[PATCH net 0/7] rxrpc, afs: Fix probing issues

[PATCH net 0/7] rxrpc, afs: Fix probing issues

[David Howells]

Here are some fixes for rxrpc and afs to fix issues in the RTT measuring in
rxrpc and thence the Volume Location server probing in afs:

 (1) Move the serial number of a received ACK into a local variable to
     simplify the next patch.

 (2) Fix the loss of RTT samples due to extra interposed ACKs causing
     baseline information to be discarded too early.  This is a particular
     problem for afs when it sends a single very short call to probe a
     server it hasn't talked to recently.

 (3) Fix rxrpc_kernel_get_srtt() to indicate whether it actually has seen
     any valid samples or not.

 (4) Remove a field that's set/woken, but never read/waited on.

 (5) Expose the RTT and other probe information through procfs to make
     debugging of this stuff easier.

 (6) Fix VL rotation in afs to only use summary information from VL probing
     and not the probe running state (which gets clobbered when next a
     probe is issued).

 (7) Fix VL rotation to actually return the error aggregated from the probe
     errors.

The patches are tagged here:

	git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
	rxrpc-fixes-20200820

and can also be found on the following branch:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=rxrpc-fixes

David
---
David Howells (7):
      rxrpc: Keep the ACK serial in a var in rxrpc_input_ack()
      rxrpc: Fix loss of RTT samples due to interposed ACK
      rxrpc: Make rxrpc_kernel_get_srtt() indicate validity
      afs: Remove afs_vlserver->probe.have_result
      afs: Expose information from afs_vlserver through /proc for debugging
      afs: Don't use VL probe running state to make decisions outside probe code
      afs: Fix error handling in VL server rotation


 fs/afs/fs_probe.c            |   4 +-
 fs/afs/internal.h            |  14 +++--
 fs/afs/proc.c                |   5 ++
 fs/afs/vl_list.c             |   1 +
 fs/afs/vl_probe.c            |  82 ++++++++++++++++-----------
 fs/afs/vl_rotate.c           |   7 ++-
 include/net/af_rxrpc.h       |   2 +-
 include/trace/events/rxrpc.h |  27 +++++++--
 net/rxrpc/ar-internal.h      |  13 +++--
 net/rxrpc/call_object.c      |   1 +
 net/rxrpc/input.c            | 104 ++++++++++++++++++++---------------
 net/rxrpc/output.c           |  82 ++++++++++++++++++++-------
 net/rxrpc/peer_object.c      |  16 +++++-
 net/rxrpc/rtt.c              |   3 +-
 14 files changed, 241 insertions(+), 120 deletions(-)

[PATCH net 1/7] rxrpc: Keep the ACK serial in a var in rxrpc_input_ack()

[David Howells]

Keep the ACK serial number in a variable in rxrpc_input_ack() as it's used
frequently.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 net/rxrpc/input.c |   21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 767579328a06..a7699e56eac8 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -843,7 +843,7 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 		struct rxrpc_ackinfo info;
 		u8 acks[RXRPC_MAXACKS];
 	} buf;
-	rxrpc_serial_t acked_serial;
+	rxrpc_serial_t ack_serial, acked_serial;
 	rxrpc_seq_t first_soft_ack, hard_ack, prev_pkt;
 	int nr_acks, offset, ioffset;
 
@@ -856,6 +856,7 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 	}
 	offset += sizeof(buf.ack);
 
+	ack_serial = sp->hdr.serial;
 	acked_serial = ntohl(buf.ack.serial);
 	first_soft_ack = ntohl(buf.ack.firstPacket);
 	prev_pkt = ntohl(buf.ack.previousPacket);
@@ -864,31 +865,31 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 	summary.ack_reason = (buf.ack.reason < RXRPC_ACK__INVALID ?
 			      buf.ack.reason : RXRPC_ACK__INVALID);
 
-	trace_rxrpc_rx_ack(call, sp->hdr.serial, acked_serial,
+	trace_rxrpc_rx_ack(call, ack_serial, acked_serial,
 			   first_soft_ack, prev_pkt,
 			   summary.ack_reason, nr_acks);
 
 	if (buf.ack.reason == RXRPC_ACK_PING_RESPONSE)
 		rxrpc_input_ping_response(call, skb->tstamp, acked_serial,
-					  sp->hdr.serial);
+					  ack_serial);
 	if (buf.ack.reason == RXRPC_ACK_REQUESTED)
 		rxrpc_input_requested_ack(call, skb->tstamp, acked_serial,
-					  sp->hdr.serial);
+					  ack_serial);
 
 	if (buf.ack.reason == RXRPC_ACK_PING) {
-		_proto("Rx ACK %%%u PING Request", sp->hdr.serial);
+		_proto("Rx ACK %%%u PING Request", ack_serial);
 		rxrpc_propose_ACK(call, RXRPC_ACK_PING_RESPONSE,
-				  sp->hdr.serial, true, true,
+				  ack_serial, true, true,
 				  rxrpc_propose_ack_respond_to_ping);
 	} else if (sp->hdr.flags & RXRPC_REQUEST_ACK) {
 		rxrpc_propose_ACK(call, RXRPC_ACK_REQUESTED,
-				  sp->hdr.serial, true, true,
+				  ack_serial, true, true,
 				  rxrpc_propose_ack_respond_to_ack);
 	}
 
 	/* Discard any out-of-order or duplicate ACKs (outside lock). */
 	if (!rxrpc_is_ack_valid(call, first_soft_ack, prev_pkt)) {
-		trace_rxrpc_rx_discard_ack(call->debug_id, sp->hdr.serial,
+		trace_rxrpc_rx_discard_ack(call->debug_id, ack_serial,
 					   first_soft_ack, call->ackr_first_seq,
 					   prev_pkt, call->ackr_prev_seq);
 		return;
@@ -904,7 +905,7 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 
 	/* Discard any out-of-order or duplicate ACKs (inside lock). */
 	if (!rxrpc_is_ack_valid(call, first_soft_ack, prev_pkt)) {
-		trace_rxrpc_rx_discard_ack(call->debug_id, sp->hdr.serial,
+		trace_rxrpc_rx_discard_ack(call->debug_id, ack_serial,
 					   first_soft_ack, call->ackr_first_seq,
 					   prev_pkt, call->ackr_prev_seq);
 		goto out;
@@ -964,7 +965,7 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 	    RXRPC_TX_ANNO_LAST &&
 	    summary.nr_acks == call->tx_top - hard_ack &&
 	    rxrpc_is_client_call(call))
-		rxrpc_propose_ACK(call, RXRPC_ACK_PING, sp->hdr.serial,
+		rxrpc_propose_ACK(call, RXRPC_ACK_PING, ack_serial,
 				  false, true,
 				  rxrpc_propose_ack_ping_for_lost_reply);
 

[PATCH net 2/7] rxrpc: Fix loss of RTT samples due to interposed ACK

[David Howells]

The Rx protocol has a mechanism to help generate RTT samples that works by
a client transmitting a REQUESTED-type ACK when it receives a DATA packet
that has the REQUEST_ACK flag set.

