// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS fileserver probing
 *
 * Copyright (C) 2018, 2020 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_afs.h"
#include "protocol_yfs.h"

static unsigned int afs_fs_probe_fast_poll_interval = 30 * HZ;
static unsigned int afs_fs_probe_slow_poll_interval = 5 * 60 * HZ;

/*
 * Start the probe polling timer.  We have to supply it with an inc on the
 * outstanding server count.
 */
static void afs_schedule_fs_probe(struct afs_net *net,
                                  struct afs_server *server, bool fast)
{
        unsigned long atj;

        if (!net->live)
                return;

        atj = server->probed_at;
        atj += fast ? afs_fs_probe_fast_poll_interval : afs_fs_probe_slow_poll_interval;

        afs_inc_servers_outstanding(net);
        if (timer_reduce(&net->fs_probe_timer, atj))
                afs_dec_servers_outstanding(net);
}

/*
 * Handle the completion of a set of probes.
 */
static void afs_finished_fs_probe(struct afs_net *net, struct afs_server *server)
{
        bool responded = server->probe.responded;

        write_seqlock(&net->fs_lock);
        if (responded) {
                list_add_tail(&server->probe_link, &net->fs_probe_slow);
        } else {
                server->rtt = UINT_MAX;
                clear_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
                list_add_tail(&server->probe_link, &net->fs_probe_fast);
        }
        write_sequnlock(&net->fs_lock);

        afs_schedule_fs_probe(net, server, !responded);
}

/*
 * Handle the completion of a probe.
 */
static void afs_done_one_fs_probe(struct afs_net *net, struct afs_server *server)
{
        _enter("");

        if (atomic_dec_and_test(&server->probe_outstanding))
                afs_finished_fs_probe(net, server);

        wake_up_all(&server->probe_wq);
}

/*
 * Handle inability to send a probe due to ENOMEM when trying to allocate a
 * call struct.
 */
static void afs_fs_probe_not_done(struct afs_net *net,
                                  struct afs_server *server,
                                  struct afs_addr_cursor *ac)
{
        struct afs_addr_list *alist = ac->alist;
        unsigned int index = ac->index;

        _enter("");

        trace_afs_io_error(0, -ENOMEM, afs_io_error_fs_probe_fail);
        spin_lock(&server->probe_lock);

        server->probe.local_failure = true;
        if (server->probe.error == 0)
                server->probe.error = -ENOMEM;

        set_bit(index, &alist->failed);

        spin_unlock(&server->probe_lock);
        return afs_done_one_fs_probe(net, server);
}

/*
 * Process the result of probing a fileserver.  This is called after successful
 * or failed delivery of an FS.GetCapabilities operation.
 */
void afs_fileserver_probe_result(struct afs_call *call)
{
        struct afs_addr_list *alist = call->alist;
        struct afs_server *server = call->server;
        unsigned int index = call->addr_ix;
        unsigned int rtt_us = 0, cap0;
        int ret = call->error;

        _enter("%pU,%u", &server->uuid, index);

        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:
                clear_bit(index, &alist->responded);
                server->probe.local_failure = true;
                trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_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;
                trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_probe_fail);
                goto out;
        }

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

        if (call->service_id == YFS_FS_SERVICE) {
                server->probe.is_yfs = true;
                set_bit(AFS_SERVER_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_SERVER_FL_IS_YFS, &server->flags);
                        alist->addrs[index].srx_service = call->service_id;
                }
                cap0 = ntohl(call->tmp);
                if (cap0 & AFS3_VICED_CAPABILITY_64BITFILES)
                        set_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
                else
                        clear_bit(AFS_SERVER_FL_HAS_FS64, &server->flags);
        }

        if (rxrpc_kernel_get_srtt(call->net->socket, call->rxcall, &rtt_us) &&
            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.responded = true;
        set_bit(index, &alist->responded);
        set_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
out:
        spin_unlock(&server->probe_lock);

