afs: Don't use VL probe running state to make decisions outside probe code

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: 3bf0fb6f ("afs: Probe multiple fileservers simultaneously")
Signed-off-by: David Howells <dhowells@redhat.com>

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;

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,

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);

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]);

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;