// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS server record management
 *
 * Copyright (C) 2002, 2007 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 unsigned afs_server_gc_delay = 10;       /* Server record timeout in seconds */
static atomic_t afs_server_debug_id;

static void __afs_put_server(struct afs_net *, struct afs_server *);
static void afs_server_timer(struct timer_list *timer);
static void afs_server_destroyer(struct work_struct *work);

/*
 * Find a server by one of its addresses.
 */
struct afs_server *afs_find_server(const struct rxrpc_peer *peer)
{
        struct afs_server *server = (struct afs_server *)rxrpc_kernel_get_peer_data(peer);

        if (!server)
                return NULL;
        return afs_use_server(server, false, afs_server_trace_use_cm_call);
}

/*
 * Look up a server by its UUID and mark it active.  The caller must hold
 * cell->fs_lock.
 */
static struct afs_server *afs_find_server_by_uuid(struct afs_cell *cell, const uuid_t *uuid)
{
        struct afs_server *server;
        struct rb_node *p;
        int diff;

        _enter("%pU", uuid);

        p = cell->fs_servers.rb_node;
        while (p) {
                server = rb_entry(p, struct afs_server, uuid_rb);

                diff = memcmp(uuid, &server->uuid, sizeof(*uuid));
                if (diff < 0) {
                        p = p->rb_left;
                } else if (diff > 0) {
                        p = p->rb_right;
                } else {
                        if (test_bit(AFS_SERVER_FL_UNCREATED, &server->flags))
                                return NULL; /* Need a write lock */
                        afs_use_server(server, true, afs_server_trace_use_by_uuid);
                        return server;
                }
        }

        return NULL;
}

/*
 * Install a server record in the cell tree.  The caller must hold an exclusive
 * lock on cell->fs_lock.
 */
static struct afs_server *afs_install_server(struct afs_cell *cell,
                                             struct afs_server **candidate)
{
        struct afs_server *server;
        struct afs_net *net = cell->net;
        struct rb_node **pp, *p;
        int diff;

        _enter("%p", candidate);

        /* Firstly install the server in the UUID lookup tree */
        pp = &cell->fs_servers.rb_node;
        p = NULL;
        while (*pp) {
                p = *pp;
                _debug("- consider %p", p);
                server = rb_entry(p, struct afs_server, uuid_rb);
                diff = memcmp(&(*candidate)->uuid, &server->uuid, sizeof(uuid_t));
                if (diff < 0)
                        pp = &(*pp)->rb_left;
                else if (diff > 0)
                        pp = &(*pp)->rb_right;
                else
                        goto exists;
        }

        server = *candidate;
        *candidate = NULL;
        rb_link_node(&server->uuid_rb, p, pp);
        rb_insert_color(&server->uuid_rb, &cell->fs_servers);
        write_seqlock(&net->fs_lock);
        hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
        write_sequnlock(&net->fs_lock);

        afs_get_cell(cell, afs_cell_trace_get_server);

exists:
        afs_use_server(server, true, afs_server_trace_use_install);
        return server;
}

/*
 * Allocate a new server record and mark it as active but uncreated.
 */
static struct afs_server *afs_alloc_server(struct afs_cell *cell, const uuid_t *uuid)
{
        struct afs_server *server;
        struct afs_net *net = cell->net;

        _enter("");

        server = kzalloc_obj(struct afs_server);
        if (!server)
                return NULL;

        refcount_set(&server->ref, 1);
        atomic_set(&server->active, 0);
        __set_bit(AFS_SERVER_FL_UNCREATED, &server->flags);
        server->debug_id = atomic_inc_return(&afs_server_debug_id);
        server->uuid = *uuid;
        rwlock_init(&server->fs_lock);
        INIT_WORK(&server->destroyer, &afs_server_destroyer);
        timer_setup(&server->timer, afs_server_timer, 0);
        INIT_LIST_HEAD(&server->volumes);
        init_waitqueue_head(&server->probe_wq);
        mutex_init(&server->cm_token_lock);
        INIT_LIST_HEAD(&server->probe_link);
        INIT_HLIST_NODE(&server->proc_link);
        spin_lock_init(&server->probe_lock);
        server->cell = cell;
        server->rtt = UINT_MAX;
        server->service_id = FS_SERVICE;
        server->probe_counter = 1;
        server->probed_at = jiffies - LONG_MAX / 2;

        afs_inc_servers_outstanding(net);
        _leave(" = %p", server);
        return server;
}

