fs/afs/fs_probe.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* AFS fileserver probing
  *
  * Copyright (C) 2018, 2020 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

 #include <linux/sched.h>
 #include <linux/slab.h>
 #include "afs_fs.h"
 #include "internal.h"
 #include "protocol_afs.h"
 #include "protocol_yfs.h"

 static unsigned int afs_fs_probe_fast_poll_interval = 30 * HZ;
 static unsigned int afs_fs_probe_slow_poll_interval = 5 * 60 * HZ;

 /*
  * Start the probe polling timer.  We have to supply it with an inc on the
  * outstanding server count.
  */
 static void afs_schedule_fs_probe(struct afs_net *net,
 				  struct afs_server *server, bool fast)
 {
 	unsigned long atj;

 	if (!net->live)
 		return;

 	atj = server->probed_at;
 	atj += fast ? afs_fs_probe_fast_poll_interval : afs_fs_probe_slow_poll_interval;

 	afs_inc_servers_outstanding(net);
 	if (timer_reduce(&net->fs_probe_timer, atj))
 		afs_dec_servers_outstanding(net);
 }

 /*
  * Handle the completion of a set of probes.
  */
 static void afs_finished_fs_probe(struct afs_net *net, struct afs_server *server)
 {
 	bool responded = server->probe.responded;

 	write_seqlock(&net->fs_lock);
 	if (responded) {
 		list_add_tail(&server->probe_link, &net->fs_probe_slow);
 	} else {
 		server->rtt = UINT_MAX;
 		clear_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
 		list_add_tail(&server->probe_link, &net->fs_probe_fast);
 	}
 	write_sequnlock(&net->fs_lock);

 	afs_schedule_fs_probe(net, server, !responded);
 }

 /*
  * Handle the completion of a probe.
  */
 static void afs_done_one_fs_probe(struct afs_net *net, struct afs_server *server)
 {
 	_enter("");

 	if (atomic_dec_and_test(&server->probe_outstanding))
 		afs_finished_fs_probe(net, server);

 	wake_up_all(&server->probe_wq);
 }

 /*
  * Handle inability to send a probe due to ENOMEM when trying to allocate a
  * call struct.
  */
 static void afs_fs_probe_not_done(struct afs_net *net,
 				  struct afs_server *server,
 				  struct afs_addr_cursor *ac)
 {
 	struct afs_addr_list *alist = ac->alist;
 	unsigned int index = ac->index;

 	_enter("");

 	trace_afs_io_error(0, -ENOMEM, afs_io_error_fs_probe_fail);
 	spin_lock(&server->probe_lock);

 	server->probe.local_failure = true;
 	if (server->probe.error == 0)
 		server->probe.error = -ENOMEM;

 	set_bit(index, &alist->failed);

 	spin_unlock(&server->probe_lock);
 	return afs_done_one_fs_probe(net, server);
 }

 /*
  * Process the result of probing a fileserver.  This is called after successful
  * or failed delivery of an FS.GetCapabilities operation.
  */
 void afs_fileserver_probe_result(struct afs_call *call)
 {
 	struct afs_addr_list *alist = call->alist;
 	struct afs_server *server = call->server;
 	unsigned int index = call->addr_ix;
 	unsigned int rtt_us = 0, cap0;
 	int ret = call->error;

 	_enter("%pU,%u", &server->uuid, index);

 	spin_lock(&server->probe_lock);

 	switch (ret) {
 	case 0:
 		server->probe.error = 0;
 		goto responded;
 	case -ECONNABORTED:
 		if (!server->probe.responded) {
 			server->probe.abort_code = call->abort_code;
 			server->probe.error = ret;
 		}
 		goto responded;
 	case -ENOMEM:
 	case -ENONET:
 		clear_bit(index, &alist->responded);
 		server->probe.local_failure = true;
 		trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_probe_fail);
 		goto out;
 	case -ECONNRESET: /* Responded, but call expired. */
 	case -ERFKILL:
 	case -EADDRNOTAVAIL:
 	case -ENETUNREACH:
 	case -EHOSTUNREACH:
 	case -EHOSTDOWN:
 	case -ECONNREFUSED:
 	case -ETIMEDOUT:
 	case -ETIME:
 	default:
 		clear_bit(index, &alist->responded);
 		set_bit(index, &alist->failed);
 		if (!server->probe.responded &&
 		    (server->probe.error == 0 ||
 		     server->probe.error == -ETIMEDOUT ||
 		     server->probe.error == -ETIME))
 			server->probe.error = ret;
 		trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_probe_fail);
 		goto out;
 	}

