1 files changed, 537 insertions, 213 deletions

diff --git a/fs/afs/server.c b/fs/afs/server.c
index 9ca174b24f5b..a6c860bcf391 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -14,7 +14,8 @@
 #include "afs_fs.h"
 #include "internal.h"
 
-static unsigned afs_server_timeout = 10;	/* server timeout in seconds */
+static unsigned afs_server_gc_delay = 10;	/* Server record timeout in seconds */
+static unsigned afs_server_update_delay = 30;	/* Time till VLDB recheck in secs */
 
 static void afs_inc_servers_outstanding(struct afs_net *net)
 {
@@ -27,60 +28,201 @@ static void afs_dec_servers_outstanding(struct afs_net *net)
 		wake_up_atomic_t(&net->servers_outstanding);
 }
 
-void afs_server_timer(struct timer_list *timer)
+/*
+ * Find a server by one of its addresses.
+ */
+struct afs_server *afs_find_server(struct afs_net *net,
+				   const struct sockaddr_rxrpc *srx)
 {
-	struct afs_net *net = container_of(timer, struct afs_net, server_timer);
+	const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
+	const struct afs_addr_list *alist;
+	struct afs_server *server = NULL;
+	unsigned int i;
+	bool ipv6 = true;
+	int seq = 0, diff;
+
+	if (srx->transport.sin6.sin6_addr.s6_addr32[0] == 0 ||
+	    srx->transport.sin6.sin6_addr.s6_addr32[1] == 0 ||
+	    srx->transport.sin6.sin6_addr.s6_addr32[2] == htonl(0xffff))
+		ipv6 = false;
+
+	rcu_read_lock();
+
+	do {
+		if (server)
+			afs_put_server(net, server);
+		server = NULL;
+		read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
+
+		if (ipv6) {
+			hlist_for_each_entry_rcu(server, &net->fs_addresses6, addr6_link) {
+				alist = rcu_dereference(server->addresses);
+				for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
+					b = &alist->addrs[i].transport.sin6;
+					diff = (u16)a->sin6_port - (u16)b->sin6_port;
+					if (diff == 0)
+						diff = memcmp(&a->sin6_addr,
+							      &b->sin6_addr,
+							      sizeof(struct in6_addr));
+					if (diff == 0)
+						goto found;
+					if (diff < 0) {
+						// TODO: Sort the list
+						//if (i == alist->nr_ipv4)
+						//	goto not_found;
+						break;
+					}
+				}
+			}
+		} else {
+			hlist_for_each_entry_rcu(server, &net->fs_addresses4, addr4_link) {
+				alist = rcu_dereference(server->addresses);
+				for (i = 0; i < alist->nr_ipv4; i++) {
+					b = &alist->addrs[i].transport.sin6;
+					diff = (u16)a->sin6_port - (u16)b->sin6_port;
+					if (diff == 0)
+						diff = ((u32)a->sin6_addr.s6_addr32[3] -
+							(u32)b->sin6_addr.s6_addr32[3]);
+					if (diff == 0)
+						goto found;
+					if (diff < 0) {
+						// TODO: Sort the list
+						//if (i == 0)
+						//	goto not_found;
+						break;
+					}
+				}
+			}
+		}
 
-	if (!queue_work(afs_wq, &net->server_reaper))
-		afs_dec_servers_outstanding(net);
+	//not_found:
+		server = NULL;
+	found:
+		if (server && !atomic_inc_not_zero(&server->usage))
+			server = NULL;
+
+	} while (need_seqretry(&net->fs_addr_lock, seq));
+
+	done_seqretry(&net->fs_addr_lock, seq);
+
+	rcu_read_unlock();
+	return server;
 }
 
