// 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;

struct afs_endpoint_state *afs_get_endpoint_state(struct afs_endpoint_state *estate,
                                                  enum afs_estate_trace where)
{
        if (estate) {
                int r;

                __refcount_inc(&estate->ref, &r);
                trace_afs_estate(estate->server_id, estate->probe_seq, r, where);
        }
        return estate;
}

static void afs_endpoint_state_rcu(struct rcu_head *rcu)
{
        struct afs_endpoint_state *estate = container_of(rcu, struct afs_endpoint_state, rcu);

        trace_afs_estate(estate->server_id, estate->probe_seq, refcount_read(&estate->ref),
                         afs_estate_trace_free);
        afs_put_addrlist(estate->addresses, afs_alist_trace_put_estate);
        kfree(estate);
}

void afs_put_endpoint_state(struct afs_endpoint_state *estate, enum afs_estate_trace where)
{
        if (estate) {
                unsigned int server_id = estate->server_id, probe_seq = estate->probe_seq;
                bool dead;
                int r;

                dead = __refcount_dec_and_test(&estate->ref, &r);
                trace_afs_estate(server_id, probe_seq, r, where);
                if (dead)
                        call_rcu(&estate->rcu, afs_endpoint_state_rcu);
        }
}

/*
 * 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,
                                  struct afs_endpoint_state *estate)
{
        bool responded = test_bit(AFS_ESTATE_RESPONDED, &estate->flags);

        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,
                                  struct afs_endpoint_state *estate)
{
        _enter("");

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

        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_endpoint_state *estate,
                                  int index)
{
        _enter("");

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

        set_bit(AFS_ESTATE_LOCAL_FAILURE, &estate->flags);
        if (estate->error == 0)
                estate->error = -ENOMEM;

        set_bit(index, &estate->failed_set);

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

/*
 * 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_endpoint_state *estate = call->probe;
        struct afs_addr_list *alist = estate->addresses;
        struct afs_address *addr = &alist->addrs[call->probe_index];
        struct afs_server *server = call->server;
        unsigned int index = call->probe_index;
        unsigned int rtt_us = -1, cap0;
        int ret = call->error;

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

        WRITE_ONCE(addr->last_error, ret);

        spin_lock(&server->probe_lock);

        switch (ret) {
        case 0:
                estate->error = 0;
                goto responded;
        case -ECONNABORTED:
                if (!test_bit(AFS_ESTATE_RESPONDED, &estate->flags)) {
                        estate->abort_code = call->abort_code;
                        estate->error = ret;
                }
                goto responded;
        case -ENOMEM:
        case -ENONET:
                clear_bit(index, &estate->responsive_set);
                set_bit(AFS_ESTATE_LOCAL_FAILURE, &estate->flags);
                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, &estate->responsive_set);
                set_bit(index, &estate->failed_set);
                if (!test_bit(AFS_ESTATE_RESPONDED, &estate->flags) &&
                    (estate->error == 0 ||
                     estate->error == -ETIMEDOUT ||
                     estate->error == -ETIME))
                        estate->error = ret;
                trace_afs_io_error(call->debug_id, ret, afs_io_error_fs_probe_fail);
                goto out;
        }

responded:
        clear_bit(index, &estate->failed_set);

        if (call->service_id == YFS_FS_SERVICE) {
                set_bit(AFS_ESTATE_IS_YFS, &estate->flags);
                set_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
                server->service_id = call->service_id;
        } else {
                set_bit(AFS_ESTATE_NOT_YFS, &estate->flags);
                if (!test_bit(AFS_ESTATE_IS_YFS, &estate->flags)) {
                        clear_bit(AFS_SERVER_FL_IS_YFS, &server->flags);
                        server->service_id = 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);
        }

        rtt_us = rxrpc_kernel_get_srtt(addr->peer);
        if (rtt_us < estate->rtt) {
                estate->rtt = rtt_us;
                server->rtt = rtt_us;
                alist->preferred = index;
        }

        smp_wmb(); /* Set rtt before responded. */
        set_bit(AFS_ESTATE_RESPONDED, &estate->flags);
        set_bit(index, &estate->responsive_set);
        set_bit(AFS_SERVER_FL_RESPONDING, &server->flags);
out:
        spin_unlock(&server->probe_lock);

        trace_afs_fs_probe(server, false, estate, index, call->error, call->abort_code, rtt_us);
        _debug("probe[%x] %pU [%u] %pISpc rtt=%d ret=%d",
               estate->probe_seq, &server->uuid, index,
               rxrpc_kernel_remote_addr(alist->addrs[index].peer),
               rtt_us, ret);

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

/*
 * Probe all of a fileserver's addresses to find out the best route and to
 * query its capabilities.
 */
int afs_fs_probe_fileserver(struct afs_net *net, struct afs_server *server,
                            struct afs_addr_list *new_alist, struct key *key)
{
        struct afs_endpoint_state *estate, *old;
        struct afs_addr_list *old_alist = NULL, *alist;
        unsigned long unprobed;