The peer, however, may interpose other ACKs before transmitting the
REQUESTED-ACK, as can be seen in the following trace excerpt:

 rxrpc_tx_data: c=00000044 DATA d0b5ece8:00000001 00000001 q=00000001 fl=07
 rxrpc_rx_ack: c=00000044 00000001 PNG r=00000000 f=00000002 p=00000000 n=0
 rxrpc_rx_ack: c=00000044 00000002 REQ r=00000001 f=00000002 p=00000001 n=0
 ...

DATA packet 1 (q=xx) has REQUEST_ACK set (bit 1 of fl=xx).  The incoming
ping (labelled PNG) hard-acks the request DATA packet (f=xx exceeds the
sequence number of the DATA packet), causing it to be discarded from the Tx
ring.  The ACK that was requested (labelled REQ, r=xx references the serial
of the DATA packet) comes after the ping, but the sk_buff holding the
timestamp has gone and the RTT sample is lost.

This is particularly noticeable on RPC calls used to probe the service
offered by the peer.  A lot of peers end up with an unknown RTT because we
only ever sent a single RPC.  This confuses the server rotation algorithm.

Fix this by caching the information about the outgoing packet in RTT
calculations in the rxrpc_call struct rather than looking in the Tx ring.

A four-deep buffer is maintained and both REQUEST_ACK-flagged DATA and
PING-ACK transmissions are recorded in there.  When the appropriate
response ACK is received, the buffer is checked for a match and, if found,
an RTT sample is recorded.

If a received ACK refers to a packet with a later serial number than an
entry in the cache, that entry is presumed lost and the entry is made
available to record a new transmission.

ACKs types other than REQUESTED-type and PING-type cause any matching
sample to be cancelled as they don't necessarily represent a useful
measurement.

If there's no space in the buffer on ping/data transmission, the sample
base is discarded.

Fixes: 50235c4b5a2f ("rxrpc: Obtain RTT data by requesting ACKs on DATA packets")
Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/trace/events/rxrpc.h |   27 +++++++++--
 net/rxrpc/ar-internal.h      |   13 +++--
 net/rxrpc/call_object.c      |    1 
 net/rxrpc/input.c            |  104 ++++++++++++++++++++++++------------------
 net/rxrpc/output.c           |   82 +++++++++++++++++++++++++--------
 net/rxrpc/rtt.c              |    3 +
 6 files changed, 154 insertions(+), 76 deletions(-)

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index 059b6e45a028..c33079b986e8 100644
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -138,11 +138,16 @@ enum rxrpc_recvmsg_trace {
 };
 
 enum rxrpc_rtt_tx_trace {
+	rxrpc_rtt_tx_cancel,
 	rxrpc_rtt_tx_data,
+	rxrpc_rtt_tx_no_slot,
 	rxrpc_rtt_tx_ping,
 };
 
 enum rxrpc_rtt_rx_trace {
+	rxrpc_rtt_rx_cancel,
+	rxrpc_rtt_rx_lost,
+	rxrpc_rtt_rx_obsolete,
 	rxrpc_rtt_rx_ping_response,
 	rxrpc_rtt_rx_requested_ack,
 };
@@ -339,10 +344,15 @@ enum rxrpc_tx_point {
 	E_(rxrpc_recvmsg_wait,			"WAIT")
 
 #define rxrpc_rtt_tx_traces \
+	EM(rxrpc_rtt_tx_cancel,			"CNCE") \
 	EM(rxrpc_rtt_tx_data,			"DATA") \
+	EM(rxrpc_rtt_tx_no_slot,		"FULL") \
 	E_(rxrpc_rtt_tx_ping,			"PING")
 
 #define rxrpc_rtt_rx_traces \
+	EM(rxrpc_rtt_rx_cancel,			"CNCL") \
+	EM(rxrpc_rtt_rx_obsolete,		"OBSL") \
+	EM(rxrpc_rtt_rx_lost,			"LOST") \
 	EM(rxrpc_rtt_rx_ping_response,		"PONG") \
 	E_(rxrpc_rtt_rx_requested_ack,		"RACK")
 
@@ -1087,38 +1097,43 @@ TRACE_EVENT(rxrpc_recvmsg,
 
 TRACE_EVENT(rxrpc_rtt_tx,
 	    TP_PROTO(struct rxrpc_call *call, enum rxrpc_rtt_tx_trace why,
-		     rxrpc_serial_t send_serial),
+		     int slot, rxrpc_serial_t send_serial),
 
-	    TP_ARGS(call, why, send_serial),
+	    TP_ARGS(call, why, slot, send_serial),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
 		    __field(enum rxrpc_rtt_tx_trace,	why		)
+		    __field(int,			slot		)
 		    __field(rxrpc_serial_t,		send_serial	)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->call = call->debug_id;
 		    __entry->why = why;
+		    __entry->slot = slot;
 		    __entry->send_serial = send_serial;
 			   ),
 
-	    TP_printk("c=%08x %s sr=%08x",
+	    TP_printk("c=%08x [%d] %s sr=%08x",
 		      __entry->call,
+		      __entry->slot,
 		      __print_symbolic(__entry->why, rxrpc_rtt_tx_traces),
 		      __entry->send_serial)
 	    );
 
 TRACE_EVENT(rxrpc_rtt_rx,
 	    TP_PROTO(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
+		     int slot,
 		     rxrpc_serial_t send_serial, rxrpc_serial_t resp_serial,
 		     u32 rtt, u32 rto),
 
-	    TP_ARGS(call, why, send_serial, resp_serial, rtt, rto),
+	    TP_ARGS(call, why, slot, send_serial, resp_serial, rtt, rto),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
 		    __field(enum rxrpc_rtt_rx_trace,	why		)
+		    __field(int,			slot		)
 		    __field(rxrpc_serial_t,		send_serial	)
 		    __field(rxrpc_serial_t,		resp_serial	)
 		    __field(u32,			rtt		)
@@ -1128,14 +1143,16 @@ TRACE_EVENT(rxrpc_rtt_rx,
 	    TP_fast_assign(
 		    __entry->call = call->debug_id;
 		    __entry->why = why;
+		    __entry->slot = slot;
 		    __entry->send_serial = send_serial;
 		    __entry->resp_serial = resp_serial;
 		    __entry->rtt = rtt;
 		    __entry->rto = rto;
 			   ),
 