 /*
- * install a server record in the master tree
+ * Look up a server by its UUID
  */
-static int afs_install_server(struct afs_server *server)
+struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
 {
-	struct afs_server *xserver;
-	struct afs_net *net = server->cell->net;
+	struct afs_server *server = NULL;
+	struct rb_node *p;
+	int diff, seq = 0;
+
+	_enter("%pU", uuid);
+
+	do {
+		/* Unfortunately, rbtree walking doesn't give reliable results
+		 * under just the RCU read lock, so we have to check for
+		 * changes.
+		 */
+		if (server)
+			afs_put_server(net, server);
+		server = NULL;
+
+		read_seqbegin_or_lock(&net->fs_lock, &seq);
+
+		p = net->fs_servers.rb_node;
+		while (p) {
+			server = rb_entry(p, struct afs_server, uuid_rb);
+
+			diff = memcmp(uuid, &server->uuid, sizeof(*uuid));
+			if (diff < 0) {
+				p = p->rb_left;
+			} else if (diff > 0) {
+				p = p->rb_right;
+			} else {
+				afs_get_server(server);
+				break;
+			}
+
+			server = NULL;
+		}
+	} while (need_seqretry(&net->fs_lock, seq));
+
+	done_seqretry(&net->fs_lock, seq);
+
+	_leave(" = %p", server);
+	return server;
+}
+
+/*
+ * Install a server record in the namespace tree
+ */
+static struct afs_server *afs_install_server(struct afs_net *net,
+					     struct afs_server *candidate)
+{
+	const struct afs_addr_list *alist;
+	struct afs_server *server;
 	struct rb_node **pp, *p;
-	int ret, diff;
+	int ret = -EEXIST, diff;
 
-	_enter("%p", server);
+	_enter("%p", candidate);
 
-	write_lock(&net->servers_lock);
+	write_seqlock(&net->fs_lock);
 
-	ret = -EEXIST;
-	pp = &net->servers.rb_node;
+	/* Firstly install the server in the UUID lookup tree */
+	pp = &net->fs_servers.rb_node;
 	p = NULL;
 	while (*pp) {
 		p = *pp;
 		_debug("- consider %p", p);
-		xserver = rb_entry(p, struct afs_server, master_rb);
-		diff = memcmp(&server->addrs->addrs[0],
-			      &xserver->addrs->addrs[0],
-			      sizeof(sizeof(server->addrs->addrs[0])));
+		server = rb_entry(p, struct afs_server, uuid_rb);
+		diff = memcmp(&candidate->uuid, &server->uuid, sizeof(uuid_t));
 		if (diff < 0)
 			pp = &(*pp)->rb_left;
 		else if (diff > 0)
 			pp = &(*pp)->rb_right;
 		else
-			goto error;
+			goto exists;
 	}
 
-	rb_link_node(&server->master_rb, p, pp);
-	rb_insert_color(&server->master_rb, &net->servers);
+	server = candidate;
+	rb_link_node(&server->uuid_rb, p, pp);
+	rb_insert_color(&server->uuid_rb, &net->fs_servers);
+	hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
+
+	write_seqlock(&net->fs_addr_lock);
+	alist = rcu_dereference_protected(server->addresses,
+					  lockdep_is_held(&net->fs_addr_lock.lock));
+
+	/* Secondly, if the server has any IPv4 and/or IPv6 addresses, install
+	 * it in the IPv4 and/or IPv6 reverse-map lists.
+	 *
+	 * TODO: For speed we want to use something other than a flat list
+	 * here; even sorting the list in terms of lowest address would help a
+	 * bit, but anything we might want to do gets messy and memory
+	 * intensive.
+	 */
+	if (alist->nr_ipv4 > 0)
+		hlist_add_head_rcu(&server->addr4_link, &net->fs_addresses4);
+	if (alist->nr_addrs > alist->nr_ipv4)
+		hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);
+
+	write_sequnlock(&net->fs_addr_lock);
 	ret = 0;
 
-error:
-	write_unlock(&net->servers_lock);
-	return ret;
+exists:
+	afs_get_server(server);
+	write_sequnlock(&net->fs_lock);
+	return server;
 }
 
 /*
  * allocate a new server record
  */
-static struct afs_server *afs_alloc_server(struct afs_cell *cell,
-					   const struct sockaddr_rxrpc *addr)
+static struct afs_server *afs_alloc_server(struct afs_net *net,
+					   const uuid_t *uuid,
+					   struct afs_addr_list *alist)
 {
 	struct afs_server *server;
 