 responded:
 	clear_bit(index, &alist->failed);

 	if (call->service_id == YFS_FS_SERVICE) {
 		server->probe.is_yfs = true;
 		set_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
 		alist->addrs[index].srx_service = call->service_id;
 	} else {
 		server->probe.not_yfs = true;
 		if (!server->probe.is_yfs) {
 			clear_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
 			alist->addrs[index].srx_service = call->service_id;
 		}
 		cap0 = ntohl(call->tmp);
 		if (cap0 & AFS3_VICED_CAPABILITY_64BITFILES)
 			set_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
 		else
 			clear_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
 	}

 	rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us);
 	if (rtt_us < server->probe.rtt) {
 		server->probe.rtt = rtt_us;
 		server->rtt = rtt_us;
 		alist->preferred = index;
 	}

 	smp_wmb(); /* Set rtt before responded. */
 	server->probe.responded = true;
 	set_bit(index, &alist->responded);
 	set_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
 out:
 	spin_unlock(&server->probe_lock);

 	_debug("probe %pU [%u] %pISpc rtt=%u ret=%d",
 	       &server->uuid, index, &alist->addrs[index].transport,
 	       rtt_us, ret);

 	return afs_done_one_fs_probe(call->net, server);
 }

 /*
  * Probe one or all of a fileserver's addresses to find out the best route and
  * to query its capabilities.
  */
 void afs_fs_probe_fileserver(struct afs_net *net, struct afs_server *server,
 			     struct key *key, bool all)
 {
 	struct afs_addr_cursor ac = {
 		.index = 0,
 	};

 	_enter("%pU", &server->uuid);

 	read_lock(&server->fs_lock);
 	ac.alist = rcu_dereference_protected(server->addresses,
 					     lockdep_is_held(&server->fs_lock));
 	afs_get_addrlist(ac.alist);
 	read_unlock(&server->fs_lock);

 	server->probed_at = jiffies;
 	atomic_set(&server->probe_outstanding, all ? ac.alist->nr_addrs : 1);
 	memset(&server->probe, 0, sizeof(server->probe));
 	server->probe.rtt = UINT_MAX;

 	ac.index = ac.alist->preferred;
 	if (ac.index < 0 || ac.index >= ac.alist->nr_addrs)
 		all = true;

 	if (all) {
 		for (ac.index = 0; ac.index < ac.alist->nr_addrs; ac.index++)
 			if (!afs_fs_get_capabilities(net, server, &ac, key))
 				afs_fs_probe_not_done(net, server, &ac);
 	} else {
 		if (!afs_fs_get_capabilities(net, server, &ac, key))
 			afs_fs_probe_not_done(net, server, &ac);
 	}

 	afs_put_addrlist(ac.alist);
 }

 /*
  * Wait for the first as-yet untried fileserver to respond.
  */
 int afs_wait_for_fs_probes(struct afs_server_list *slist, unsigned long untried)
 {
 	struct wait_queue_entry *waits;
 	struct afs_server *server;
 	unsigned int rtt = UINT_MAX, rtt_s;
 	bool have_responders = false;
 	int pref = -1, i;

 	_enter("%u,%lx", slist->nr_servers, untried);

 	/* Only wait for servers that have a probe outstanding. */
 	for (i = 0; i < slist->nr_servers; i++) {
 		if (test_bit(i, &untried)) {
 			server = slist->servers[i].server;
 			if (!atomic_read(&server->probe_outstanding))
 				__clear_bit(i, &untried);
 			if (server->probe.responded)
 				have_responders = true;
 		}
 	}
 	if (have_responders || !untried)
 		return 0;

 	waits = kmalloc(array_size(slist->nr_servers, sizeof(*waits)), GFP_KERNEL);
 	if (!waits)
 		return -ENOMEM;

 	for (i = 0; i < slist->nr_servers; i++) {
 		if (test_bit(i, &untried)) {
 			server = slist->servers[i].server;
 			init_waitqueue_entry(&waits[i], current);
 			add_wait_queue(&server->probe_wq, &waits[i]);
 		}
 	}