-	    TP_printk("c=%08x %s sr=%08x rr=%08x rtt=%u rto=%u",
+	    TP_printk("c=%08x [%d] %s sr=%08x rr=%08x rtt=%u rto=%u",
 		      __entry->call,
+		      __entry->slot,
 		      __print_symbolic(__entry->why, rxrpc_rtt_rx_traces),
 		      __entry->send_serial,
 		      __entry->resp_serial,
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 6d29a3603a3e..884cff7bb169 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -488,7 +488,6 @@ enum rxrpc_call_flag {
 	RXRPC_CALL_RX_LAST,		/* Received the last packet (at rxtx_top) */
 	RXRPC_CALL_TX_LAST,		/* Last packet in Tx buffer (at rxtx_top) */
 	RXRPC_CALL_SEND_PING,		/* A ping will need to be sent */
-	RXRPC_CALL_PINGING,		/* Ping in process */
 	RXRPC_CALL_RETRANS_TIMEOUT,	/* Retransmission due to timeout occurred */
 	RXRPC_CALL_BEGAN_RX_TIMER,	/* We began the expect_rx_by timer */
 	RXRPC_CALL_RX_HEARD,		/* The peer responded at least once to this call */
@@ -673,9 +672,13 @@ struct rxrpc_call {
 	rxrpc_seq_t		ackr_consumed;	/* Highest packet shown consumed */
 	rxrpc_seq_t		ackr_seen;	/* Highest packet shown seen */
 
-	/* ping management */
-	rxrpc_serial_t		ping_serial;	/* Last ping sent */
-	ktime_t			ping_time;	/* Time last ping sent */
+	/* RTT management */
+	rxrpc_serial_t		rtt_serial[4];	/* Serial number of DATA or PING sent */
+	ktime_t			rtt_sent_at[4];	/* Time packet sent */
+	unsigned long		rtt_avail;	/* Mask of available slots in bits 0-3,
+						 * Mask of pending samples in 8-11 */
+#define RXRPC_CALL_RTT_AVAIL_MASK	0xf
+#define RXRPC_CALL_RTT_PEND_SHIFT	8
 
 	/* transmission-phase ACK management */
 	ktime_t			acks_latest_ts;	/* Timestamp of latest ACK received */
@@ -1037,7 +1040,7 @@ static inline bool __rxrpc_abort_eproto(struct rxrpc_call *call,
 /*
  * rtt.c
  */
-void rxrpc_peer_add_rtt(struct rxrpc_call *, enum rxrpc_rtt_rx_trace,
+void rxrpc_peer_add_rtt(struct rxrpc_call *, enum rxrpc_rtt_rx_trace, int,
 			rxrpc_serial_t, rxrpc_serial_t, ktime_t, ktime_t);
 unsigned long rxrpc_get_rto_backoff(struct rxrpc_peer *, bool);
 void rxrpc_peer_init_rtt(struct rxrpc_peer *);
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 38a46167523f..a40fae013942 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -153,6 +153,7 @@ struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp,
 	call->cong_ssthresh = RXRPC_RXTX_BUFF_SIZE - 1;
 
 	call->rxnet = rxnet;
+	call->rtt_avail = RXRPC_CALL_RTT_AVAIL_MASK;
 	atomic_inc(&rxnet->nr_calls);
 	return call;
 
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index a7699e56eac8..19ddfc9807e8 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -608,36 +608,57 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
 }
 
 /*
- * Process a requested ACK.
+ * See if there's a cached RTT probe to complete.
  */
-static void rxrpc_input_requested_ack(struct rxrpc_call *call,
-				      ktime_t resp_time,
-				      rxrpc_serial_t orig_serial,
-				      rxrpc_serial_t ack_serial)
+static void rxrpc_complete_rtt_probe(struct rxrpc_call *call,
+				     ktime_t resp_time,
+				     rxrpc_serial_t acked_serial,
+				     rxrpc_serial_t ack_serial,
+				     enum rxrpc_rtt_rx_trace type)
 {
-	struct rxrpc_skb_priv *sp;
-	struct sk_buff *skb;
+	rxrpc_serial_t orig_serial;
+	unsigned long avail;
 	ktime_t sent_at;
-	int ix;
+	bool matched = false;
+	int i;
 
-	for (ix = 0; ix < RXRPC_RXTX_BUFF_SIZE; ix++) {
-		skb = call->rxtx_buffer[ix];
-		if (!skb)
-			continue;
+	avail = READ_ONCE(call->rtt_avail);
+	smp_rmb(); /* Read avail bits before accessing data. */
 
-		sent_at = skb->tstamp;
-		smp_rmb(); /* Read timestamp before serial. */
-		sp = rxrpc_skb(skb);
-		if (sp->hdr.serial != orig_serial)
+	for (i = 0; i < ARRAY_SIZE(call->rtt_serial); i++) {
+		if (!test_bit(i + RXRPC_CALL_RTT_PEND_SHIFT, &avail))
 			continue;
-		goto found;
-	}
 
-	return;
+		sent_at = call->rtt_sent_at[i];
+		orig_serial = call->rtt_serial[i];
+
+		if (orig_serial == acked_serial) {
+			clear_bit(i + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
+			smp_mb(); /* Read data before setting avail bit */
+			set_bit(i, &call->rtt_avail);
+			if (type != rxrpc_rtt_rx_cancel)
+				rxrpc_peer_add_rtt(call, type, i, acked_serial, ack_serial,
+						   sent_at, resp_time);
+			else
+				trace_rxrpc_rtt_rx(call, rxrpc_rtt_rx_cancel, i,
+						   orig_serial, acked_serial, 0, 0);
+			matched = true;
+		}
+
+		/* If a later serial is being acked, then mark this slot as
+		 * being available.
+		 */
+		if (after(acked_serial, orig_serial)) {
+			trace_rxrpc_rtt_rx(call, rxrpc_rtt_rx_obsolete, i,
+					   orig_serial, acked_serial, 0, 0);
+			clear_bit(i + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
+			smp_wmb();
+			set_bit(i, &call->rtt_avail);
+		}
+	}
 
-found:
-	rxrpc_peer_add_rtt(call, rxrpc_rtt_rx_requested_ack,
-			   orig_serial, ack_serial, sent_at, resp_time);
+	if (!matched)
+		trace_rxrpc_rtt_rx(call, rxrpc_rtt_rx_lost, 9, 0, acked_serial, 0, 0);
 }
 