@@ -89,194 +231,155 @@ static struct afs_server *afs_alloc_server(struct afs_cell *cell,
 	server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
 	if (!server)
 		goto enomem;
-	server->addrs = kzalloc(sizeof(struct afs_addr_list) +
-				sizeof(struct sockaddr_rxrpc),
-				GFP_KERNEL);
-	if (!server->addrs)
-		goto enomem_server;
 
 	atomic_set(&server->usage, 1);
-	server->net = cell->net;
-	server->cell = cell;
-
-	INIT_LIST_HEAD(&server->link);
-	INIT_LIST_HEAD(&server->grave);
-	init_rwsem(&server->sem);
-	spin_lock_init(&server->fs_lock);
+	RCU_INIT_POINTER(server->addresses, alist);
+	server->addr_version = alist->version;
+	server->uuid = *uuid;
+	server->flags = (1UL << AFS_SERVER_FL_NEW);
+	server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
+	rwlock_init(&server->fs_lock);
 	INIT_LIST_HEAD(&server->cb_interests);
 	rwlock_init(&server->cb_break_lock);
 
-	refcount_set(&server->addrs->usage, 1);
-	server->addrs->nr_addrs = 1;
-	server->addrs->addrs[0] = *addr;
-	afs_inc_servers_outstanding(cell->net);
-
-	_leave(" = %p{%d}", server, atomic_read(&server->usage));
+	afs_inc_servers_outstanding(net);
+	_leave(" = %p", server);
 	return server;
 
-enomem_server:
-	kfree(server);
 enomem:
 	_leave(" = NULL [nomem]");
 	return NULL;
 }
 
 /*
- * get an FS-server record for a cell
+ * Look up an address record for a server
  */
-struct afs_server *afs_lookup_server(struct afs_cell *cell,
-				     struct sockaddr_rxrpc *addr)
+static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
+						 struct key *key, const uuid_t *uuid)
 {
-	struct afs_server *server, *candidate;
-
-	_enter("%p,%pIS", cell, &addr->transport);
-
-	/* quick scan of the list to see if we already have the server */
-	read_lock(&cell->servers_lock);
-
-	list_for_each_entry(server, &cell->servers, link) {
-		if (memcmp(&server->addrs->addrs[0], addr, sizeof(*addr)) == 0)
-			goto found_server_quickly;
-	}
-	read_unlock(&cell->servers_lock);
-
-	candidate = afs_alloc_server(cell, addr);
-	if (!candidate) {
-		_leave(" = -ENOMEM");
-		return ERR_PTR(-ENOMEM);
-	}
-
-	write_lock(&cell->servers_lock);
-
-	/* check the cell's server list again */
-	list_for_each_entry(server, &cell->servers, link) {
-		if (memcmp(&server->addrs->addrs[0], addr, sizeof(*addr)) == 0)
-			goto found_server;
-	}
-
-	_debug("new");
-	server = candidate;
-	if (afs_install_server(server) < 0)
-		goto server_in_two_cells;
-
-	afs_get_cell(cell);
-	list_add_tail(&server->link, &cell->servers);
-
-	write_unlock(&cell->servers_lock);
-	_leave(" = %p{%d}", server, atomic_read(&server->usage));
-	return server;
-
-	/* found a matching server quickly */
-found_server_quickly:
-	_debug("found quickly");
-	afs_get_server(server);
-	read_unlock(&cell->servers_lock);
-no_longer_unused:
-	if (!list_empty(&server->grave)) {
-		spin_lock(&cell->net->server_graveyard_lock);
-		list_del_init(&server->grave);
-		spin_unlock(&cell->net->server_graveyard_lock);
+	struct afs_addr_cursor ac;
+	struct afs_addr_list *alist;
+	int ret;
+
+	ret = afs_set_vl_cursor(&ac, cell);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	while (afs_iterate_addresses(&ac)) {
+		alist = afs_vl_get_addrs_u(cell->net, &ac, key, uuid);
+		switch (ac.error) {
+		case 0:
+			afs_end_cursor(&ac);
+			return alist;
+		case -ECONNABORTED:
+			ac.error = afs_abort_to_error(ac.abort_code);
+			goto error;
+		case -ENOMEM:
+		case -ENONET:
+			goto error;
+		case -ENETUNREACH:
+		case -EHOSTUNREACH:
+		case -ECONNREFUSED:
+			break;
+		default:
+			ac.error = -EIO;
+			goto error;
+		}
 	}
-	_leave(" = %p{%d}", server, atomic_read(&server->usage));
-	return server;
 