 	for (;;) {
 		bool still_probing = false;

 		set_current_state(TASK_INTERRUPTIBLE);
 		for (i = 0; i < slist->nr_servers; i++) {
 			if (test_bit(i, &untried)) {
 				server = slist->servers[i].server;
 				if (server->probe.responded)
 					goto stop;
 				if (atomic_read(&server->probe_outstanding))
 					still_probing = true;
 			}
 		}

 		if (!still_probing || signal_pending(current))
 			goto stop;
 		schedule();
 	}

 stop:
 	set_current_state(TASK_RUNNING);

 	for (i = 0; i < slist->nr_servers; i++) {
 		if (test_bit(i, &untried)) {
 			server = slist->servers[i].server;
 			rtt_s = READ_ONCE(server->rtt);
 			if (test_bit(AFS_SERVER_FL_RESPONDING, &server->flags) &&
 			    rtt_s < rtt) {
 				pref = i;
 				rtt = rtt_s;
 			}

 			remove_wait_queue(&server->probe_wq, &waits[i]);
 		}
 	}

 	kfree(waits);

 	if (pref == -1 && signal_pending(current))
 		return -ERESTARTSYS;

 	if (pref >= 0)
 		slist->preferred = pref;
 	return 0;
 }

 /*
  * Probe timer.  We have an increment on fs_outstanding that we need to pass
  * along to the work item.
  */
 void afs_fs_probe_timer(struct timer_list *timer)
 {
 	struct afs_net *net = container_of(timer, struct afs_net, fs_probe_timer);

 	if (!net->live || !queue_work(afs_wq, &net->fs_prober))
 		afs_dec_servers_outstanding(net);
 }

 /*
  * Dispatch a probe to a server.
  */
 static void afs_dispatch_fs_probe(struct afs_net *net, struct afs_server *server, bool all)
 	__releases(&net->fs_lock)
 {
 	struct key *key = NULL;

 	/* We remove it from the queues here - it will be added back to
 	 * one of the queues on the completion of the probe.
 	 */
 	list_del_init(&server->probe_link);

 	afs_get_server(server, afs_server_trace_get_probe);
 	write_sequnlock(&net->fs_lock);

 	afs_fs_probe_fileserver(net, server, key, all);
 	afs_put_server(net, server, afs_server_trace_put_probe);
 }

 /*
  * Probe a server immediately without waiting for its due time to come
  * round.  This is used when all of the addresses have been tried.
  */
 void afs_probe_fileserver(struct afs_net *net, struct afs_server *server)
 {
 	write_seqlock(&net->fs_lock);
 	if (!list_empty(&server->probe_link))
 		return afs_dispatch_fs_probe(net, server, true);
 	write_sequnlock(&net->fs_lock);
 }

 /*
  * Probe dispatcher to regularly dispatch probes to keep NAT alive.
  */
 void afs_fs_probe_dispatcher(struct work_struct *work)
 {
 	struct afs_net *net = container_of(work, struct afs_net, fs_prober);
 	struct afs_server *fast, *slow, *server;
 	unsigned long nowj, timer_at, poll_at;
 	bool first_pass = true, set_timer = false;

 	if (!net->live) {
 		afs_dec_servers_outstanding(net);
 		return;
 	}

 	_enter("");

 	if (list_empty(&net->fs_probe_fast) && list_empty(&net->fs_probe_slow)) {
 		afs_dec_servers_outstanding(net);
 		_leave(" [none]");
 		return;
 	}

 again:
 	write_seqlock(&net->fs_lock);

 	fast = slow = server = NULL;
 	nowj = jiffies;
 	timer_at = nowj + MAX_JIFFY_OFFSET;

 	if (!list_empty(&net->fs_probe_fast)) {
 		fast = list_first_entry(&net->fs_probe_fast, struct afs_server, probe_link);
 		poll_at = fast->probed_at + afs_fs_probe_fast_poll_interval;
 		if (time_before(nowj, poll_at)) {
 			timer_at = poll_at;
 			set_timer = true;
 			fast = NULL;
 		}
 	}