 /*
@@ -682,27 +703,11 @@ static void rxrpc_input_check_for_lost_ack(struct rxrpc_call *call)
  */
 static void rxrpc_input_ping_response(struct rxrpc_call *call,
 				      ktime_t resp_time,
-				      rxrpc_serial_t orig_serial,
+				      rxrpc_serial_t acked_serial,
 				      rxrpc_serial_t ack_serial)
 {
-	rxrpc_serial_t ping_serial;
-	ktime_t ping_time;
-
-	ping_time = call->ping_time;
-	smp_rmb();
-	ping_serial = READ_ONCE(call->ping_serial);
-
-	if (orig_serial == call->acks_lost_ping)
+	if (acked_serial == call->acks_lost_ping)
 		rxrpc_input_check_for_lost_ack(call);
-
-	if (before(orig_serial, ping_serial) ||
-	    !test_and_clear_bit(RXRPC_CALL_PINGING, &call->flags))
-		return;
-	if (after(orig_serial, ping_serial))
-		return;
-
-	rxrpc_peer_add_rtt(call, rxrpc_rtt_rx_ping_response,
-			   orig_serial, ack_serial, ping_time, resp_time);
 }
 
 /*
@@ -869,12 +874,23 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb)
 			   first_soft_ack, prev_pkt,
 			   summary.ack_reason, nr_acks);
 
-	if (buf.ack.reason == RXRPC_ACK_PING_RESPONSE)
+	switch (buf.ack.reason) {
+	case RXRPC_ACK_PING_RESPONSE:
 		rxrpc_input_ping_response(call, skb->tstamp, acked_serial,
 					  ack_serial);
-	if (buf.ack.reason == RXRPC_ACK_REQUESTED)
-		rxrpc_input_requested_ack(call, skb->tstamp, acked_serial,
-					  ack_serial);
+		rxrpc_complete_rtt_probe(call, skb->tstamp, acked_serial, ack_serial,
+					 rxrpc_rtt_rx_ping_response);
+		break;
+	case RXRPC_ACK_REQUESTED:
+		rxrpc_complete_rtt_probe(call, skb->tstamp, acked_serial, ack_serial,
+					 rxrpc_rtt_rx_requested_ack);
+		break;
+	default:
+		if (acked_serial != 0)
+			rxrpc_complete_rtt_probe(call, skb->tstamp, acked_serial, ack_serial,
+						 rxrpc_rtt_rx_cancel);
+		break;
+	}
 
 	if (buf.ack.reason == RXRPC_ACK_PING) {
 		_proto("Rx ACK %%%u PING Request", ack_serial);
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 1ba43c3df4ad..3cfff7922ba8 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -123,6 +123,49 @@ static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
 	return top - hard_ack + 3;
 }
 
+/*
+ * Record the beginning of an RTT probe.
+ */
+static int rxrpc_begin_rtt_probe(struct rxrpc_call *call, rxrpc_serial_t serial,
+				 enum rxrpc_rtt_tx_trace why)
+{
+	unsigned long avail = call->rtt_avail;
+	int rtt_slot = 9;
+
+	if (!(avail & RXRPC_CALL_RTT_AVAIL_MASK))
+		goto no_slot;
+
+	rtt_slot = __ffs(avail & RXRPC_CALL_RTT_AVAIL_MASK);
+	if (!test_and_clear_bit(rtt_slot, &call->rtt_avail))
+		goto no_slot;
+
+	call->rtt_serial[rtt_slot] = serial;
+	call->rtt_sent_at[rtt_slot] = ktime_get_real();
+	smp_wmb(); /* Write data before avail bit */
+	set_bit(rtt_slot + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
+
+	trace_rxrpc_rtt_tx(call, why, rtt_slot, serial);
+	return rtt_slot;
+
+no_slot:
+	trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_no_slot, rtt_slot, serial);
+	return -1;
+}
+
+/*
+ * Cancel an RTT probe.
+ */
+static void rxrpc_cancel_rtt_probe(struct rxrpc_call *call,
+				   rxrpc_serial_t serial, int rtt_slot)
+{
+	if (rtt_slot != -1) {
+		clear_bit(rtt_slot + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
+		smp_wmb(); /* Clear pending bit before setting slot */
+		set_bit(rtt_slot, &call->rtt_avail);
+		trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_cancel, rtt_slot, serial);
+	}
+}
+
 /*
  * Send an ACK call packet.
  */
@@ -136,7 +179,7 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping,
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top;
 	size_t len, n;
-	int ret;
+	int ret, rtt_slot = -1;
 	u8 reason;
 
 	if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
@@ -196,18 +239,8 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping,
 	if (_serial)
 		*_serial = serial;
 
-	if (ping) {
-		call->ping_serial = serial;
-		smp_wmb();
-		/* We need to stick a time in before we send the packet in case
-		 * the reply gets back before kernel_sendmsg() completes - but
-		 * asking UDP to send the packet can take a relatively long
-		 * time.
-		 */
-		call->ping_time = ktime_get_real();
-		set_bit(RXRPC_CALL_PINGING, &call->flags);
-		trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_ping, serial);
-	}
+	if (ping)
+		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_ping);
 
 	ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 2, len);
 	conn->params.peer->last_tx_at = ktime_get_seconds();
@@ -221,8 +254,7 @@ int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping,
 
 	if (call->state < RXRPC_CALL_COMPLETE) {
 		if (ret < 0) {
-			if (ping)
-				clear_bit(RXRPC_CALL_PINGING, &call->flags);
+			rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
 			rxrpc_propose_ACK(call, pkt->ack.reason,
 					  ntohl(pkt->ack.serial),
 					  false, true,
@@ -321,7 +353,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	struct kvec iov[2];
 	rxrpc_serial_t serial;
 	size_t len;
-	int ret;
+	int ret, rtt_slot = -1;
 
 	_enter(",{%d}", skb->len);
 
@@ -397,6 +429,8 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	sp->hdr.serial = serial;
 	smp_wmb(); /* Set serial before timestamp */
 	skb->tstamp = ktime_get_real();
+	if (whdr.flags & RXRPC_REQUEST_ACK)
+		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_data);
 
 	/* send the packet by UDP
 	 * - returns -EMSGSIZE if UDP would have to fragment the packet
@@ -408,12 +442,15 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	conn->params.peer->last_tx_at = ktime_get_seconds();
 
 	up_read(&conn->params.local->defrag_sem);
-	if (ret < 0)
+	if (ret < 0) {
+		rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_data_nofrag);
-	else
+	} else {
 		trace_rxrpc_tx_packet(call->debug_id, &whdr,
 				      rxrpc_tx_point_call_data_nofrag);
+	}
+
 	rxrpc_tx_backoff(call, ret);
 	if (ret == -EMSGSIZE)
 		goto send_fragmentable;
@@ -422,7 +459,6 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	if (ret >= 0) {
 		if (whdr.flags & RXRPC_REQUEST_ACK) {
 			call->peer->rtt_last_req = skb->tstamp;
-			trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_data, serial);
 			if (call->peer->rtt_count > 1) {
 				unsigned long nowj = jiffies, ack_lost_at;
 
