// SPDX-License-Identifier: GPL-2.0-or-later

  /* Handle vlserver selection and rotation.
   *
   * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */
  
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/sched/signal.h>
  #include "internal.h"
  #include "afs_vl.h"
  
  /*
   * Begin an operation on a volume location server.
   */
  bool afs_begin_vlserver_operation(struct afs_vl_cursor *vc, struct afs_cell *cell,
  				  struct key *key)
  {
  	memset(vc, 0, sizeof(*vc));
  	vc->cell = cell;
  	vc->key = key;
  	vc->error = -EDESTADDRREQ;
  	vc->ac.error = SHRT_MAX;
  
  	if (signal_pending(current)) {
  		vc->error = -EINTR;
  		vc->flags |= AFS_VL_CURSOR_STOP;
  		return false;
  	}
  
  	return true;
  }
  
  /*
   * Begin iteration through a server list, starting with the last used server if
   * possible, or the last recorded good server if not.
   */
  static bool afs_start_vl_iteration(struct afs_vl_cursor *vc)
  {
  	struct afs_cell *cell = vc->cell;

  	unsigned int dns_lookup_count;

  	if (cell->dns_source == DNS_RECORD_UNAVAILABLE ||
  	    cell->dns_expiry <= ktime_get_real_seconds()) {
  		dns_lookup_count = smp_load_acquire(&cell->dns_lookup_count);
  		set_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags);

  		afs_queue_cell(cell, afs_cell_trace_get_queue_dns);

  
  		if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
  			if (wait_var_event_interruptible(
  				    &cell->dns_lookup_count,
  				    smp_load_acquire(&cell->dns_lookup_count)
  				    != dns_lookup_count) < 0) {
  				vc->error = -ERESTARTSYS;
  				return false;
  			}
  		}
  
  		/* Status load is ordered after lookup counter load */
  		if (cell->dns_source == DNS_RECORD_UNAVAILABLE) {
  			vc->error = -EDESTADDRREQ;
  			return false;
  		}

  	}
  
  	read_lock(&cell->vl_servers_lock);
  	vc->server_list = afs_get_vlserverlist(
  		rcu_dereference_protected(cell->vl_servers,
  					  lockdep_is_held(&cell->vl_servers_lock)));
  	read_unlock(&cell->vl_servers_lock);

  	if (!vc->server_list->nr_servers)

  		return false;

  	vc->untried = (1UL << vc->server_list->nr_servers) - 1;
  	vc->index = -1;

  	return true;
  }
  
  /*
   * Select the vlserver to use.  May be called multiple times to rotate
   * through the vlservers.
   */
  bool afs_select_vlserver(struct afs_vl_cursor *vc)
  {
  	struct afs_addr_list *alist;
  	struct afs_vlserver *vlserver;

  	struct afs_error e;

  	u32 rtt;

  	int error = vc->ac.error, i;

  	_enter("%lx[%d],%lx[%d],%d,%d",
  	       vc->untried, vc->index,
  	       vc->ac.tried, vc->ac.index,

  	       error, vc->ac.abort_code);
  
  	if (vc->flags & AFS_VL_CURSOR_STOP) {
  		_leave(" = f [stopped]");
  		return false;
  	}

  	vc->nr_iterations++;

  	/* Evaluate the result of the previous operation, if there was one. */
  	switch (error) {
  	case SHRT_MAX:
  		goto start;
  
  	default:
  	case 0:
  		/* Success or local failure.  Stop. */
  		vc->error = error;
  		vc->flags |= AFS_VL_CURSOR_STOP;
  		_leave(" = f [okay/local %d]", vc->ac.error);
  		return false;
  
  	case -ECONNABORTED:
  		/* The far side rejected the operation on some grounds.  This
  		 * might involve the server being busy or the volume having been moved.
  		 */
  		switch (vc->ac.abort_code) {
  		case AFSVL_IO:
  		case AFSVL_BADVOLOPER:
  		case AFSVL_NOMEM:
  			/* The server went weird. */
  			vc->error = -EREMOTEIO;
  			//write_lock(&vc->cell->vl_servers_lock);
  			//vc->server_list->weird_mask |= 1 << vc->index;
  			//write_unlock(&vc->cell->vl_servers_lock);
  			goto next_server;
  
  		default:
  			vc->error = afs_abort_to_error(vc->ac.abort_code);
  			goto failed;
  		}

  	case -ERFKILL:
  	case -EADDRNOTAVAIL:

  	case -ENETUNREACH:
  	case -EHOSTUNREACH:

  	case -EHOSTDOWN:

  	case -ECONNREFUSED:
  	case -ETIMEDOUT:
  	case -ETIME:
  		_debug("no conn %d", error);
  		vc->error = error;
  		goto iterate_address;
  
  	case -ECONNRESET:
  		_debug("call reset");
  		vc->error = error;
  		vc->flags |= AFS_VL_CURSOR_RETRY;
  		goto next_server;

  
  	case -EOPNOTSUPP:
  		_debug("notsupp");
  		goto next_server;

  	}
  
  restart_from_beginning:
  	_debug("restart");
  	afs_end_cursor(&vc->ac);
  	afs_put_vlserverlist(vc->cell->net, vc->server_list);
  	vc->server_list = NULL;
  	if (vc->flags & AFS_VL_CURSOR_RETRIED)
  		goto failed;
  	vc->flags |= AFS_VL_CURSOR_RETRIED;
  start:
  	_debug("start");

  	if (!afs_start_vl_iteration(vc))
  		goto failed;

  	error = afs_send_vl_probes(vc->cell->net, vc->key, vc->server_list);
  	if (error < 0)
  		goto failed_set_error;
  
  pick_server:
  	_debug("pick [%lx]", vc->untried);
  
  	error = afs_wait_for_vl_probes(vc->server_list, vc->untried);
  	if (error < 0)
  		goto failed_set_error;
  