 	if (!list_empty(&net->fs_probe_slow)) {
 		slow = list_first_entry(&net->fs_probe_slow, struct afs_server, probe_link);
 		poll_at = slow->probed_at + afs_fs_probe_slow_poll_interval;
 		if (time_before(nowj, poll_at)) {
 			if (time_before(poll_at, timer_at))
 			    timer_at = poll_at;
 			set_timer = true;
 			slow = NULL;
 		}
 	}

 	server = fast ?: slow;
 	if (server)
 		_debug("probe %pU", &server->uuid);

 	if (server && (first_pass || !need_resched())) {
 		afs_dispatch_fs_probe(net, server, server == fast);
 		first_pass = false;
 		goto again;
 	}

 	write_sequnlock(&net->fs_lock);

 	if (server) {
 		if (!queue_work(afs_wq, &net->fs_prober))
 			afs_dec_servers_outstanding(net);
 		_leave(" [requeue]");
 	} else if (set_timer) {
 		if (timer_reduce(&net->fs_probe_timer, timer_at))
 			afs_dec_servers_outstanding(net);
 		_leave(" [timer]");
 	} else {
 		afs_dec_servers_outstanding(net);
 		_leave(" [quiesce]");
 	}
 }

 /*
  * Wait for a probe on a particular fileserver to complete for 2s.
  */
 int afs_wait_for_one_fs_probe(struct afs_server *server, bool is_intr)
 {
 	struct wait_queue_entry wait;
 	unsigned long timo = 2 * HZ;

 	if (atomic_read(&server->probe_outstanding) == 0)
 		goto dont_wait;

 	init_wait_entry(&wait, 0);
 	for (;;) {
 		prepare_to_wait_event(&server->probe_wq, &wait,
 				      is_intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 		if (timo == 0 ||
 		    server->probe.responded ||
 		    atomic_read(&server->probe_outstanding) == 0 ||
 		    (is_intr && signal_pending(current)))
 			break;
 		timo = schedule_timeout(timo);
 	}

 	finish_wait(&server->probe_wq, &wait);

 dont_wait:
 	if (server->probe.responded)
 		return 0;
 	if (is_intr && signal_pending(current))
 		return -ERESTARTSYS;
 	if (timo == 0)
 		return -ETIME;
 	return -EDESTADDRREQ;
 }

 /*
  * Clean up the probing when the namespace is killed off.
  */
 void afs_fs_probe_cleanup(struct afs_net *net)
 {
 	if (del_timer_sync(&net->fs_probe_timer))
 		afs_dec_servers_outstanding(net);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* AFS fileserver probing
	*
	* Copyright (C) 2018, 2020 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

	#include <linux/sched.h>
	#include <linux/slab.h>
	#include "afs_fs.h"
	#include "internal.h"
	#include "protocol_afs.h"
	#include "protocol_yfs.h"

	static unsigned int afs_fs_probe_fast_poll_interval = 30 * HZ;
	static unsigned int afs_fs_probe_slow_poll_interval = 5 * 60 * HZ;

	/*
	* Start the probe polling timer. We have to supply it with an inc on the
	* outstanding server count.
	*/
	static void afs_schedule_fs_probe(struct afs_net *net,
	struct afs_server *server, bool fast)
	{
	unsigned long atj;

	if (!net->live)
	return;

	atj = server->probed_at;
	atj += fast ? afs_fs_probe_fast_poll_interval : afs_fs_probe_slow_poll_interval;

	afs_inc_servers_outstanding(net);
	if (timer_reduce(&net->fs_probe_timer, atj))
	afs_dec_servers_outstanding(net);
	}

	/*
	* Handle the completion of a set of probes.
	*/
	static void afs_finished_fs_probe(struct afs_net net, struct afs_server server)
	{
	bool responded = server->probe.responded;

	write_seqlock(&net->fs_lock);
	if (responded) {
	list_add_tail(&server->probe_link, &net->fs_probe_slow);
	} else {
	server->rtt = UINT_MAX;
	clear_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
	list_add_tail(&server->probe_link, &net->fs_probe_fast);
	}
	write_sequnlock(&net->fs_lock);

	afs_schedule_fs_probe(net, server, !responded);
	}

	/*
	* Handle the completion of a probe.
	*/
	static void afs_done_one_fs_probe(struct afs_net net, struct afs_server server)
	{
	_enter("");

	if (atomic_dec_and_test(&server->probe_outstanding))
	afs_finished_fs_probe(net, server);

	wake_up_all(&server->probe_wq);
	}

	/*
	* Handle inability to send a probe due to ENOMEM when trying to allocate a
	* call struct.
	*/
	static void afs_fs_probe_not_done(struct afs_net *net,
	struct afs_server *server,
	struct afs_addr_cursor *ac)
	{
	struct afs_addr_list *alist = ac->alist;
	unsigned int index = ac->index;