-	/* found a matching server on the second pass */
-found_server:
-	_debug("found");
-	afs_get_server(server);
-	write_unlock(&cell->servers_lock);
-	kfree(candidate);
-	goto no_longer_unused;
-
-	/* found a server that seems to be in two cells */
-server_in_two_cells:
-	write_unlock(&cell->servers_lock);
-	kfree(candidate);
-	afs_dec_servers_outstanding(cell->net);
-	printk(KERN_NOTICE "kAFS: Server %pI4 appears to be in two cells\n",
-	       addr);
-	_leave(" = -EEXIST");
-	return ERR_PTR(-EEXIST);
+error:
+	return ERR_PTR(afs_end_cursor(&ac));
 }
 
 /*
- * look up a server by its IP address
+ * Get or create a fileserver record.
  */
-struct afs_server *afs_find_server(struct afs_net *net,
-				   const struct sockaddr_rxrpc *srx)
+struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
+				     const uuid_t *uuid)
 {
-	struct afs_server *server = NULL;
-	struct rb_node *p;
-	int diff;
+	struct afs_addr_list *alist;
+	struct afs_server *server, *candidate;
 
-	_enter("{%d,%pIS}", srx->transport.family, &srx->transport);
+	_enter("%p,%pU", cell->net, uuid);
 
-	read_lock(&net->servers_lock);
+	server = afs_find_server_by_uuid(cell->net, uuid);
+	if (server)
+		return server;
 
-	p = net->servers.rb_node;
-	while (p) {
-		server = rb_entry(p, struct afs_server, master_rb);
+	alist = afs_vl_lookup_addrs(cell, key, uuid);
+	if (IS_ERR(alist))
+		return ERR_CAST(alist);
 
-		_debug("- consider %p", p);
+	candidate = afs_alloc_server(cell->net, uuid, alist);
+	if (!candidate) {
+		afs_put_addrlist(alist);
+		return ERR_PTR(-ENOMEM);
+	}
 
-		diff = memcmp(srx, &server->addrs->addrs[0], sizeof(*srx));
-		if (diff < 0) {
-			p = p->rb_left;
-		} else if (diff > 0) {
-			p = p->rb_right;
-		} else {
-			afs_get_server(server);
-			goto found;
-		}
+	server = afs_install_server(cell->net, candidate);
+	if (server != candidate) {
+		afs_put_addrlist(alist);
+		kfree(candidate);
 	}
 
-	server = NULL;
-found:
-	read_unlock(&net->servers_lock);
-	_leave(" = %p", server);
+	_leave(" = %p{%d}", server, atomic_read(&server->usage));
 	return server;
 }
 
+/*
+ * Set the server timer to fire after a given delay, assuming it's not already
+ * set for an earlier time.
+ */
 static void afs_set_server_timer(struct afs_net *net, time64_t delay)
 {
-	afs_inc_servers_outstanding(net);
 	if (net->live) {
-		if (timer_reduce(&net->server_timer, jiffies + delay * HZ))
-			afs_dec_servers_outstanding(net);
-	} else {
-		if (!queue_work(afs_wq, &net->server_reaper))
+		afs_inc_servers_outstanding(net);
+		if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
 			afs_dec_servers_outstanding(net);
 	}
 }
 
 /*
- * destroy a server record
- * - removes from the cell list
+ * Server management timer.  We have an increment on fs_outstanding that we
+ * need to pass along to the work item.
+ */
+void afs_servers_timer(struct timer_list *timer)
+{
+	struct afs_net *net = container_of(timer, struct afs_net, fs_timer);
+
+	_enter("");
+	if (!queue_work(afs_wq, &net->fs_manager))
+		afs_dec_servers_outstanding(net);
+}
+
+/*
+ * Release a reference on a server record.
  */
 void afs_put_server(struct afs_net *net, struct afs_server *server)
 {
+	unsigned int usage;
+
 	if (!server)
 		return;
 