@@ -469,6 +505,8 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	sp->hdr.serial = serial;
 	smp_wmb(); /* Set serial before timestamp */
 	skb->tstamp = ktime_get_real();
+	if (whdr.flags & RXRPC_REQUEST_ACK)
+		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_data);
 
 	switch (conn->params.local->srx.transport.family) {
 	case AF_INET6:
@@ -487,12 +525,14 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 		BUG();
 	}
 
-	if (ret < 0)
+	if (ret < 0) {
+		rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_data_frag);
-	else
+	} else {
 		trace_rxrpc_tx_packet(call->debug_id, &whdr,
 				      rxrpc_tx_point_call_data_frag);
+	}
 	rxrpc_tx_backoff(call, ret);
 
 	up_write(&conn->params.local->defrag_sem);
diff --git a/net/rxrpc/rtt.c b/net/rxrpc/rtt.c
index 928d8b34a3ee..1221b0637a7e 100644
--- a/net/rxrpc/rtt.c
+++ b/net/rxrpc/rtt.c
@@ -146,6 +146,7 @@ static void rxrpc_ack_update_rtt(struct rxrpc_peer *peer, long rtt_us)
  * exclusive access to the peer RTT data.
  */
 void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
+			int rtt_slot,
 			rxrpc_serial_t send_serial, rxrpc_serial_t resp_serial,
 			ktime_t send_time, ktime_t resp_time)
 {
@@ -162,7 +163,7 @@ void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
 		peer->rtt_count++;
 	spin_unlock(&peer->rtt_input_lock);
 
-	trace_rxrpc_rtt_rx(call, why, send_serial, resp_serial,
+	trace_rxrpc_rtt_rx(call, why, rtt_slot, send_serial, resp_serial,
 			   peer->srtt_us >> 3, peer->rto_j);
 }
 

[PATCH net 3/7] rxrpc: Make rxrpc_kernel_get_srtt() indicate validity

[David Howells]

Fix rxrpc_kernel_get_srtt() to indicate the validity of the returned
smoothed RTT.  If we haven't had any valid samples yet, the SRTT isn't
useful.

Fixes: c410bf01933e ("rxrpc: Fix the excessive initial retransmission timeout")
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/fs_probe.c       |    4 ++--
 fs/afs/vl_probe.c       |    4 ++--
 include/net/af_rxrpc.h  |    2 +-
 net/rxrpc/peer_object.c |   16 +++++++++++++---
 4 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c
index 5d9ef517cf81..e7e98ad63a91 100644
--- a/fs/afs/fs_probe.c
+++ b/fs/afs/fs_probe.c
@@ -161,8 +161,8 @@ void afs_fileserver_probe_result(struct afs_call *call)
 		}
 	}
 
-	rtt_us = rxrpc_kernel_get_srtt(call->net->socket, call->rxcall);
-	if (rtt_us < server->probe.rtt) {
+	if (rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us) &&
+	    rtt_us < server->probe.rtt) {
 		server->probe.rtt = rtt_us;
 		server->rtt = rtt_us;
 		alist->preferred = index;
diff --git a/fs/afs/vl_probe.c b/fs/afs/vl_probe.c
index e3aa013c2177..081b7e5b13f5 100644
--- a/fs/afs/vl_probe.c
+++ b/fs/afs/vl_probe.c
@@ -92,8 +92,8 @@ void afs_vlserver_probe_result(struct afs_call *call)
 		}
 	}
 
-	rtt_us = rxrpc_kernel_get_srtt(call->net->socket, call->rxcall);
-	if (rtt_us < server->probe.rtt) {
+	if (rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us) &&
+	    rtt_us < server->probe.rtt) {
 		server->probe.rtt = rtt_us;
 		alist->preferred = index;
 		have_result = true;
diff --git a/include/net/af_rxrpc.h b/include/net/af_rxrpc.h
index 91eacbdcf33d..f6abcc0bbd6e 100644
--- a/include/net/af_rxrpc.h
+++ b/include/net/af_rxrpc.h
@@ -59,7 +59,7 @@ bool rxrpc_kernel_abort_call(struct socket *, struct rxrpc_call *,
 void rxrpc_kernel_end_call(struct socket *, struct rxrpc_call *);
 void rxrpc_kernel_get_peer(struct socket *, struct rxrpc_call *,
 			   struct sockaddr_rxrpc *);
-u32 rxrpc_kernel_get_srtt(struct socket *, struct rxrpc_call *);
+bool rxrpc_kernel_get_srtt(struct socket *, struct rxrpc_call *, u32 *);
 int rxrpc_kernel_charge_accept(struct socket *, rxrpc_notify_rx_t,
 			       rxrpc_user_attach_call_t, unsigned long, gfp_t,
 			       unsigned int);
diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index ca29976bb193..68396d052052 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -502,11 +502,21 @@ EXPORT_SYMBOL(rxrpc_kernel_get_peer);
  * rxrpc_kernel_get_srtt - Get a call's peer smoothed RTT
  * @sock: The socket on which the call is in progress.
  * @call: The call to query
+ * @_srtt: Where to store the SRTT value.
  *
- * Get the call's peer smoothed RTT.
+ * Get the call's peer smoothed RTT in uS.
  */
-u32 rxrpc_kernel_get_srtt(struct socket *sock, struct rxrpc_call *call)
+bool rxrpc_kernel_get_srtt(struct socket *sock, struct rxrpc_call *call,
+			   u32 *_srtt)
 {
-	return call->peer->srtt_us >> 3;
+	struct rxrpc_peer *peer = call->peer;
+
+	if (peer->rtt_count == 0) {
+		*_srtt = 1000000; /* 1S */
+		return false;
+	}
+
+	*_srtt = call->peer->srtt_us >> 3;
+	return true;
 }
 EXPORT_SYMBOL(rxrpc_kernel_get_srtt);

[PATCH net 4/7] afs: Remove afs_vlserver->probe.have_result

[David Howells]

Remove afs_vlserver->probe.have_result as it's neither read nor waited
upon.