	_enter("");

	trace_afs_io_error(0, -ENOMEM, afs_io_error_fs_probe_fail);
	spin_lock(&server->probe_lock);

	server->probe.local_failure = true;
	if (server->probe.error == 0)
	server->probe.error = -ENOMEM;

	set_bit(index, &alist->failed);

	spin_unlock(&server->probe_lock);
	return afs_done_one_fs_probe(net, server);
	}

	/*
	* Process the result of probing a fileserver. This is called after successful
	* or failed delivery of an FS.GetCapabilities operation.
	*/
	void afs_fileserver_probe_result(struct afs_call *call)
	{
	struct afs_addr_list *alist = call->alist;
	struct afs_server *server = call->server;
	unsigned int index = call->addr_ix;
	unsigned int rtt_us = 0, cap0;
	int ret = call->error;

	_enter("%pU,%u", &server->uuid, index);

	spin_lock(&server->probe_lock);

	switch (ret) {
	case 0:
	server->probe.error = 0;
	goto responded;
	case -ECONNABORTED:
	if (!server->probe.responded) {
	server->probe.abort_code = call->abort_code;
	server->probe.error = ret;
	}
	goto responded;
	case -ENOMEM:
	case -ENONET:
	clear_bit(index, &alist->responded);
	server->probe.local_failure = true;
	trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_probe_fail);
	goto out;
	case -ECONNRESET: /* Responded, but call expired. */
	case -ERFKILL:
	case -EADDRNOTAVAIL:
	case -ENETUNREACH:
	case -EHOSTUNREACH:
	case -EHOSTDOWN:
	case -ECONNREFUSED:
	case -ETIMEDOUT:
	case -ETIME:
	default:
	clear_bit(index, &alist->responded);
	set_bit(index, &alist->failed);
	if (!server->probe.responded &&
	(server->probe.error == 0 \|\|
	server->probe.error == -ETIMEDOUT \|\|
	server->probe.error == -ETIME))
	server->probe.error = ret;
	trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_probe_fail);
	goto out;
	}

	responded:
	clear_bit(index, &alist->failed);

	if (call->service_id == YFS_FS_SERVICE) {
	server->probe.is_yfs = true;
	set_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
	alist->addrs[index].srx_service = call->service_id;
	} else {
	server->probe.not_yfs = true;
	if (!server->probe.is_yfs) {
	clear_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
	alist->addrs[index].srx_service = call->service_id;
	}
	cap0 = ntohl(call->tmp);
	if (cap0 & AFS3_VICED_CAPABILITY_64BITFILES)
	set_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
	else
	clear_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
	}

	rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us);
	if (rtt_us < server->probe.rtt) {
	server->probe.rtt = rtt_us;
	server->rtt = rtt_us;
	alist->preferred = index;
	}

	smp_wmb(); /* Set rtt before responded. */
	server->probe.responded = true;
	set_bit(index, &alist->responded);
	set_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
	out:
	spin_unlock(&server->probe_lock);

	_debug("probe %pU [%u] %pISpc rtt=%u ret=%d",
	&server->uuid, index, &alist->addrs[index].transport,
	rtt_us, ret);

	return afs_done_one_fs_probe(call->net, server);
	}

	/*
	* Probe one or all of a fileserver's addresses to find out the best route and
	* to query its capabilities.
	*/
	void afs_fs_probe_fileserver(struct afs_net net, struct afs_server server,
	struct key *key, bool all)
	{
	struct afs_addr_cursor ac = {
	.index = 0,
	};