-	_enter("%p{%d}", server, atomic_read(&server->usage));
+	server->put_time = ktime_get_real_seconds();
 
-	_debug("PUT SERVER %d", atomic_read(&server->usage));
+	usage = atomic_dec_return(&server->usage);
 
-	ASSERTCMP(atomic_read(&server->usage), >, 0);
+	_enter("{%u}", usage);
 
-	if (likely(!atomic_dec_and_test(&server->usage))) {
-		_leave("");
+	if (likely(usage > 0))
 		return;
-	}
 
-	spin_lock(&net->server_graveyard_lock);
-	if (atomic_read(&server->usage) == 0) {
-		list_move_tail(&server->grave, &net->server_graveyard);
-		server->time_of_death = ktime_get_real_seconds();
-		afs_set_server_timer(net, afs_server_timeout);
-	}
-	spin_unlock(&net->server_graveyard_lock);
-	_leave(" [dead]");
+	afs_set_server_timer(net, afs_server_gc_delay);
+}
+
+static void afs_server_rcu(struct rcu_head *rcu)
+{
+	struct afs_server *server = container_of(rcu, struct afs_server, rcu);
+
+	afs_put_addrlist(server->addresses);
+	kfree(server);
 }
 
 /*
@@ -284,7 +387,7 @@ void afs_put_server(struct afs_net *net, struct afs_server *server)
  */
 static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 {
-	struct afs_addr_list *alist = server->addrs;
+	struct afs_addr_list *alist = server->addresses;
 	struct afs_addr_cursor ac = {
 		.alist	= alist,
 		.addr	= &alist->addrs[0],
@@ -294,79 +397,300 @@ static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 	};
 	_enter("%p", server);
 
-	afs_fs_give_up_all_callbacks(server, &ac, NULL, false);
-	afs_put_cell(net, server->cell);
-	afs_put_addrlist(server->addrs);
-	kfree(server);
+	afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
+	call_rcu(&server->rcu, afs_server_rcu);
 	afs_dec_servers_outstanding(net);
 }
 
 /*
- * reap dead server records
+ * Garbage collect any expired servers.
  */
-void afs_reap_server(struct work_struct *work)
+static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 {
-	LIST_HEAD(corpses);
 	struct afs_server *server;
-	struct afs_net *net = container_of(work, struct afs_net, server_reaper);
-	unsigned long delay, expiry;
-	time64_t now;
-
-	now = ktime_get_real_seconds();
-	spin_lock(&net->server_graveyard_lock);
-
-	while (!list_empty(&net->server_graveyard)) {
-		server = list_entry(net->server_graveyard.next,
-				    struct afs_server, grave);
-
-		/* the queue is ordered most dead first */
-		if (net->live) {
-			expiry = server->time_of_death + afs_server_timeout;
-			if (expiry > now) {
-				delay = (expiry - now);
-				afs_set_server_timer(net, delay);
-				break;
-			}
+	bool deleted;
+	int usage;
+
+	while ((server = gc_list)) {
+		gc_list = server->gc_next;
+
+		write_seqlock(&net->fs_lock);
+		usage = 1;
+		deleted = atomic_try_cmpxchg(&server->usage, &usage, 0);
+		if (deleted) {
+			rb_erase(&server->uuid_rb, &net->fs_servers);
+			hlist_del_rcu(&server->proc_link);
 		}
+		write_sequnlock(&net->fs_lock);
 