Fixes: 3bf0fb6f33dd ("afs: Probe multiple fileservers simultaneously")
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/internal.h |    1 -
 fs/afs/vl_probe.c |    5 +----
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 792ac711985e..2e6ae6388c72 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -412,7 +412,6 @@ struct afs_vlserver {
 		unsigned int	rtt;		/* RTT as ktime/64 */
 		u32		abort_code;
 		short		error;
-		bool		have_result;
 		bool		responded:1;
 		bool		is_yfs:1;
 		bool		not_yfs:1;
diff --git a/fs/afs/vl_probe.c b/fs/afs/vl_probe.c
index 081b7e5b13f5..ee59188433b9 100644
--- a/fs/afs/vl_probe.c
+++ b/fs/afs/vl_probe.c
@@ -109,11 +109,8 @@ void afs_vlserver_probe_result(struct afs_call *call)
 	       server_index, index, &alist->addrs[index].transport, rtt_us, ret);
 
 	have_result |= afs_vl_probe_done(server);
-	if (have_result) {
-		server->probe.have_result = true;
-		wake_up_var(&server->probe.have_result);
+	if (have_result)
 		wake_up_all(&server->probe_wq);
-	}
 }
 
 /*

[PATCH net 5/7] afs: Expose information from afs_vlserver through /proc for debugging

[David Howells]

Convert various bitfields in afs_vlserver::probe to a mask and then expose
this and some other bits of information through /proc/net/afs/<cell>/vlservers
to make it easier to debug VL server communication issues.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/internal.h  |    9 +++++----
 fs/afs/proc.c      |    5 +++++
 fs/afs/vl_probe.c  |   20 ++++++++++----------
 fs/afs/vl_rotate.c |    3 ++-
 4 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 2e6ae6388c72..b29dfcfe5fc2 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -412,10 +412,11 @@ struct afs_vlserver {
 		unsigned int	rtt;		/* RTT as ktime/64 */
 		u32		abort_code;
 		short		error;
-		bool		responded:1;
-		bool		is_yfs:1;
-		bool		not_yfs:1;
-		bool		local_failure:1;
+		unsigned short	flags;
+#define AFS_VLSERVER_PROBE_RESPONDED		0x01 /* At least once response (may be abort) */
+#define AFS_VLSERVER_PROBE_IS_YFS		0x02 /* The peer appears to be YFS */
+#define AFS_VLSERVER_PROBE_NOT_YFS		0x04 /* The peer appears not to be YFS */
+#define AFS_VLSERVER_PROBE_LOCAL_FAILURE	0x08 /* A local failure prevented a probe */
 	} probe;
 
 	u16			port;
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index e817fc740ba0..5e837155f1a0 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -310,6 +310,11 @@ static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v)
 				   alist->preferred == i ? '>' : '-',
 				   &alist->addrs[i].transport);
 	}
+	seq_printf(m, " info: fl=%lx rtt=%d\n", vlserver->flags, vlserver->probe.rtt);
+	seq_printf(m, " probe: fl=%x e=%d ac=%d out=%d\n",
+		   vlserver->probe.flags, vlserver->probe.error,
+		   vlserver->probe.abort_code,
+		   atomic_read(&vlserver->probe_outstanding));
 	return 0;
 }
 
diff --git a/fs/afs/vl_probe.c b/fs/afs/vl_probe.c
index ee59188433b9..a6d04b4fbf56 100644
--- a/fs/afs/vl_probe.c
+++ b/fs/afs/vl_probe.c
@@ -45,14 +45,14 @@ void afs_vlserver_probe_result(struct afs_call *call)
 		server->probe.error = 0;
 		goto responded;
 	case -ECONNABORTED:
-		if (!server->probe.responded) {
+		if (!(server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED)) {
 			server->probe.abort_code = call->abort_code;
 			server->probe.error = ret;
 		}
 		goto responded;
 	case -ENOMEM:
 	case -ENONET:
-		server->probe.local_failure = true;
+		server->probe.flags |= AFS_VLSERVER_PROBE_LOCAL_FAILURE;
 		afs_io_error(call, afs_io_error_vl_probe_fail);
 		goto out;
 	case -ECONNRESET: /* Responded, but call expired. */
@@ -67,7 +67,7 @@ void afs_vlserver_probe_result(struct afs_call *call)
 	default:
 		clear_bit(index, &alist->responded);
 		set_bit(index, &alist->failed);
-		if (!server->probe.responded &&
+		if (!(server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED) &&
 		    (server->probe.error == 0 ||
 		     server->probe.error == -ETIMEDOUT ||
 		     server->probe.error == -ETIME))
@@ -81,12 +81,12 @@ void afs_vlserver_probe_result(struct afs_call *call)
 	clear_bit(index, &alist->failed);
 
 	if (call->service_id == YFS_VL_SERVICE) {
-		server->probe.is_yfs = true;
+		server->probe.flags |= AFS_VLSERVER_PROBE_IS_YFS;
 		set_bit(AFS_VLSERVER_FL_IS_YFS, &server->flags);
 		alist->addrs[index].srx_service = call->service_id;
 	} else {
-		server->probe.not_yfs = true;
-		if (!server->probe.is_yfs) {
+		server->probe.flags |= AFS_VLSERVER_PROBE_NOT_YFS;
+		if (!(server->probe.flags & AFS_VLSERVER_PROBE_IS_YFS)) {
 			clear_bit(AFS_VLSERVER_FL_IS_YFS, &server->flags);
 			alist->addrs[index].srx_service = call->service_id;
 		}
@@ -100,7 +100,7 @@ void afs_vlserver_probe_result(struct afs_call *call)
 	}
 
 	smp_wmb(); /* Set rtt before responded. */
-	server->probe.responded = true;
+	server->probe.flags |= AFS_VLSERVER_PROBE_RESPONDED;
 	set_bit(AFS_VLSERVER_FL_PROBED, &server->flags);
 out:
 	spin_unlock(&server->probe_lock);
@@ -202,7 +202,7 @@ int afs_wait_for_vl_probes(struct afs_vlserver_list *vllist,
 			server = vllist->servers[i].server;
 			if (!test_bit(AFS_VLSERVER_FL_PROBING, &server->flags))
 				__clear_bit(i, &untried);
-			if (server->probe.responded)
+			if (server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED)
 				have_responders = true;
 		}
 	}
@@ -228,7 +228,7 @@ int afs_wait_for_vl_probes(struct afs_vlserver_list *vllist,
 		for (i = 0; i < vllist->nr_servers; i++) {
 			if (test_bit(i, &untried)) {
 				server = vllist->servers[i].server;
-				if (server->probe.responded)
+				if (server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED)
 					goto stop;
 				if (test_bit(AFS_VLSERVER_FL_PROBING, &server->flags))
 					still_probing = true;
@@ -246,7 +246,7 @@ int afs_wait_for_vl_probes(struct afs_vlserver_list *vllist,
 	for (i = 0; i < vllist->nr_servers; i++) {
 		if (test_bit(i, &untried)) {
 			server = vllist->servers[i].server;
-			if (server->probe.responded &&
+			if ((server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED) &&
 			    server->probe.rtt < rtt) {
 				pref = i;
 				rtt = server->probe.rtt;
diff --git a/fs/afs/vl_rotate.c b/fs/afs/vl_rotate.c
index f405ca8b240a..ed2609e82695 100644
--- a/fs/afs/vl_rotate.c
+++ b/fs/afs/vl_rotate.c
@@ -192,7 +192,8 @@ bool afs_select_vlserver(struct afs_vl_cursor *vc)
 	for (i = 0; i < vc->server_list->nr_servers; i++) {
 		struct afs_vlserver *s = vc->server_list->servers[i].server;
 