	_enter("%pU", &server->uuid);

	read_lock(&server->fs_lock);
	ac.alist = rcu_dereference_protected(server->addresses,
	lockdep_is_held(&server->fs_lock));
	afs_get_addrlist(ac.alist);
	read_unlock(&server->fs_lock);

	server->probed_at = jiffies;
	atomic_set(&server->probe_outstanding, all ? ac.alist->nr_addrs : 1);
	memset(&server->probe, 0, sizeof(server->probe));
	server->probe.rtt = UINT_MAX;

	ac.index = ac.alist->preferred;
	if (ac.index < 0 \|\| ac.index >= ac.alist->nr_addrs)
	all = true;

	if (all) {
	for (ac.index = 0; ac.index < ac.alist->nr_addrs; ac.index++)
	if (!afs_fs_get_capabilities(net, server, &ac, key))
	afs_fs_probe_not_done(net, server, &ac);
	} else {
	if (!afs_fs_get_capabilities(net, server, &ac, key))
	afs_fs_probe_not_done(net, server, &ac);
	}

	afs_put_addrlist(ac.alist);
	}

	/*
	* Wait for the first as-yet untried fileserver to respond.
	*/
	int afs_wait_for_fs_probes(struct afs_server_list *slist, unsigned long untried)
	{
	struct wait_queue_entry *waits;
	struct afs_server *server;
	unsigned int rtt = UINT_MAX, rtt_s;
	bool have_responders = false;
	int pref = -1, i;

	_enter("%u,%lx", slist->nr_servers, untried);

	/* Only wait for servers that have a probe outstanding. */
	for (i = 0; i < slist->nr_servers; i++) {
	if (test_bit(i, &untried)) {
	server = slist->servers[i].server;
	if (!atomic_read(&server->probe_outstanding))
	__clear_bit(i, &untried);
	if (server->probe.responded)
	have_responders = true;
	}
	}
	if (have_responders \|\| !untried)
	return 0;

	waits = kmalloc(array_size(slist->nr_servers, sizeof(*waits)), GFP_KERNEL);
	if (!waits)
	return -ENOMEM;

	for (i = 0; i < slist->nr_servers; i++) {
	if (test_bit(i, &untried)) {
	server = slist->servers[i].server;
	init_waitqueue_entry(&waits[i], current);
	add_wait_queue(&server->probe_wq, &waits[i]);
	}
	}

	for (;;) {
	bool still_probing = false;

	set_current_state(TASK_INTERRUPTIBLE);
	for (i = 0; i < slist->nr_servers; i++) {
	if (test_bit(i, &untried)) {
	server = slist->servers[i].server;
	if (server->probe.responded)
	goto stop;
	if (atomic_read(&server->probe_outstanding))
	still_probing = true;
	}
	}

	if (!still_probing \|\| signal_pending(current))
	goto stop;
	schedule();
	}

	stop:
	set_current_state(TASK_RUNNING);

	for (i = 0; i < slist->nr_servers; i++) {
	if (test_bit(i, &untried)) {
	server = slist->servers[i].server;
	rtt_s = READ_ONCE(server->rtt);
	if (test_bit(AFS_SERVER_FL_RESPONDING, &server->flags) &&
	rtt_s < rtt) {
	pref = i;
	rtt = rtt_s;
	}

	remove_wait_queue(&server->probe_wq, &waits[i]);
	}
	}

	kfree(waits);

	if (pref == -1 && signal_pending(current))
	return -ERESTARTSYS;

	if (pref >= 0)
	slist->preferred = pref;
	return 0;
	}

	/*
	* Probe timer. We have an increment on fs_outstanding that we need to pass
	* along to the work item.
	*/
	void afs_fs_probe_timer(struct timer_list *timer)
	{
	struct afs_net *net = container_of(timer, struct afs_net, fs_probe_timer);

	if (!net->live \|\| !queue_work(afs_wq, &net->fs_prober))
	afs_dec_servers_outstanding(net);
	}

	/*
	* Dispatch a probe to a server.
	*/
	static void afs_dispatch_fs_probe(struct afs_net net, struct afs_server server, bool all)
	__releases(&net->fs_lock)
	{
	struct key *key = NULL;

	/* We remove it from the queues here - it will be added back to
	* one of the queues on the completion of the probe.
	*/
	list_del_init(&server->probe_link);

	afs_get_server(server, afs_server_trace_get_probe);
	write_sequnlock(&net->fs_lock);

	afs_fs_probe_fileserver(net, server, key, all);
	afs_put_server(net, server, afs_server_trace_put_probe);
	}

