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

  /* AFS vlserver probing
   *
   * Copyright (C) 2018 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 bool afs_vl_probe_done(struct afs_vlserver *server)
  {
  	if (!atomic_dec_and_test(&server->probe_outstanding))
  		return false;
  
  	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;
  }
  
  /*
   * Process the result of probing a vlserver.  This is called after successful
   * or failed delivery of an VL.GetCapabilities operation.
   */
  void afs_vlserver_probe_result(struct afs_call *call)
  {
  	struct afs_addr_list *alist = call->alist;

  	struct afs_vlserver *server = call->vlserver;
  	unsigned int server_index = call->server_index;

  	unsigned int index = call->addr_ix;
  	unsigned int rtt = UINT_MAX;
  	bool have_result = false;
  	u64 _rtt;
  	int ret = call->error;
  
  	_enter("%s,%u,%u,%d,%d", server->name, server_index, index, ret, call->abort_code);
  
  	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:
  		server->probe.local_failure = true;
  		afs_io_error(call, afs_io_error_vl_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;
  		afs_io_error(call, afs_io_error_vl_probe_fail);
  		goto out;
  	}
  
  responded:
  	set_bit(index, &alist->responded);
  	clear_bit(index, &alist->failed);
  
  	if (call->service_id == YFS_VL_SERVICE) {
  		server->probe.is_yfs = true;
  		set_bit(AFS_VLSERVER_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_VLSERVER_FL_IS_YFS, &server->flags);
  			alist->addrs[index].srx_service = call->service_id;
  		}
  	}
  
  	/* Get the RTT and scale it to fit into a 32-bit value that represents
  	 * over a minute of time so that we can access it with one instruction
  	 * on a 32-bit system.
  	 */
  	_rtt = rxrpc_kernel_get_rtt(call->net->socket, call->rxcall);
  	_rtt /= 64;
  	rtt = (_rtt > UINT_MAX) ? UINT_MAX : _rtt;
  	if (rtt < server->probe.rtt) {
  		server->probe.rtt = rtt;
  		alist->preferred = index;
  		have_result = true;
  	}
  
  	smp_wmb(); /* Set rtt before responded. */
  	server->probe.responded = true;
  	set_bit(AFS_VLSERVER_FL_PROBED, &server->flags);
  out:
  	spin_unlock(&server->probe_lock);
  
  	_debug("probe [%u][%u] %pISpc rtt=%u ret=%d",
  	       server_index, index, &alist->addrs[index].transport,
  	       (unsigned int)rtt, ret);
  
  	have_result |= afs_vl_probe_done(server);
  	if (have_result) {
  		server->probe.have_result = true;
  		wake_up_var(&server->probe.have_result);
  		wake_up_all(&server->probe_wq);
  	}
  }
  
  /*
   * Probe all of a vlserver's addresses to find out the best route and to
   * query its capabilities.
   */

  static bool afs_do_probe_vlserver(struct afs_net *net,
  				  struct afs_vlserver *server,
  				  struct key *key,
  				  unsigned int server_index,
  				  struct afs_error *_e)

  {
  	struct afs_addr_cursor ac = {
  		.index = 0,
  	};

  	struct afs_call *call;

  	bool in_progress = false;

  
  	_enter("%s", server->name);
  
  	read_lock(&server->lock);
  	ac.alist = rcu_dereference_protected(server->addresses,
  					     lockdep_is_held(&server->lock));
  	read_unlock(&server->lock);
  
  	atomic_set(&server->probe_outstanding, ac.alist->nr_addrs);
  	memset(&server->probe, 0, sizeof(server->probe));
  	server->probe.rtt = UINT_MAX;
  
  	for (ac.index = 0; ac.index < ac.alist->nr_addrs; ac.index++) {

  		call = afs_vl_get_capabilities(net, &ac, key, server,
  					       server_index);
  		if (!IS_ERR(call)) {
  			afs_put_call(call);

  			in_progress = true;

  		} else {
  			afs_prioritise_error(_e, PTR_ERR(call), ac.abort_code);
  		}

  	}

  	if (!in_progress)
  		afs_vl_probe_done(server);
  	return in_progress;

  }
  
  /*
   * Send off probes to all unprobed servers.
   */
  int afs_send_vl_probes(struct afs_net *net, struct key *key,
  		       struct afs_vlserver_list *vllist)
  {
  	struct afs_vlserver *server;

  	struct afs_error e;
  	bool in_progress = false;
  	int i;

  	e.error = 0;
  	e.responded = false;

  	for (i = 0; i < vllist->nr_servers; i++) {
  		server = vllist->servers[i].server;
  		if (test_bit(AFS_VLSERVER_FL_PROBED, &server->flags))
  			continue;

  		if (!test_and_set_bit_lock(AFS_VLSERVER_FL_PROBING, &server->flags) &&
  		    afs_do_probe_vlserver(net, server, key, i, &e))
  			in_progress = true;

  	}

  	return in_progress ? 0 : e.error;

  }
  
  /*
   * Wait for the first as-yet untried server to respond.
   */
  int afs_wait_for_vl_probes(struct afs_vlserver_list *vllist,
  			   unsigned long untried)
  {
  	struct wait_queue_entry *waits;
  	struct afs_vlserver *server;
  	unsigned int rtt = UINT_MAX;
  	bool have_responders = false;
  	int pref = -1, i;
  
  	_enter("%u,%lx", vllist->nr_servers, untried);
  
  	/* Only wait for servers that have a probe outstanding. */
  	for (i = 0; i < vllist->nr_servers; i++) {
  		if (test_bit(i, &untried)) {
  			server = vllist->servers[i].server;
  			if (!test_bit(AFS_VLSERVER_FL_PROBING, &server->flags))
  				__clear_bit(i, &untried);
  			if (server->probe.responded)
  				have_responders = true;
  		}
  	}
  	if (have_responders || !untried)
  		return 0;
  
  	waits = kmalloc(array_size(vllist->nr_servers, sizeof(*waits)), GFP_KERNEL);
  	if (!waits)
  		return -ENOMEM;
  
  	for (i = 0; i < vllist->nr_servers; i++) {
  		if (test_bit(i, &untried)) {
  			server = vllist->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 < vllist->nr_servers; i++) {
  			if (test_bit(i, &untried)) {
  				server = vllist->servers[i].server;
  				if (server->probe.responded)
  					goto stop;
  				if (test_bit(AFS_VLSERVER_FL_PROBING, &server->flags))
  					still_probing = true;
  			}
  		}

  		if (!still_probing || signal_pending(current))

  			goto stop;
  		schedule();
  	}
  
  stop:
  	set_current_state(TASK_RUNNING);
  
  	for (i = 0; i < vllist->nr_servers; i++) {
  		if (test_bit(i, &untried)) {
  			server = vllist->servers[i].server;
  			if (server->probe.responded &&
  			    server->probe.rtt < rtt) {
  				pref = i;
  				rtt = server->probe.rtt;
  			}
  
  			remove_wait_queue(&server->probe_wq, &waits[i]);
  		}
  	}
  
  	kfree(waits);
  
  	if (pref == -1 && signal_pending(current))
  		return -ERESTARTSYS;
  
  	if (pref >= 0)
  		vllist->preferred = pref;
  
  	_leave(" = 0 [%u]", pref);
  	return 0;
  }