// 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"


/*
 * Handle the completion of a set of probes.
 */
static void afs_finished_vl_probe(struct afs_vlserver *server)
{
        if (!(server->probe.flags & AFS_VLSERVER_PROBE_RESPONDED)) {
                server->rtt = UINT_MAX;
                clear_bit(AFS_VLSERVER_FL_RESPONDING, &server->flags);
        }

        clear_bit_unlock(AFS_VLSERVER_FL_PROBING, &server->flags);
        wake_up_bit(&server->flags, AFS_VLSERVER_FL_PROBING);
}

/*
 * Handle the completion of a probe RPC call.
 */
static void afs_done_one_vl_probe(struct afs_vlserver *server, bool wake_up)
{
        if (atomic_dec_and_test(&server->probe_outstanding)) {
                afs_finished_vl_probe(server);
                wake_up = true;
        }

        if (wake_up)
                wake_up_all(&server->probe_wq);
}

/*
 * 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->vl_probe;
        struct afs_vlserver *server = call->vlserver;
        struct afs_address *addr = &alist->addrs[call->probe_index];
        unsigned int server_index = call->server_index;
        unsigned int rtt_us = 0;
        unsigned int index = call->probe_index;
        bool have_result = false;
        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.flags & AFS_VLSERVER_PROBE_RESPONDED)) {
                        server->probe.abort_code = call->abort_code;
                        server->probe.error = ret;
                }
                goto responded;
        case -ENOMEM:
        case -ENONET:
        case -EKEYEXPIRED:
        case -EKEYREVOKED:
        case -EKEYREJECTED:
                server->probe.flags |= AFS_VLSERVER_PROBE_LOCAL_FAILURE;
                if (server->probe.error == 0)
                        server->probe.error = ret;
                trace_afs_io_error(call->debug_id, ret, 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->probe_failed);
                if (!(server->probe.flags & AFS_VLSERVER_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_vl_probe_fail);
                goto out;
        }

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

        if (call->service_id == YFS_VL_SERVICE) {
                server->probe.flags |= AFS_VLSERVER_PROBE_IS_YFS;
                set_bit(AFS_VLSERVER_FL_IS_YFS, &server->flags);
                server->service_id = call->service_id;
        } else {
                server->probe.flags |= AFS_VLSERVER_PROBE_NOT_YFS;
                if (!(server->probe.flags & AFS_VLSERVER_PROBE_IS_YFS)) {
                        clear_bit(AFS_VLSERVER_FL_IS_YFS, &server->flags);
                        server->service_id = call->service_id;
                }
        }

        rtt_us = rxrpc_kernel_get_srtt(addr->peer);
        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.flags |= AFS_VLSERVER_PROBE_RESPONDED;
        set_bit(AFS_VLSERVER_FL_PROBED, &server->flags);
        set_bit(AFS_VLSERVER_FL_RESPONDING, &server->flags);
        have_result = true;
out:
        spin_unlock(&server->probe_lock);

        trace_afs_vl_probe(server, false, alist, index, call->error, call->abort_code, rtt_us);
        _debug("probe [%u][%u] %pISpc rtt=%d ret=%d",
               server_index, index, rxrpc_kernel_remote_addr(addr->peer),
               rtt_us, ret);

        afs_done_one_vl_probe(server, have_result);
}

/*
 * 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_list *alist;
        struct afs_call *call;
        unsigned long unprobed;
        unsigned int index, i;
        bool in_progress = false;
        int best_prio;

        _enter("%s", server->name);

        read_lock(&server->lock);
        alist = rcu_dereference_protected(server->addresses,
                                          lockdep_is_held(&server->lock));
        afs_get_addrlist(alist, afs_alist_trace_get_vlprobe);
        read_unlock(&server->lock);

        atomic_set(&server->probe_outstanding, alist->nr_addrs);
        memset(&server->probe, 0, sizeof(server->probe));
        server->probe.rtt = UINT_MAX;

        unprobed = (1UL << alist->nr_addrs) - 1;
        while (unprobed) {
                best_prio = -1;
                index = 0;
                for (i = 0; i < alist->nr_addrs; i++) {
                        if (test_bit(i, &unprobed) &&
                            alist->addrs[i].prio > best_prio) {
                                index = i;
                                best_prio = alist->addrs[i].prio;
                        }
                }
                __clear_bit(index, &unprobed);

                trace_afs_vl_probe(server, true, alist, index, 0, 0, 0);
                call = afs_vl_get_capabilities(net, alist, index, key, server,
                                               server_index);
                if (!IS_ERR(call)) {
                        afs_prioritise_error(_e, call->error, call->abort_code);
                        afs_put_call(call);
                        in_progress = true;
                } else {
                        afs_prioritise_error(_e, PTR_ERR(call), 0);
                        afs_done_one_vl_probe(server, false);
                }
        }

        afs_put_addrlist(alist, afs_alist_trace_put_vlprobe);
        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;

        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, rtt_s;
        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.flags & AFS_VLSERVER_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.flags & AFS_VLSERVER_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;
                        rtt_s = READ_ONCE(server->rtt);
                        if (test_bit(AFS_VLSERVER_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)
                vllist->preferred = pref;

        _leave(" = 0 [%u]", pref);
        return 0;
}