out some of the
Van Jacobson exponential backoff changes. This helps stabilize things
a lot.

I haven't yet had time to port that patch to 2.5.x, but the code
should be pretty much identical, so if you want to give it a go, then
here it is...

Cheers,
  Trond

diff -u --recursive --new-file linux-2.4.21-20-rdplus/net/sunrpc/clnt.c linux-2.4.21-21-soft/net/sunrpc/clnt.c
--- linux-2.4.21-20-rdplus/net/sunrpc/clnt.c	2003-06-15 14:49:35.000000000 -0700
+++ linux-2.4.21-21-soft/net/sunrpc/clnt.c	2003-06-17 10:38:56.000000000 -0700
@@ -709,14 +709,14 @@
 
 	dprintk("RPC: %4d call_timeout (major)\n", task->tk_pid);
 	if (clnt->cl_softrtry) {
-		if (clnt->cl_chatty && !task->tk_exit)
+		if (clnt->cl_chatty)
 			printk(KERN_NOTICE "%s: server %s not responding, timed out\n",
 				clnt->cl_protname, clnt->cl_server);
 		rpc_exit(task, -EIO);
 		return;
 	}
 
-	if (clnt->cl_chatty && !(task->tk_flags & RPC_CALL_MAJORSEEN) && rpc_ntimeo(&clnt->cl_rtt) > 7) {
+	if (clnt->cl_chatty && !(task->tk_flags & RPC_CALL_MAJORSEEN)) {
 		task->tk_flags |= RPC_CALL_MAJORSEEN;
 		printk(KERN_NOTICE "%s: server %s not responding, still trying\n",
 			clnt->cl_protname, clnt->cl_server);
diff -u --recursive --new-file linux-2.4.21-20-rdplus/net/sunrpc/xprt.c linux-2.4.21-21-soft/net/sunrpc/xprt.c
--- linux-2.4.21-20-rdplus/net/sunrpc/xprt.c	2003-06-15 15:14:14.000000000 -0700
+++ linux-2.4.21-21-soft/net/sunrpc/xprt.c	2003-06-17 09:48:18.000000000 -0700
@@ -1046,21 +1046,6 @@
 }
 
 /*
- * Exponential backoff for UDP retries
- */
-static inline int
-xprt_expbackoff(struct rpc_task *task, struct rpc_rqst *req)
-{
-	int backoff;
-
-	req->rq_ntimeo++;
-	backoff = min(rpc_ntimeo(&task->tk_client->cl_rtt), XPRT_MAX_BACKOFF);
-	if (req->rq_ntimeo < (1 << backoff))
-		return 1;
-	return 0;
-}
-
-/*
  * RPC receive timeout handler.
  */
 static void
@@ -1073,14 +1058,7 @@
 	if (req->rq_received)
 		goto out;
 
-	if (!xprt->nocong) {
-		if (xprt_expbackoff(task, req)) {
-			rpc_add_timer(task, xprt_timer);
-			goto out_unlock;
-		}
-		rpc_inc_timeo(&task->tk_client->cl_rtt);
-		xprt_adjust_cwnd(req->rq_xprt, -ETIMEDOUT);
-	}
+	xprt_adjust_cwnd(req->rq_xprt, -ETIMEDOUT);
 	req->rq_nresend++;
 
 	dprintk("RPC: %4d xprt_timer (%s request)\n",
@@ -1090,7 +1068,6 @@
 out:
 	task->tk_timeout = 0;
 	rpc_wake_up_task(task);
-out_unlock:
 	spin_unlock(&xprt->sock_lock);
 }
 
@@ -1228,16 +1205,17 @@
 	return;
  out_receive:
 	dprintk("RPC: %4d xmit complete\n", task->tk_pid);
+	spin_lock_bh(&xprt->sock_lock);
 	/* Set the task's receive timeout value */
 	if (!xprt->nocong) {
 		task->tk_timeout = rpc_calc_rto(&clnt->cl_rtt,
 				rpcproc_timer(clnt, task->tk_msg.rpc_proc));
-		req->rq_ntimeo = 0;
+		task->tk_timeout <<= clnt->cl_timeout.to_retries
+			- req->rq_timeout.to_retries;
 		if (task->tk_timeout > req->rq_timeout.to_maxval)
 			task->tk_timeout = req->rq_timeout.to_maxval;
 	} else
 		task->tk_timeout = req->rq_timeout.to_current;
-	spin_lock_bh(&xprt->sock_lock);
 	/* Don't race with disconnect */
 	if (!xprt_connected(xprt))
 		task->tk_status = -ENOTCONN;

Re: NFS client errors with 2.5.74?