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

        estate = kzalloc_obj(*estate);
        if (!estate)
                return -ENOMEM;

        refcount_set(&estate->ref, 2);
        estate->server_id = server->debug_id;
        estate->rtt = UINT_MAX;

        write_lock(&server->fs_lock);

        old = rcu_dereference_protected(server->endpoint_state,
                                        lockdep_is_held(&server->fs_lock));
        if (old) {
                estate->responsive_set = old->responsive_set;
                if (!new_alist)
                        new_alist = old->addresses;
        }

        if (old_alist != new_alist)
                afs_set_peer_appdata(server, old_alist, new_alist);

        estate->addresses = afs_get_addrlist(new_alist, afs_alist_trace_get_estate);
        alist = estate->addresses;
        estate->probe_seq = ++server->probe_counter;
        atomic_set(&estate->nr_probing, alist->nr_addrs);

        if (new_alist)
                server->addr_version = new_alist->version;
        rcu_assign_pointer(server->endpoint_state, estate);
        write_unlock(&server->fs_lock);
        if (old)
                set_bit(AFS_ESTATE_SUPERSEDED, &old->flags);

        trace_afs_estate(estate->server_id, estate->probe_seq, refcount_read(&estate->ref),
                         afs_estate_trace_alloc_probe);

        afs_get_address_preferences(net, new_alist);

        server->probed_at = jiffies;
        unprobed = (1UL << alist->nr_addrs) - 1;
        while (unprobed) {
                unsigned int index = 0, i;
                int best_prio = -1;

                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_fs_probe(server, true, estate, index, 0, 0, 0);
                if (!afs_fs_get_capabilities(net, server, estate, index, key))
                        afs_fs_probe_not_done(net, server, estate, index);
        }

        afs_put_endpoint_state(old, afs_estate_trace_put_probe);
        afs_put_endpoint_state(estate, afs_estate_trace_put_probe);
        return 0;
}

/*
 * Wait for the first as-yet untried fileserver to respond, for the probe state
 * to be superseded or for all probes to finish.
 */
int afs_wait_for_fs_probes(struct afs_operation *op, struct afs_server_state *states, bool intr)
{
        struct afs_endpoint_state *estate;
        struct afs_server_list *slist = op->server_list;
        bool still_probing = true;
        int ret = 0, i;

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

        for (i = 0; i < slist->nr_servers; i++) {
                estate = states[i].endpoint_state;
                if (test_bit(AFS_ESTATE_SUPERSEDED, &estate->flags))
                        return 2;
                if (atomic_read(&estate->nr_probing))
                        still_probing = true;
                if (estate->responsive_set & states[i].untried_addrs)
                        return 1;
        }
        if (!still_probing)
                return 0;

        for (i = 0; i < slist->nr_servers; i++)
                add_wait_queue(&slist->servers[i].server->probe_wq, &states[i].probe_waiter);

        for (;;) {
                still_probing = false;

                set_current_state(intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
                for (i = 0; i < slist->nr_servers; i++) {
                        estate = states[i].endpoint_state;
                        if (test_bit(AFS_ESTATE_SUPERSEDED, &estate->flags)) {
                                ret = 2;
                                goto stop;
                        }
                        if (atomic_read(&estate->nr_probing))
                                still_probing = true;
                        if (estate->responsive_set & states[i].untried_addrs) {
                                ret = 1;
                                goto stop;
                        }
                }

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

stop:
        set_current_state(TASK_RUNNING);

        for (i = 0; i < slist->nr_servers; i++)
                remove_wait_queue(&slist->servers[i].server->probe_wq, &states[i].probe_waiter);

        if (!ret && signal_pending(current))
                ret = -ERESTARTSYS;
        return ret;
}

/*
 * 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)
        __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, NULL, key);
        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);
        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) {
                afs_dec_servers_outstanding(net);
                return;
        }

        _enter("");

        if (list_empty(&net->fs_probe_fast) && list_empty(&net->fs_probe_slow)) {
                afs_dec_servers_outstanding(net);
                _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);
                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, struct afs_endpoint_state *estate,
                              unsigned long exclude, bool is_intr)
{
        struct wait_queue_entry wait;
        unsigned long timo = 2 * HZ;

        if (atomic_read(&estate->nr_probing) == 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 ||
                    test_bit(AFS_ESTATE_SUPERSEDED, &estate->flags) ||
                    (estate->responsive_set & ~exclude) ||
                    atomic_read(&estate->nr_probing) == 0 ||
                    (is_intr && signal_pending(current)))
                        break;
                timo = schedule_timeout(timo);
        }

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

dont_wait:
        if (test_bit(AFS_ESTATE_SUPERSEDED, &estate->flags))
                return 0;
        if (estate->responsive_set & ~exclude)
                return 1;
        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 (timer_delete_sync(&net->fs_probe_timer))
                afs_dec_servers_outstanding(net);
}