  	/* Pick the untried server with the lowest RTT. */
  	vc->index = vc->server_list->preferred;
  	if (test_bit(vc->index, &vc->untried))
  		goto selected_server;
  
  	vc->index = -1;
  	rtt = U32_MAX;
  	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) ||

  		    !test_bit(AFS_VLSERVER_FL_RESPONDING, &s->flags))

  			continue;
  		if (s->probe.rtt < rtt) {
  			vc->index = i;
  			rtt = s->probe.rtt;
  		}
  	}
  
  	if (vc->index == -1)
  		goto no_more_servers;
  
  selected_server:
  	_debug("use %d", vc->index);
  	__clear_bit(vc->index, &vc->untried);

  	/* We're starting on a different vlserver from the list.  We need to
  	 * check it, find its address list and probe its capabilities before we
  	 * use it.
  	 */
  	ASSERTCMP(vc->ac.alist, ==, NULL);
  	vlserver = vc->server_list->servers[vc->index].server;

  	vc->server = vlserver;

  
  	_debug("USING VLSERVER: %s", vlserver->name);
  
  	read_lock(&vlserver->lock);
  	alist = rcu_dereference_protected(vlserver->addresses,
  					  lockdep_is_held(&vlserver->lock));
  	afs_get_addrlist(alist);
  	read_unlock(&vlserver->lock);
  
  	memset(&vc->ac, 0, sizeof(vc->ac));

  	if (!vc->ac.alist)
  		vc->ac.alist = alist;
  	else
  		afs_put_addrlist(alist);

  	vc->ac.index = -1;

  
  iterate_address:
  	ASSERT(vc->ac.alist);

  	/* Iterate over the current server's address list to try and find an
  	 * address on which it will respond to us.
  	 */
  	if (!afs_iterate_addresses(&vc->ac))
  		goto next_server;

  	_debug("VL address %d/%d", vc->ac.index, vc->ac.alist->nr_addrs);

  	_leave(" = t %pISpc", &vc->ac.alist->addrs[vc->ac.index].transport);

  	return true;
  
  next_server:
  	_debug("next");
  	afs_end_cursor(&vc->ac);

  	goto pick_server;

  no_more_servers:

  	/* That's all the servers poked to no good effect.  Try again if some
  	 * of them were busy.
  	 */
  	if (vc->flags & AFS_VL_CURSOR_RETRY)
  		goto restart_from_beginning;

  	e.error = -EDESTADDRREQ;
  	e.responded = false;

  	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:
  	vc->flags |= AFS_VL_CURSOR_STOP;
  	afs_end_cursor(&vc->ac);
  	_leave(" = f [failed %d]", vc->error);
  	return false;
  }
  
  /*

   * Dump cursor state in the case of the error being EDESTADDRREQ.
   */
  static void afs_vl_dump_edestaddrreq(const struct afs_vl_cursor *vc)
  {
  	static int count;
  	int i;
  
  	if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
  		return;
  	count++;
  
  	rcu_read_lock();
  	pr_notice("EDESTADDR occurred
  ");

  	pr_notice("VC: ut=%lx ix=%u ni=%hu fl=%hx err=%hd
  ",
  		  vc->untried, vc->index, vc->nr_iterations, vc->flags, vc->error);

  
  	if (vc->server_list) {
  		const struct afs_vlserver_list *sl = vc->server_list;
  		pr_notice("VC: SL nr=%u ix=%u
  ",
  			  sl->nr_servers, sl->index);
  		for (i = 0; i < sl->nr_servers; i++) {
  			const struct afs_vlserver *s = sl->servers[i].server;

  			pr_notice("VC: server %s+%hu fl=%lx E=%hd
  ",
  				  s->name, s->port, s->flags, s->probe.error);

  			if (s->addresses) {
  				const struct afs_addr_list *a =
  					rcu_dereference(s->addresses);

  				pr_notice("VC:  - nr=%u/%u/%u pf=%u
  ",

  					  a->nr_ipv4, a->nr_addrs, a->max_addrs,

  					  a->preferred);

  				pr_notice("VC:  - R=%lx F=%lx
  ",
  					  a->responded, a->failed);

  				if (a == vc->ac.alist)
  					pr_notice("VC:  - current
  ");
  			}
  		}
  	}

  	pr_notice("AC: t=%lx ax=%u ac=%d er=%d r=%u ni=%u
  ",
  		  vc->ac.tried, vc->ac.index, vc->ac.abort_code, vc->ac.error,
  		  vc->ac.responded, vc->ac.nr_iterations);

  	rcu_read_unlock();
  }
  
  /*

   * Tidy up a volume location server cursor and unlock the vnode.
   */
  int afs_end_vlserver_operation(struct afs_vl_cursor *vc)
  {
  	struct afs_net *net = vc->cell->net;

  	if (vc->error == -EDESTADDRREQ ||

  	    vc->error == -EADDRNOTAVAIL ||

  	    vc->error == -ENETUNREACH ||
  	    vc->error == -EHOSTUNREACH)
  		afs_vl_dump_edestaddrreq(vc);

  	afs_end_cursor(&vc->ac);
  	afs_put_vlserverlist(net, vc->server_list);
  
  	if (vc->error == -ECONNABORTED)
  		vc->error = afs_abort_to_error(vc->ac.abort_code);
  
  	return vc->error;
  }