/*
 * Look up an address record for a server
 */
static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_server *server,
                                                 struct key *key)
{
        struct afs_vl_cursor vc;
        struct afs_addr_list *alist = NULL;
        int ret;

        ret = -ERESTARTSYS;
        if (afs_begin_vlserver_operation(&vc, server->cell, key)) {
                while (afs_select_vlserver(&vc)) {
                        if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
                                alist = afs_yfsvl_get_endpoints(&vc, &server->uuid);
                        else
                                alist = afs_vl_get_addrs_u(&vc, &server->uuid);
                }

                ret = afs_end_vlserver_operation(&vc);
        }

        return ret < 0 ? ERR_PTR(ret) : alist;
}

/*
 * Get or create a fileserver record and return it with an active-use count on
 * it.
 */
struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
                                     const uuid_t *uuid, u32 addr_version)
{
        struct afs_addr_list *alist = NULL;
        struct afs_server *server, *candidate = NULL;
        bool creating = false;
        int ret;

        _enter("%p,%pU", cell->net, uuid);

        down_read(&cell->fs_lock);
        server = afs_find_server_by_uuid(cell, uuid);
        /* Won't see servers marked uncreated. */
        up_read(&cell->fs_lock);

        if (server) {
                timer_delete_sync(&server->timer);
                if (test_bit(AFS_SERVER_FL_CREATING, &server->flags))
                        goto wait_for_creation;
                if (server->addr_version != addr_version)
                        set_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
                return server;
        }

        candidate = afs_alloc_server(cell, uuid);
        if (!candidate) {
                afs_put_addrlist(alist, afs_alist_trace_put_server_oom);
                return ERR_PTR(-ENOMEM);
        }

        down_write(&cell->fs_lock);
        server = afs_install_server(cell, &candidate);
        if (test_bit(AFS_SERVER_FL_CREATING, &server->flags)) {
                /* We need to wait for creation to complete. */
                up_write(&cell->fs_lock);
                goto wait_for_creation;
        }
        if (test_bit(AFS_SERVER_FL_UNCREATED, &server->flags)) {
                set_bit(AFS_SERVER_FL_CREATING, &server->flags);
                clear_bit(AFS_SERVER_FL_UNCREATED, &server->flags);
                creating = true;
        }
        up_write(&cell->fs_lock);
        timer_delete_sync(&server->timer);

        /* If we get to create the server, we look up the addresses and then
         * immediately dispatch an asynchronous probe to each interface on the
         * fileserver.  This will make sure the repeat-probing service is
         * started.
         */
        if (creating) {
                alist = afs_vl_lookup_addrs(server, key);
                if (IS_ERR(alist)) {
                        ret = PTR_ERR(alist);
                        goto create_failed;
                }

                ret = afs_fs_probe_fileserver(cell->net, server, alist, key);
                if (ret)
                        goto create_failed;

                clear_and_wake_up_bit(AFS_SERVER_FL_CREATING, &server->flags);
        }

out:
        afs_put_addrlist(alist, afs_alist_trace_put_server_create);
        if (candidate) {
                kfree(rcu_access_pointer(server->endpoint_state));
                kfree(candidate);
                afs_dec_servers_outstanding(cell->net);
        }
        return server ?: ERR_PTR(ret);

wait_for_creation:
        afs_see_server(server, afs_server_trace_wait_create);
        wait_on_bit(&server->flags, AFS_SERVER_FL_CREATING, TASK_UNINTERRUPTIBLE);
        if (test_bit_acquire(AFS_SERVER_FL_UNCREATED, &server->flags)) {
                /* Barrier: read flag before error */
                ret = READ_ONCE(server->create_error);
                afs_put_server(cell->net, server, afs_server_trace_unuse_create_fail);
                server = NULL;
                goto out;
        }

        ret = 0;
        goto out;

create_failed:
        down_write(&cell->fs_lock);

        WRITE_ONCE(server->create_error, ret);
        smp_wmb(); /* Barrier: set error before flag. */
        set_bit(AFS_SERVER_FL_UNCREATED, &server->flags);

        clear_and_wake_up_bit(AFS_SERVER_FL_CREATING, &server->flags);

        if (test_bit(AFS_SERVER_FL_UNCREATED, &server->flags)) {
                clear_bit(AFS_SERVER_FL_UNCREATED, &server->flags);
                creating = true;
        }
        afs_unuse_server(cell->net, server, afs_server_trace_unuse_create_fail);
        server = NULL;

        up_write(&cell->fs_lock);
        goto out;
}

/*
 * Set/reduce a server's timer.
 */
static void afs_set_server_timer(struct afs_server *server, unsigned int delay_secs)
{
        mod_timer(&server->timer, jiffies + delay_secs * HZ);
}

/*
 * Get a reference on a server object.
 */
struct afs_server *afs_get_server(struct afs_server *server,
                                  enum afs_server_trace reason)
{
        unsigned int a;
        int r;