	/*
	* Probe a server immediately without waiting for its due time to come
	* round. This is used when all of the addresses have been tried.
	*/
	void afs_probe_fileserver(struct afs_net net, struct afs_server server)
	{
	write_seqlock(&net->fs_lock);
	if (!list_empty(&server->probe_link))
	return afs_dispatch_fs_probe(net, server, true);
	write_sequnlock(&net->fs_lock);
	}

	/*
	* Probe dispatcher to regularly dispatch probes to keep NAT alive.
	*/
	void afs_fs_probe_dispatcher(struct work_struct *work)
	{
	struct afs_net *net = container_of(work, struct afs_net, fs_prober);
	struct afs_server fast, slow, *server;
	unsigned long nowj, timer_at, poll_at;
	bool first_pass = true, set_timer = false;

	if (!net->live) {
	afs_dec_servers_outstanding(net);
	return;
	}

	_enter("");

	if (list_empty(&net->fs_probe_fast) && list_empty(&net->fs_probe_slow)) {
	afs_dec_servers_outstanding(net);
	_leave(" [none]");
	return;
	}

	again:
	write_seqlock(&net->fs_lock);

	fast = slow = server = NULL;
	nowj = jiffies;
	timer_at = nowj + MAX_JIFFY_OFFSET;

	if (!list_empty(&net->fs_probe_fast)) {
	fast = list_first_entry(&net->fs_probe_fast, struct afs_server, probe_link);
	poll_at = fast->probed_at + afs_fs_probe_fast_poll_interval;
	if (time_before(nowj, poll_at)) {
	timer_at = poll_at;
	set_timer = true;
	fast = NULL;
	}
	}

	if (!list_empty(&net->fs_probe_slow)) {
	slow = list_first_entry(&net->fs_probe_slow, struct afs_server, probe_link);
	poll_at = slow->probed_at + afs_fs_probe_slow_poll_interval;
	if (time_before(nowj, poll_at)) {
	if (time_before(poll_at, timer_at))
	timer_at = poll_at;
	set_timer = true;
	slow = NULL;
	}
	}

	server = fast ?: slow;
	if (server)
	_debug("probe %pU", &server->uuid);

	if (server && (first_pass \|\| !need_resched())) {
	afs_dispatch_fs_probe(net, server, server == fast);
	first_pass = false;
	goto again;
	}

	write_sequnlock(&net->fs_lock);

	if (server) {
	if (!queue_work(afs_wq, &net->fs_prober))
	afs_dec_servers_outstanding(net);
	_leave(" [requeue]");
	} else if (set_timer) {
	if (timer_reduce(&net->fs_probe_timer, timer_at))
	afs_dec_servers_outstanding(net);
	_leave(" [timer]");
	} else {
	afs_dec_servers_outstanding(net);
	_leave(" [quiesce]");
	}
	}

	/*
	* Wait for a probe on a particular fileserver to complete for 2s.
	*/
	int afs_wait_for_one_fs_probe(struct afs_server *server, bool is_intr)
	{
	struct wait_queue_entry wait;
	unsigned long timo = 2 * HZ;

	if (atomic_read(&server->probe_outstanding) == 0)
	goto dont_wait;

	init_wait_entry(&wait, 0);
	for (;;) {
	prepare_to_wait_event(&server->probe_wq, &wait,
	is_intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
	if (timo == 0 \|\|
	server->probe.responded \|\|
	atomic_read(&server->probe_outstanding) == 0 \|\|
	(is_intr && signal_pending(current)))
	break;
	timo = schedule_timeout(timo);
	}

	finish_wait(&server->probe_wq, &wait);

	dont_wait:
	if (server->probe.responded)
	return 0;
	if (is_intr && signal_pending(current))
	return -ERESTARTSYS;
	if (timo == 0)
	return -ETIME;
	return -EDESTADDRREQ;
	}

	/*
	* Clean up the probing when the namespace is killed off.
	*/
	void afs_fs_probe_cleanup(struct afs_net *net)
	{
	if (del_timer_sync(&net->fs_probe_timer))
	afs_dec_servers_outstanding(net);
	}