-		write_lock(&server->cell->servers_lock);
-		write_lock(&net->servers_lock);
-		if (atomic_read(&server->usage) > 0) {
-			list_del_init(&server->grave);
-		} else {
-			list_move_tail(&server->grave, &corpses);
-			list_del_init(&server->link);
-			rb_erase(&server->master_rb, &net->servers);
+		if (deleted)
+			afs_destroy_server(net, server);
+	}
+}
+
+/*
+ * Manage the records of servers known to be within a network namespace.  This
+ * includes garbage collecting unused servers.
+ *
+ * Note also that we were given an increment on net->servers_outstanding by
+ * whoever queued us that we need to deal with before returning.
+ */
+void afs_manage_servers(struct work_struct *work)
+{
+	struct afs_net *net = container_of(work, struct afs_net, fs_manager);
+	struct afs_server *gc_list = NULL;
+	struct rb_node *cursor;
+	time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
+	bool purging = !net->live;
+
+	_enter("");
+
+	/* Trawl the server list looking for servers that have expired from
+	 * lack of use.
+	 */
+	read_seqlock_excl(&net->fs_lock);
+
+	for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
+		struct afs_server *server =
+			rb_entry(cursor, struct afs_server, uuid_rb);
+		int usage = atomic_read(&server->usage);
+
+		_debug("manage %pU %u", &server->uuid, usage);
+
+		ASSERTCMP(usage, >=, 1);
+		ASSERTIFCMP(purging, usage, ==, 1);
+
+		if (usage == 1) {
+			time64_t expire_at = server->put_time;
+
+			if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
+			    !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
+				expire_at += afs_server_gc_delay;
+			if (purging || expire_at <= now) {
+				server->gc_next = gc_list;
+				gc_list = server;
+			} else if (expire_at < next_manage) {
+				next_manage = expire_at;
+			}
 		}
-		write_unlock(&net->servers_lock);
-		write_unlock(&server->cell->servers_lock);
 	}
 
-	spin_unlock(&net->server_graveyard_lock);
+	read_sequnlock_excl(&net->fs_lock);
 
-	/* now reap the corpses we've extracted */
-	while (!list_empty(&corpses)) {
-		server = list_entry(corpses.next, struct afs_server, grave);
-		list_del(&server->grave);
-		afs_destroy_server(net, server);
+	/* Update the timer on the way out.  We have to pass an increment on
+	 * servers_outstanding in the namespace that we are in to the timer or
+	 * the work scheduler.
+	 */
+	if (!purging && next_manage < TIME64_MAX) {
+		now = ktime_get_real_seconds();
+
+		if (next_manage - now <= 0) {
+			if (queue_work(afs_wq, &net->fs_manager))
+				afs_inc_servers_outstanding(net);
+		} else {
+			afs_set_server_timer(net, next_manage - now);
+		}
 	}
 
+	afs_gc_servers(net, gc_list);
+
 	afs_dec_servers_outstanding(net);
+	_leave(" [%d]", atomic_read(&net->servers_outstanding));
+}
+
+static void afs_queue_server_manager(struct afs_net *net)
+{
+	afs_inc_servers_outstanding(net);
+	if (!queue_work(afs_wq, &net->fs_manager))
+		afs_dec_servers_outstanding(net);
 }
 
 /*
- * Discard all the server records from a net namespace when it is destroyed or
- * the afs module is removed.
+ * Purge list of servers.
  */
-void __net_exit afs_purge_servers(struct afs_net *net)
+void afs_purge_servers(struct afs_net *net)
 {
-	if (del_timer_sync(&net->server_timer))
+	_enter("");
+
+	if (del_timer_sync(&net->fs_timer))
 		atomic_dec(&net->servers_outstanding);
 
-	afs_inc_servers_outstanding(net);
-	if (!queue_work(afs_wq, &net->server_reaper))
-		afs_dec_servers_outstanding(net);
+	afs_queue_server_manager(net);
 