-		if (!test_bit(i, &vc->untried) || !s->probe.responded)
+		if (!test_bit(i, &vc->untried) ||
+		    !(s->probe.flags & AFS_VLSERVER_PROBE_RESPONDED))
 			continue;
 		if (s->probe.rtt < rtt) {
 			vc->index = i;

[PATCH net 6/7] afs: Don't use VL probe running state to make decisions outside probe code

[David Howells]

Don't use the running state for VL server probes to make decisions about
which server to use as the state is cleared at the start of a probe and
intermediate values might also be misleading.

Instead, add a separate 'latest known' rtt in the afs_vlserver struct and a
flag to indicate if the server is known to be responding and update these
as and when we know what to change them to.

Fixes: 3bf0fb6f33dd ("afs: Probe multiple fileservers simultaneously")
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/internal.h  |    4 +++-
 fs/afs/proc.c      |    2 +-
 fs/afs/vl_list.c   |    1 +
 fs/afs/vl_probe.c  |   57 ++++++++++++++++++++++++++++++++++++----------------
 fs/afs/vl_rotate.c |    2 +-
 5 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index b29dfcfe5fc2..18042b7dab6a 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -401,15 +401,17 @@ struct afs_vlserver {
 #define AFS_VLSERVER_FL_PROBED	0		/* The VL server has been probed */
 #define AFS_VLSERVER_FL_PROBING	1		/* VL server is being probed */
 #define AFS_VLSERVER_FL_IS_YFS	2		/* Server is YFS not AFS */
+#define AFS_VLSERVER_FL_RESPONDING 3		/* VL server is responding */
 	rwlock_t		lock;		/* Lock on addresses */
 	atomic_t		usage;
+	unsigned int		rtt;		/* Server's current RTT in uS */
 
 	/* Probe state */
 	wait_queue_head_t	probe_wq;
 	atomic_t		probe_outstanding;
 	spinlock_t		probe_lock;
 	struct {
-		unsigned int	rtt;		/* RTT as ktime/64 */
+		unsigned int	rtt;		/* RTT in uS */
 		u32		abort_code;
 		short		error;
 		unsigned short	flags;
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index 5e837155f1a0..e8babb62ed44 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -310,7 +310,7 @@ static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v)
 				   alist->preferred == i ? '>' : '-',
 				   &alist->addrs[i].transport);
 	}
-	seq_printf(m, " info: fl=%lx rtt=%d\n", vlserver->flags, vlserver->probe.rtt);
+	seq_printf(m, " info: fl=%lx rtt=%d\n", vlserver->flags, vlserver->rtt);
 	seq_printf(m, " probe: fl=%x e=%d ac=%d out=%d\n",
 		   vlserver->probe.flags, vlserver->probe.error,
 		   vlserver->probe.abort_code,
diff --git a/fs/afs/vl_list.c b/fs/afs/vl_list.c
index 8fea54eba0c2..38b2ba1d9ec0 100644
--- a/fs/afs/vl_list.c
+++ b/fs/afs/vl_list.c
@@ -21,6 +21,7 @@ struct afs_vlserver *afs_alloc_vlserver(const char *name, size_t name_len,
 		rwlock_init(&vlserver->lock);
 		init_waitqueue_head(&vlserver->probe_wq);
 		spin_lock_init(&vlserver->probe_lock);
+		vlserver->rtt = UINT_MAX;
 		vlserver->name_len = name_len;
 		vlserver->port = port;
 		memcpy(vlserver->name, name, name_len);
diff --git a/fs/afs/vl_probe.c b/fs/afs/vl_probe.c
index a6d04b4fbf56..d1c7068b4346 100644
--- a/fs/afs/vl_probe.c
+++ b/fs/afs/vl_probe.c
@@ -11,15 +11,33 @@
 #include "internal.h"
 #include "protocol_yfs.h"
 
-static bool afs_vl_probe_done(struct afs_vlserver *server)
+
+/*
+ * Handle the completion of a set of probes.
+ */
+static void afs_finished_vl_probe(struct afs_vlserver *server)
 {
-	if (!atomic_dec_and_test(&server->probe_outstanding))
-		return false;
+	if (!(server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED)) {
+		server->rtt = UINT_MAX;
+		clear_bit(AFS_VLSERVER_FL_RESPONDING, &server->flags);
+	}
 
-	wake_up_var(&server->probe_outstanding);
 	clear_bit_unlock(AFS_VLSERVER_FL_PROBING, &server->flags);
 	wake_up_bit(&server->flags, AFS_VLSERVER_FL_PROBING);
-	return true;
+}
+
+/*
+ * Handle the completion of a probe RPC call.
+ */
+static void afs_done_one_vl_probe(struct afs_vlserver *server, bool wake_up)
+{
+	if (atomic_dec_and_test(&server->probe_outstanding)) {
+		afs_finished_vl_probe(server);
+		wake_up = true;
+	}
+
+	if (wake_up)
+		wake_up_all(&server->probe_wq);
 }
 
 /*
@@ -52,8 +70,13 @@ void afs_vlserver_probe_result(struct afs_call *call)
 		goto responded;
 	case -ENOMEM:
 	case -ENONET:
+	case -EKEYEXPIRED:
+	case -EKEYREVOKED:
+	case -EKEYREJECTED:
 		server->probe.flags |= AFS_VLSERVER_PROBE_LOCAL_FAILURE;
-		afs_io_error(call, afs_io_error_vl_probe_fail);
+		if (server->probe.error == 0)
+			server->probe.error = ret;
+		trace_afs_io_error(call->debug_id, ret, afs_io_error_vl_probe_fail);
 		goto out;
 	case -ECONNRESET: /* Responded, but call expired. */
 	case -ERFKILL:
@@ -72,7 +95,7 @@ void afs_vlserver_probe_result(struct afs_call *call)
 		     server->probe.error == -ETIMEDOUT ||
 		     server->probe.error == -ETIME))
 			server->probe.error = ret;
-		afs_io_error(call, afs_io_error_vl_probe_fail);
+		trace_afs_io_error(call->debug_id, ret, afs_io_error_vl_probe_fail);
 		goto out;
 	}
 