        __refcount_inc(&server->ref, &r);
        a = atomic_read(&server->active);
        trace_afs_server(server->debug_id, r + 1, a, reason);
        return server;
}

/*
 * Get an active count on a server object and maybe remove from the inactive
 * list.
 */
struct afs_server *afs_use_server(struct afs_server *server, bool activate,
                                  enum afs_server_trace reason)
{
        unsigned int a;
        int r;

        __refcount_inc(&server->ref, &r);
        a = atomic_inc_return(&server->active);
        if (a == 1 && activate &&
            !test_bit(AFS_SERVER_FL_EXPIRED, &server->flags))
                timer_delete(&server->timer);

        trace_afs_server(server->debug_id, r + 1, a, reason);
        return server;
}

/*
 * Release a reference on a server record.
 */
void afs_put_server(struct afs_net *net, struct afs_server *server,
                    enum afs_server_trace reason)
{
        unsigned int a, debug_id;
        bool zero;
        int r;

        if (!server)
                return;

        debug_id = server->debug_id;
        a = atomic_read(&server->active);
        zero = __refcount_dec_and_test(&server->ref, &r);
        trace_afs_server(debug_id, r - 1, a, reason);
        if (unlikely(zero))
                __afs_put_server(net, server);
}

/*
 * Drop an active count on a server object without updating the last-unused
 * time.
 */
void afs_unuse_server_notime(struct afs_net *net, struct afs_server *server,
                             enum afs_server_trace reason)
{
        if (!server)
                return;

        if (atomic_dec_and_test(&server->active)) {
                if (test_bit(AFS_SERVER_FL_EXPIRED, &server->flags) ||
                    READ_ONCE(server->cell->state) >= AFS_CELL_REMOVING)
                        schedule_work(&server->destroyer);
        }

        afs_put_server(net, server, reason);
}

/*
 * Drop an active count on a server object.
 */
void afs_unuse_server(struct afs_net *net, struct afs_server *server,
                      enum afs_server_trace reason)
{
        if (!server)
                return;

        if (atomic_dec_and_test(&server->active)) {
                if (!test_bit(AFS_SERVER_FL_EXPIRED, &server->flags) &&
                    READ_ONCE(server->cell->state) < AFS_CELL_REMOVING) {
                        time64_t unuse_time = ktime_get_real_seconds();

                        server->unuse_time = unuse_time;
                        afs_set_server_timer(server, afs_server_gc_delay);
                } else {
                        schedule_work(&server->destroyer);
                }
        }

        afs_put_server(net, server, reason);
}

static void afs_server_rcu(struct rcu_head *rcu)
{
        struct afs_server *server = container_of(rcu, struct afs_server, rcu);

        trace_afs_server(server->debug_id, refcount_read(&server->ref),
                         atomic_read(&server->active), afs_server_trace_free);
        afs_put_endpoint_state(rcu_access_pointer(server->endpoint_state),
                               afs_estate_trace_put_server);
        afs_put_cell(server->cell, afs_cell_trace_put_server);
        kfree(server->cm_rxgk_appdata.data);
        kfree(server);
}

static void __afs_put_server(struct afs_net *net, struct afs_server *server)
{
        call_rcu(&server->rcu, afs_server_rcu);
        afs_dec_servers_outstanding(net);
}

static void afs_give_up_callbacks(struct afs_net *net, struct afs_server *server)
{
        struct afs_endpoint_state *estate = rcu_access_pointer(server->endpoint_state);
        struct afs_addr_list *alist = estate->addresses;

        afs_fs_give_up_all_callbacks(net, server, &alist->addrs[alist->preferred], NULL);
}

/*
 * Check to see if the server record has expired.
 */
static bool afs_has_server_expired(const struct afs_server *server)
{
        time64_t expires_at;

        if (atomic_read(&server->active))
                return false;

        if (server->cell->net->live ||
            server->cell->state >= AFS_CELL_REMOVING) {
                trace_afs_server(server->debug_id, refcount_read(&server->ref),
                                 0, afs_server_trace_purging);
                return true;
        }

        expires_at = server->unuse_time;
        if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
            !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
                expires_at += afs_server_gc_delay;

        return ktime_get_real_seconds() > expires_at;
}

/*
 * Remove a server record from it's parent cell's database.
 */
static bool afs_remove_server_from_cell(struct afs_server *server)
{
        struct afs_cell *cell = server->cell;

        down_write(&cell->fs_lock);

        if (!afs_has_server_expired(server)) {
                up_write(&cell->fs_lock);
                return false;
        }

        set_bit(AFS_SERVER_FL_EXPIRED, &server->flags);
        _debug("expire %pU %u", &server->uuid, atomic_read(&server->active));
        afs_see_server(server, afs_server_trace_see_expired);
        rb_erase(&server->uuid_rb, &cell->fs_servers);
        up_write(&cell->fs_lock);
        return true;
}

static void afs_server_destroyer(struct work_struct *work)
{
        struct afs_endpoint_state *estate;
        struct afs_server *server = container_of(work, struct afs_server, destroyer);
        struct afs_net *net = server->cell->net;

        afs_see_server(server, afs_server_trace_see_destroyer);

        if (test_bit(AFS_SERVER_FL_EXPIRED, &server->flags))
                return;

        if (!afs_remove_server_from_cell(server))
                return;

        timer_shutdown_sync(&server->timer);
        cancel_work(&server->destroyer);

        if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
                afs_give_up_callbacks(net, server);