        _debug("probe %pU [%u] %pISpc rtt=%u ret=%d",
               &server->uuid, index, &alist->addrs[index].transport,
               rtt_us, ret);

        return afs_done_one_fs_probe(call->net, server);
}

/*
 * Probe one or all of a fileserver's addresses to find out the best route and
 * to query its capabilities.
 */
void afs_fs_probe_fileserver(struct afs_net *net, struct afs_server *server,
                             struct key *key, bool all)
{
        struct afs_addr_cursor ac = {
                .index = 0,
        };

        _enter("%pU", &server->uuid);

        read_lock(&server->fs_lock);
        ac.alist = rcu_dereference_protected(server->addresses,
                                             lockdep_is_held(&server->fs_lock));
        afs_get_addrlist(ac.alist);
        read_unlock(&server->fs_lock);

        server->probed_at = jiffies;
        atomic_set(&server->probe_outstanding, all ? ac.alist->nr_addrs : 1);
        memset(&server->probe, 0, sizeof(server->probe));
        server->probe.rtt = UINT_MAX;

        ac.index = ac.alist->preferred;
        if (ac.index < 0 || ac.index >= ac.alist->nr_addrs)
                all = true;

        if (all) {
                for (ac.index = 0; ac.index < ac.alist->nr_addrs; ac.index++)
                        if (!afs_fs_get_capabilities(net, server, &ac, key))
                                afs_fs_probe_not_done(net, server, &ac);
        } else {
                if (!afs_fs_get_capabilities(net, server, &ac, key))
                        afs_fs_probe_not_done(net, server, &ac);
        }

        afs_put_addrlist(ac.alist);
}

/*
 * Wait for the first as-yet untried fileserver to respond.
 */
int afs_wait_for_fs_probes(struct afs_server_list *slist, unsigned long untried)
{
        struct wait_queue_entry *waits;
        struct afs_server *server;
        unsigned int rtt = UINT_MAX, rtt_s;
        bool have_responders = false;
        int pref = -1, i;

        _enter("%u,%lx", slist->nr_servers, untried);

        /* Only wait for servers that have a probe outstanding. */
        for (i = 0; i < slist->nr_servers; i++) {
                if (test_bit(i, &untried)) {
                        server = slist->servers[i].server;
                        if (!atomic_read(&server->probe_outstanding))
                                __clear_bit(i, &untried);
                        if (server->probe.responded)
                                have_responders = true;
                }
        }
        if (have_responders || !untried)
                return 0;

        waits = kmalloc(array_size(slist->nr_servers, sizeof(*waits)), GFP_KERNEL);
        if (!waits)
                return -ENOMEM;

        for (i = 0; i < slist->nr_servers; i++) {
                if (test_bit(i, &untried)) {
                        server = slist->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 < slist->nr_servers; i++) {
                        if (test_bit(i, &untried)) {
                                server = slist->servers[i].server;
                                if (server->probe.responded)
                                        goto stop;
                                if (atomic_read(&server->probe_outstanding))
                                        still_probing = true;
                        }
                }

                if (!still_probing || signal_pending(current))
                        goto stop;
                schedule();
        }

stop:
        set_current_state(TASK_RUNNING);

        for (i = 0; i < slist->nr_servers; i++) {
                if (test_bit(i, &untried)) {
                        server = slist->servers[i].server;
                        rtt_s = READ_ONCE(server->rtt);
                        if (test_bit(AFS_SERVER_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)
                slist->preferred = pref;
        return 0;
}

/*
 * Probe timer.  We have an increment on fs_outstanding that we need to pass
 * along to the work item.
 */
void afs_fs_probe_timer(struct timer_list *timer)
{
        struct afs_net *net = container_of(timer, struct afs_net, fs_probe_timer);

        if (!net->live || !queue_work(afs_wq, &net->fs_prober))
                afs_dec_servers_outstanding(net);
}

/*
 * Dispatch a probe to a server.
 */
static void afs_dispatch_fs_probe(struct afs_net *net, struct afs_server *server, bool all)
        __releases(&net->fs_lock)
{
        struct key *key = NULL;

        /* We remove it from the queues here - it will be added back to
         * one of the queues on the completion of the probe.
         */
        list_del_init(&server->probe_link);

        afs_get_server(server, afs_server_trace_get_probe);
        write_sequnlock(&net->fs_lock);

        afs_fs_probe_fileserver(net, server, key, all);
        afs_put_server(net, server, afs_server_trace_put_probe);
}