[Felipe Alfaro Solana]

On Thu, 2003-07-10 at 07:41, Jamie Lokier wrote:
> I'm seeing quite a lot of NFS client errors with 2.5.74, connected to
> a server running 2.4.20-18.9 (Red Hat 9's current kernel).
> 
> All of the errors that I've observed the form of a write() or close()
> returning EIO.  rsync seeems to have a particularly tough time -
> could the unusual size of blocks which rsync writes be relevant?
> 
> There are some read errors too, as Mozilla failed to find my profile
> claiming it couldn't read the file (when I restarted Mozilla, it found
> it the second time), and Gnome Terminal was unable to read its
> preferences file, but I didn't catch any specific read() errors.
> 
> I tried this command to see if the is a protocol error while running
> Ethereal:
> 
> [jamie@dual jamie]$ cp .mirMail.bjl1/INBOX .mirMail.bjl1/JBOX
> cp: closing `.mirMail.bjl1/JBOX': Input/output error

Any chance you are using "hard" NFS mounts?

Re: NFS client errors with 2.5.74?

[Jamie Lokier]

Some more information:

The kernel messages "kernel: nfs: server 192.168.1.1 not responding,
timed out" do have some relationship with the EIO errors after all.

When I "ls" a directory for the first time (i.e. it's not in cache), I
get an EIO _every time_.  It's the getdents64() call which returns EIO.

The second and subsequent times I list that directory, the listing is
fine.  However if I pick another directory which isn't in cache yet,
getdents64() returns EIO.

A packet trace shows something interesting: duplicate requests.

In this case, I see four (4) READDIRPLUS requests with identical XIDs.
Ethereal says that all four are sent in 0.04 seconds.

Then I see four replies, of course with identical XIDs too.  The
replies all have status OK.  But four duplicate requests is mighty
suspicious.

-- Jamie

NFS client errors with 2.5.74?

[Jamie Lokier]

I'm seeing quite a lot of NFS client errors with 2.5.74, connected to
a server running 2.4.20-18.9 (Red Hat 9's current kernel).

All of the errors that I've observed the form of a write() or close()
returning EIO.  rsync seeems to have a particularly tough time -
could the unusual size of blocks which rsync writes be relevant?

There are some read errors too, as Mozilla failed to find my profile
claiming it couldn't read the file (when I restarted Mozilla, it found
it the second time), and Gnome Terminal was unable to read its
preferences file, but I didn't catch any specific read() errors.

I tried this command to see if the is a protocol error while running
Ethereal:

[jamie@dual jamie]$ cp .mirMail.bjl1/INBOX .mirMail.bjl1/JBOX
cp: closing `.mirMail.bjl1/JBOX': Input/output error

Ethereal shows a long series of NFS WRITEs followed by a single COMMIT
(as expected), and nothing after that.  All of those replies had
status 0, OK - including the reply to the final COMMIT.

Using "md5sum" I checked on both the client and server, and the
contents of "JBOX" have been written correctly despite the
"Input/output error" from "cp".

When I looked at the packets from rsync commands that I saw getting
EIO from write(), I saw that all requests except LOOKUP returned with
status 0 as well, and the LOOKUPs that failed were simply checking
whether a ".nfs..." name exists before renaming another file to that
name.

So as far as I can tell, there is no problem with the packets being
sent and received.  There is, however, a big problem with error
reporting on the client side.

A few extra notes:

  - Running NFS v3.
  - Kernel is vanilla 2.5.74, dual Athlon 1800MP, 768MB RAM
  - Chipset: AMD-760MP/AMD-768.  Board: Asus A7M266-D.

  - I _think_ I noticed this problem once when running 2.4.20-18.9 on
    the client, but generally it is not a problem.  I have been
    mounting my home directory over NFS for weeks with 2.4.20-18.9 as
    client, so I would have noticed networking or server problems.

  - Every so often, the client's kernel log gets:
      kernel: nfs: server 192.168.1.1 not responding, timed out
    I haven't caught one of those with Ethereal to find out what's
    going on the wire.  There are no other regular kernel messages.

    Note!  These are all logged at different times to the EIOs,
    differet as in minutes away.  The EIOs, btw, are reported
    immediately; there is no pause waiting for a response from the
    server.

Any idea about this?  Is it a known problem?

Cheers,
-- Jamie