        /* Unbind the rxrpc_peer records from the server. */
        estate = rcu_access_pointer(server->endpoint_state);
        if (estate)
                afs_set_peer_appdata(server, estate->addresses, NULL);

        write_seqlock(&net->fs_lock);
        list_del_init(&server->probe_link);
        if (!hlist_unhashed(&server->proc_link))
                hlist_del_rcu(&server->proc_link);
        write_sequnlock(&net->fs_lock);

        afs_put_server(net, server, afs_server_trace_destroy);
}

static void afs_server_timer(struct timer_list *timer)
{
        struct afs_server *server = container_of(timer, struct afs_server, timer);

        afs_see_server(server, afs_server_trace_see_timer);
        if (!test_bit(AFS_SERVER_FL_EXPIRED, &server->flags))
                schedule_work(&server->destroyer);
}

/*
 * Wake up all the servers in a cell so that they can purge themselves.
 */
void afs_purge_servers(struct afs_cell *cell)
{
        struct afs_server *server;
        struct rb_node *rb;

        down_read(&cell->fs_lock);
        for (rb = rb_first(&cell->fs_servers); rb; rb = rb_next(rb)) {
                server = rb_entry(rb, struct afs_server, uuid_rb);
                afs_see_server(server, afs_server_trace_see_purge);
                schedule_work(&server->destroyer);
        }
        up_read(&cell->fs_lock);
}

/*
 * Wait for outstanding servers.
 */
void afs_wait_for_servers(struct afs_net *net)
{
        _enter("");

        atomic_dec(&net->servers_outstanding);
        wait_var_event(&net->servers_outstanding,
                       !atomic_read(&net->servers_outstanding));
        _leave("");
}

/*
 * Get an update for a server's address list.
 */
static noinline bool afs_update_server_record(struct afs_operation *op,
                                              struct afs_server *server,
                                              struct key *key)
{
        struct afs_endpoint_state *estate;
        struct afs_addr_list *alist;
        bool has_addrs;

        _enter("");

        trace_afs_server(server->debug_id, refcount_read(&server->ref),
                         atomic_read(&server->active),
                         afs_server_trace_update);

        alist = afs_vl_lookup_addrs(server, op->key);
        if (IS_ERR(alist)) {
                rcu_read_lock();
                estate = rcu_dereference(server->endpoint_state);
                has_addrs = estate->addresses;
                rcu_read_unlock();

                if ((PTR_ERR(alist) == -ERESTARTSYS ||
                     PTR_ERR(alist) == -EINTR) &&
                    (op->flags & AFS_OPERATION_UNINTR) &&
                    has_addrs) {
                        _leave(" = t [intr]");
                        return true;
                }
                afs_op_set_error(op, PTR_ERR(alist));
                _leave(" = f [%d]", afs_op_error(op));
                return false;
        }

        if (server->addr_version != alist->version)
                afs_fs_probe_fileserver(op->net, server, alist, key);

        afs_put_addrlist(alist, afs_alist_trace_put_server_update);
        _leave(" = t");
        return true;
}

/*
 * See if a server's address list needs updating.
 */
bool afs_check_server_record(struct afs_operation *op, struct afs_server *server,
                             struct key *key)
{
        bool success;
        int ret, retries = 0;

        _enter("");

        ASSERT(server);

retry:
        if (test_bit(AFS_SERVER_FL_UPDATING, &server->flags))
                goto wait;
        if (test_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags))
                goto update;
        _leave(" = t [good]");
        return true;

update:
        if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
                clear_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
                success = afs_update_server_record(op, server, key);
                clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
                wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
                _leave(" = %d", success);
                return success;
        }

wait:
        ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
                          (op->flags & AFS_OPERATION_UNINTR) ?
                          TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
        if (ret == -ERESTARTSYS) {
                afs_op_set_error(op, ret);
                _leave(" = f [intr]");
                return false;
        }

        retries++;
        if (retries == 4) {
                _leave(" = f [stale]");
                ret = -ESTALE;
                return false;
        }
        goto retry;
}