/*
 * Probe a server immediately without waiting for its due time to come
 * round.  This is used when all of the addresses have been tried.
 */
void afs_probe_fileserver(struct afs_net *net, struct afs_server *server)
{
        write_seqlock(&net->fs_lock);
        if (!list_empty(&server->probe_link))
                return afs_dispatch_fs_probe(net, server, true);
        write_sequnlock(&net->fs_lock);
}

/*
 * Probe dispatcher to regularly dispatch probes to keep NAT alive.
 */
void afs_fs_probe_dispatcher(struct work_struct *work)
{
        struct afs_net *net = container_of(work, struct afs_net, fs_prober);
        struct afs_server *fast, *slow, *server;
        unsigned long nowj, timer_at, poll_at;
        bool first_pass = true, set_timer = false;

        if (!net->live)
                return;

        _enter("");

        if (list_empty(&net->fs_probe_fast) && list_empty(&net->fs_probe_slow)) {
                _leave(" [none]");
                return;
        }

again:
        write_seqlock(&net->fs_lock);

        fast = slow = server = NULL;
        nowj = jiffies;
        timer_at = nowj + MAX_JIFFY_OFFSET;

        if (!list_empty(&net->fs_probe_fast)) {
                fast = list_first_entry(&net->fs_probe_fast, struct afs_server, probe_link);
                poll_at = fast->probed_at + afs_fs_probe_fast_poll_interval;
                if (time_before(nowj, poll_at)) {
                        timer_at = poll_at;
                        set_timer = true;
                        fast = NULL;
                }
        }

        if (!list_empty(&net->fs_probe_slow)) {
                slow = list_first_entry(&net->fs_probe_slow, struct afs_server, probe_link);
                poll_at = slow->probed_at + afs_fs_probe_slow_poll_interval;
                if (time_before(nowj, poll_at)) {
                        if (time_before(poll_at, timer_at))
                            timer_at = poll_at;
                        set_timer = true;
                        slow = NULL;
                }
        }

        server = fast ?: slow;
        if (server)
                _debug("probe %pU", &server->uuid);

        if (server && (first_pass || !need_resched())) {
                afs_dispatch_fs_probe(net, server, server == fast);
                first_pass = false;
                goto again;
        }

        write_sequnlock(&net->fs_lock);

        if (server) {
                if (!queue_work(afs_wq, &net->fs_prober))
                        afs_dec_servers_outstanding(net);
                _leave(" [requeue]");
        } else if (set_timer) {
                if (timer_reduce(&net->fs_probe_timer, timer_at))
                        afs_dec_servers_outstanding(net);
                _leave(" [timer]");
        } else {
                afs_dec_servers_outstanding(net);
                _leave(" [quiesce]");
        }
}

/*
 * Wait for a probe on a particular fileserver to complete for 2s.
 */
int afs_wait_for_one_fs_probe(struct afs_server *server, bool is_intr)
{
        struct wait_queue_entry wait;
        unsigned long timo = 2 * HZ;

        if (atomic_read(&server->probe_outstanding) == 0)
                goto dont_wait;

        init_wait_entry(&wait, 0);
        for (;;) {
                prepare_to_wait_event(&server->probe_wq, &wait,
                                      is_intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
                if (timo == 0 ||
                    server->probe.responded ||
                    atomic_read(&server->probe_outstanding) == 0 ||
                    (is_intr && signal_pending(current)))
                        break;
                timo = schedule_timeout(timo);
        }

        finish_wait(&server->probe_wq, &wait);

dont_wait:
        if (server->probe.responded)
                return 0;
        if (is_intr && signal_pending(current))
                return -ERESTARTSYS;
        if (timo == 0)
                return -ETIME;
        return -EDESTADDRREQ;
}

/*
 * Clean up the probing when the namespace is killed off.
 */
void afs_fs_probe_cleanup(struct afs_net *net)
{
        if (del_timer_sync(&net->fs_probe_timer))
                afs_dec_servers_outstanding(net);
}