@@ -95,22 +118,22 @@ void afs_vlserver_probe_result(struct afs_call *call)
 	if (rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us) &&
 	    rtt_us < server->probe.rtt) {
 		server->probe.rtt = rtt_us;
+		server->rtt = rtt_us;
 		alist->preferred = index;
-		have_result = true;
 	}
 
 	smp_wmb(); /* Set rtt before responded. */
 	server->probe.flags |= AFS_VLSERVER_PROBE_RESPONDED;
 	set_bit(AFS_VLSERVER_FL_PROBED, &server->flags);
+	set_bit(AFS_VLSERVER_FL_RESPONDING, &server->flags);
+	have_result = true;
 out:
 	spin_unlock(&server->probe_lock);
 
 	_debug("probe [%u][%u] %pISpc rtt=%u ret=%d",
 	       server_index, index, &alist->addrs[index].transport, rtt_us, ret);
 
-	have_result |= afs_vl_probe_done(server);
-	if (have_result)
-		wake_up_all(&server->probe_wq);
+	afs_done_one_vl_probe(server, have_result);
 }
 
 /*
@@ -148,11 +171,10 @@ static bool afs_do_probe_vlserver(struct afs_net *net,
 			in_progress = true;
 		} else {
 			afs_prioritise_error(_e, PTR_ERR(call), ac.abort_code);
+			afs_done_one_vl_probe(server, false);
 		}
 	}
 
-	if (!in_progress)
-		afs_vl_probe_done(server);
 	return in_progress;
 }
 
@@ -190,7 +212,7 @@ int afs_wait_for_vl_probes(struct afs_vlserver_list *vllist,
 {
 	struct wait_queue_entry *waits;
 	struct afs_vlserver *server;
-	unsigned int rtt = UINT_MAX;
+	unsigned int rtt = UINT_MAX, rtt_s;
 	bool have_responders = false;
 	int pref = -1, i;
 
@@ -246,10 +268,11 @@ int afs_wait_for_vl_probes(struct afs_vlserver_list *vllist,
 	for (i = 0; i < vllist->nr_servers; i++) {
 		if (test_bit(i, &untried)) {
 			server = vllist->servers[i].server;
-			if ((server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED) &&
-			    server->probe.rtt < rtt) {
+			rtt_s = READ_ONCE(server->rtt);
+			if (test_bit(AFS_VLSERVER_FL_RESPONDING, &server->flags) &&
+			    rtt_s < rtt) {
 				pref = i;
-				rtt = server->probe.rtt;
+				rtt = rtt_s;
 			}
 
 			remove_wait_queue(&server->probe_wq, &waits[i]);
diff --git a/fs/afs/vl_rotate.c b/fs/afs/vl_rotate.c
index ed2609e82695..ab2beb4ba20e 100644
--- a/fs/afs/vl_rotate.c
+++ b/fs/afs/vl_rotate.c
@@ -193,7 +193,7 @@ bool afs_select_vlserver(struct afs_vl_cursor *vc)
 		struct afs_vlserver *s = vc->server_list->servers[i].server;
 
 		if (!test_bit(i, &vc->untried) ||
-		    !(s->probe.flags & AFS_VLSERVER_PROBE_RESPONDED))
+		    !test_bit(AFS_VLSERVER_FL_RESPONDING, &s->flags))
 			continue;
 		if (s->probe.rtt < rtt) {
 			vc->index = i;

[PATCH net 7/7] afs: Fix error handling in VL server rotation

[David Howells]

The error handling in the VL server rotation in the case of there being no
contactable servers is not correct.  In such a case, the records of all the
servers in the list are scanned and the errors and abort codes are mapped
and prioritised and one error is chosen.  This is then forgotten and the
default error is used (EDESTADDRREQ).

Fix this by using the calculated error.

Also we need to note whether a server responded on one of its endpoints so
that we can priorise an error from an abort message over local and network
errors.

Fixes: 4584ae96ae30 ("afs: Fix missing net error handling")
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/vl_rotate.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/afs/vl_rotate.c b/fs/afs/vl_rotate.c
index ab2beb4ba20e..c0458c903b31 100644
--- a/fs/afs/vl_rotate.c
+++ b/fs/afs/vl_rotate.c
@@ -263,10 +263,14 @@ bool afs_select_vlserver(struct afs_vl_cursor *vc)
 	for (i = 0; i < vc->server_list->nr_servers; i++) {
 		struct afs_vlserver *s = vc->server_list->servers[i].server;
 
+		if (test_bit(AFS_VLSERVER_FL_RESPONDING, &s->flags))
+			e.responded = true;
 		afs_prioritise_error(&e, READ_ONCE(s->probe.error),
 				     s->probe.abort_code);
 	}
 
+	error = e.error;
+
 failed_set_error:
 	vc->error = error;
 failed:

Re: [PATCH net 0/7] rxrpc, afs: Fix probing issues

[David Miller]

From: David Howells <dhowells@redhat.com>
Date: Thu, 27 Aug 2020 16:03:33 +0100

> 
> Here are some fixes for rxrpc and afs to fix issues in the RTT measuring in
> rxrpc and thence the Volume Location server probing in afs:
> 
>  (1) Move the serial number of a received ACK into a local variable to
>      simplify the next patch.
> 
>  (2) Fix the loss of RTT samples due to extra interposed ACKs causing
>      baseline information to be discarded too early.  This is a particular
>      problem for afs when it sends a single very short call to probe a
>      server it hasn't talked to recently.
> 
>  (3) Fix rxrpc_kernel_get_srtt() to indicate whether it actually has seen
>      any valid samples or not.
> 
>  (4) Remove a field that's set/woken, but never read/waited on.
> 
>  (5) Expose the RTT and other probe information through procfs to make
>      debugging of this stuff easier.
> 
>  (6) Fix VL rotation in afs to only use summary information from VL probing
>      and not the probe running state (which gets clobbered when next a
>      probe is issued).
> 
>  (7) Fix VL rotation to actually return the error aggregated from the probe
>      errors.
> 
> The patches are tagged here:
> 
> 	git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
> 	rxrpc-fixes-20200820

Pulled, thanks David.