text: // SPDX-License-Identifier: GPL-2.0-or-later
  /* AFS server record management
   *
   * Copyright (C) 2002, 2007 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_yfs.h"
  
  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 atomic_t afs_server_debug_id;
  
  static void afs_inc_servers_outstanding(struct afs_net *net)
  {
  	atomic_inc(&net->servers_outstanding);
  }
  
  static void afs_dec_servers_outstanding(struct afs_net *net)
  {
  	if (atomic_dec_and_test(&net->servers_outstanding))
  		wake_up_var(&net->servers_outstanding);
  }
  
  /*
   * Find a server by one of its addresses.
   */
  struct afs_server *afs_find_server(struct afs_net *net,
  				   const struct sockaddr_rxrpc *srx)
  {
  	const struct afs_addr_list *alist;
  	struct afs_server *server = NULL;
  	unsigned int i;
  	int seq = 0, diff;
  
  	rcu_read_lock();
  
  	do {
  		if (server)
  			afs_put_server(net, server, afs_server_trace_put_find_rsq);
  		server = NULL;
  		read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
  
  		if (srx->transport.family == AF_INET6) {
  			const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
  			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 __force)a->sin6_port -
  						(u16 __force)b->sin6_port);
  					if (diff == 0)
  						diff = memcmp(&a->sin6_addr,
  							      &b->sin6_addr,
  							      sizeof(struct in6_addr));
  					if (diff == 0)
  						goto found;
  				}
  			}
  		} else {
  			const struct sockaddr_in *a = &srx->transport.sin, *b;
  			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.sin;
  					diff = ((u16 __force)a->sin_port -
  						(u16 __force)b->sin_port);
  					if (diff == 0)
  						diff = ((u32 __force)a->sin_addr.s_addr -
  							(u32 __force)b->sin_addr.s_addr);
  					if (diff == 0)
  						goto 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;
  }
  
  /*
   * Look up a server by its UUID
   */
  struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
  {
  	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, afs_server_trace_put_uuid_rsq);
  		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, afs_server_trace_get_by_uuid);
  				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 diff;
  
  	_enter("%p", candidate);
  
  	write_seqlock(&net->fs_lock);
  
  	/* 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);
  		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 exists;
  	}
  
  	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);
  
  exists:
  	afs_get_server(server, afs_server_trace_get_install);
  	write_sequnlock(&net->fs_lock);
  	return server;
  }
  
  /*
   * allocate a new server record
   */
  static struct afs_server *afs_alloc_server(struct afs_net *net,
  					   const uuid_t *uuid,
  					   struct afs_addr_list *alist)
  {
  	struct afs_server *server;
  
  	_enter("");
  
  	server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
  	if (!server)
  		goto enomem;
  
  	atomic_set(&server->usage, 1);
  	server->debug_id = atomic_inc_return(&afs_server_debug_id);
  	RCU_INIT_POINTER(server->addresses, alist);
  	server->addr_version = alist->version;
  	server->uuid = *uuid;
  	server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
  	rwlock_init(&server->fs_lock);
  	INIT_HLIST_HEAD(&server->cb_volumes);
  	rwlock_init(&server->cb_break_lock);
  	init_waitqueue_head(&server->probe_wq);
  	spin_lock_init(&server->probe_lock);
  
  	afs_inc_servers_outstanding(net);
  	trace_afs_server(server, 1, afs_server_trace_alloc);
  	_leave(" = %p", server);
  	return server;
  
  enomem:
  	_leave(" = NULL [nomem]");
  	return NULL;
  }
  
  /*
   * Look up an address record for a server
   */
  static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
  						 struct key *key, const uuid_t *uuid)
  {
  	struct afs_vl_cursor vc;
  	struct afs_addr_list *alist = NULL;
  	int ret;
  
  	ret = -ERESTARTSYS;
  	if (afs_begin_vlserver_operation(&vc, cell, key)) {
  		while (afs_select_vlserver(&vc)) {
  			if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
  				alist = afs_yfsvl_get_endpoints(&vc, uuid);
  			else
  				alist = afs_vl_get_addrs_u(&vc, uuid);
  		}
  
  		ret = afs_end_vlserver_operation(&vc);
  	}
  
  	return ret < 0 ? ERR_PTR(ret) : alist;
  }
  
  /*
   * Get or create a fileserver record.
   */
  struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
  				     const uuid_t *uuid)
  {
  	struct afs_addr_list *alist;
  	struct afs_server *server, *candidate;
  