+	_debug("wait");
 	wait_on_atomic_t(&net->servers_outstanding, atomic_t_wait,
 			 TASK_UNINTERRUPTIBLE);
+	_leave("");
+}
+
+/*
+ * Probe a fileserver to find its capabilities.
+ *
+ * TODO: Try service upgrade.
+ */
+static bool afs_do_probe_fileserver(struct afs_fs_cursor *fc)
+{
+	_enter("");
+
+	fc->ac.addr = NULL;
+	fc->ac.start = READ_ONCE(fc->ac.alist->index);
+	fc->ac.index = fc->ac.start;
+	fc->ac.error = 0;
+	fc->ac.begun = false;
+
+	while (afs_iterate_addresses(&fc->ac)) {
+		afs_fs_get_capabilities(afs_v2net(fc->vnode), fc->cbi->server,
+					&fc->ac, fc->key);
+		switch (fc->ac.error) {
+		case 0:
+			afs_end_cursor(&fc->ac);
+			set_bit(AFS_SERVER_FL_PROBED, &fc->cbi->server->flags);
+			return true;
+		case -ECONNABORTED:
+			fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
+			goto error;
+		case -ENOMEM:
+		case -ENONET:
+			goto error;
+		case -ENETUNREACH:
+		case -EHOSTUNREACH:
+		case -ECONNREFUSED:
+		case -ETIMEDOUT:
+		case -ETIME:
+			break;
+		default:
+			fc->ac.error = -EIO;
+			goto error;
+		}
+	}
+
+error:
+	afs_end_cursor(&fc->ac);
+	return false;
+}
+
+/*
+ * If we haven't already, try probing the fileserver to get its capabilities.
+ * We try not to instigate parallel probes, but it's possible that the parallel
+ * probes will fail due to authentication failure when ours would succeed.
+ *
+ * TODO: Try sending an anonymous probe if an authenticated probe fails.
+ */
+bool afs_probe_fileserver(struct afs_fs_cursor *fc)
+{
+	bool success;
+	int ret, retries = 0;
+
+	_enter("");
+
+retry:
+	if (test_bit(AFS_SERVER_FL_PROBED, &fc->cbi->server->flags)) {
+		_leave(" = t");
+		return true;
+	}
+
+	if (!test_and_set_bit_lock(AFS_SERVER_FL_PROBING, &fc->cbi->server->flags)) {
+		success = afs_do_probe_fileserver(fc);
+		clear_bit_unlock(AFS_SERVER_FL_PROBING, &fc->cbi->server->flags);
+		wake_up_bit(&fc->cbi->server->flags, AFS_SERVER_FL_PROBING);
+		_leave(" = t");
+		return success;
+	}
+
+	_debug("wait");
+	ret = wait_on_bit(&fc->cbi->server->flags, AFS_SERVER_FL_PROBING,
+			  TASK_INTERRUPTIBLE);
+	if (ret == -ERESTARTSYS) {
+		fc->ac.error = ret;
+		_leave(" = f [%d]", ret);
+		return false;
+	}
+
+	retries++;
+	if (retries == 4) {
+		fc->ac.error = -ESTALE;
+		_leave(" = f [stale]");
+		return false;
+	}
+	_debug("retry");
+	goto retry;
+}
+
+/*
+ * Get an update for a server's address list.
+ */
+static noinline bool afs_update_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
+{
+	struct afs_addr_list *alist, *discard;
+
+	_enter("");
+
+	alist = afs_vl_lookup_addrs(fc->vnode->volume->cell, fc->key,
+				    &server->uuid);
+	if (IS_ERR(alist)) {
+		fc->ac.error = PTR_ERR(alist);
+		_leave(" = f [%d]", fc->ac.error);
+		return false;
+	}
+
+	discard = alist;
+	if (server->addr_version != alist->version) {
+		write_lock(&server->fs_lock);
+		discard = rcu_dereference_protected(server->addresses,
+						    lockdep_is_held(&server->fs_lock));
+		rcu_assign_pointer(server->addresses, alist);
+		server->addr_version = alist->version;
+		write_unlock(&server->fs_lock);
+	}
+
+	server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
+	afs_put_addrlist(discard);
+	_leave(" = t");
+	return true;
+}
+
+/*
+ * See if a server's address list needs updating.
+ */
+bool afs_check_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
+{
+	time64_t now = ktime_get_real_seconds();
+	long diff;
+	bool success;
+	int ret, retries = 0;
+
+	_enter("");
+
+	ASSERT(server);
+
+retry:
+	diff = READ_ONCE(server->update_at) - now;
+	if (diff > 0) {
+		_leave(" = t [not now %ld]", diff);
+		return true;
+	}
+
+	if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
+		success = afs_update_server_record(fc, server);
+		clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
+		wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
+		_leave(" = %d", success);
+		return success;
+	}
+
+	ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
+			  TASK_INTERRUPTIBLE);
+	if (ret == -ERESTARTSYS) {
+		fc->ac.error = ret;
+		_leave(" = f [intr]");
+		return false;
+	}
+
+	retries++;
+	if (retries == 4) {
+		_leave(" = f [stale]");
+		ret = -ESTALE;
+		return false;
+	}
+	goto retry;
 }