  	_enter("%p,%pU", cell->net, uuid);
  
  	server = afs_find_server_by_uuid(cell->net, uuid);
  	if (server)
  		return server;
  
  	alist = afs_vl_lookup_addrs(cell, key, uuid);
  	if (IS_ERR(alist))
  		return ERR_CAST(alist);
  
  	candidate = afs_alloc_server(cell->net, uuid, alist);
  	if (!candidate) {
  		afs_put_addrlist(alist);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	server = afs_install_server(cell->net, candidate);
  	if (server != candidate) {
  		afs_put_addrlist(alist);
  		kfree(candidate);
  	}
  
  	_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)
  {
  	if (net->live) {
  		afs_inc_servers_outstanding(net);
  		if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
  			afs_dec_servers_outstanding(net);
  	}
  }
  
  /*
   * 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);
  }
  
  /*
   * Get a reference on a server object.
   */
  struct afs_server *afs_get_server(struct afs_server *server,
  				  enum afs_server_trace reason)
  {
  	unsigned int u = atomic_inc_return(&server->usage);
  
  	trace_afs_server(server, u, reason);
  	return server;
  }
  
  /*
   * Release a reference on a server record.
   */
  void afs_put_server(struct afs_net *net, struct afs_server *server,
  		    enum afs_server_trace reason)
  {
  	unsigned int usage;
  
  	if (!server)
  		return;
  
  	server->put_time = ktime_get_real_seconds();
  
  	usage = atomic_dec_return(&server->usage);
  
  	trace_afs_server(server, usage, reason);
  
  	if (likely(usage > 0))
  		return;
  
  	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);
  
  	trace_afs_server(server, atomic_read(&server->usage),
  			 afs_server_trace_free);
  	afs_put_addrlist(rcu_access_pointer(server->addresses));
  	kfree(server);
  }
  
  /*
   * destroy a dead server
   */
  static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
  {
  	struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
  	struct afs_addr_cursor ac = {
  		.alist	= alist,
  		.index	= alist->preferred,
  		.error	= 0,
  	};
  
  	trace_afs_server(server, atomic_read(&server->usage),
  			 afs_server_trace_give_up_cb);
  
  	if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
  		afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
  
  	wait_var_event(&server->probe_outstanding,
  		       atomic_read(&server->probe_outstanding) == 0);
  
  	trace_afs_server(server, atomic_read(&server->usage),
  			 afs_server_trace_destroy);
  	call_rcu(&server->rcu, afs_server_rcu);
  	afs_dec_servers_outstanding(net);
  }
  
  /*
   * Garbage collect any expired servers.
   */
  static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
  {
  	struct afs_server *server;
  	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);
  		trace_afs_server(server, usage, afs_server_trace_gc);
  		if (deleted) {
  			rb_erase(&server->uuid_rb, &net->fs_servers);
  			hlist_del_rcu(&server->proc_link);
  		}
  		write_sequnlock(&net->fs_lock);
  
  		if (deleted) {
  			write_seqlock(&net->fs_addr_lock);
  			if (!hlist_unhashed(&server->addr4_link))
  				hlist_del_rcu(&server->addr4_link);
  			if (!hlist_unhashed(&server->addr6_link))
  				hlist_del_rcu(&server->addr6_link);
  			write_sequnlock(&net->fs_addr_lock);
  			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;
  			}
  		}
  	}
  
  	read_sequnlock_excl(&net->fs_lock);
  
  	/* 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);
  }
  
  /*
   * Purge list of servers.
   */
  void afs_purge_servers(struct afs_net *net)
  {
  	_enter("");
  
  	if (del_timer_sync(&net->fs_timer))
  		atomic_dec(&net->servers_outstanding);
  
  	afs_queue_server_manager(net);
  
  	_debug("wait");
  	wait_var_event(&net->servers_outstanding,
  		       !atomic_read(&net->servers_outstanding));
  	_leave("");
  }
  
  /*
   * 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("");
  
  	trace_afs_server(server, atomic_read(&server->usage), afs_server_trace_update);
  
  	alist = afs_vl_lookup_addrs(fc->vnode->volume->cell, fc->key,
  				    &server->uuid);
  	if (IS_ERR(alist)) {
  		if ((PTR_ERR(alist) == -ERESTARTSYS ||
  		     PTR_ERR(alist) == -EINTR) &&
  		    !(fc->flags & AFS_FS_CURSOR_INTR) &&
  		    server->addresses) {
  			_leave(" = t [intr]");
  			return true;
  		}
  		fc->error = PTR_ERR(alist);
  		_leave(" = f [%d]", fc->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) {
  		if (!(fc->flags & AFS_FS_CURSOR_INTR) && server->addresses) {
  			_leave(" = t [intr]");
  			return true;
  		}
  		fc->error = ret;
  		_leave(" = f [intr]");
  		return false;
  	}
  
  	retries++;
  	if (retries == 4) {
  		_leave(" = f [stale]");
  		ret = -ESTALE;
  		return false;
  	}
  	goto retry;
  }
  