// 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 unsigned afs_server_update_delay = 30;   /* Time till VLDB recheck in secs */
static atomic_t afs_server_debug_id;

static void afs_inc_servers_outstanding(struct afs_net *net)
{
        atomic_inc(&net->servers_outstanding);
}

static void afs_dec_servers_outstanding(struct afs_net *net)
{
        if (atomic_dec_and_test(&net->servers_outstanding))
                wake_up_var(&net->servers_outstanding);
}

/*
 * Find a server by one of its addresses.
 */
struct afs_server *afs_find_server(struct afs_net *net,
                                   const struct sockaddr_rxrpc *srx)
{
        const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
        const struct afs_addr_list *alist;
        struct afs_server *server = NULL;
        unsigned int i;
        bool ipv6 = true;
        int seq = 0, diff;

        if (srx->transport.sin6.sin6_addr.s6_addr32[0] == 0 ||
            srx->transport.sin6.sin6_addr.s6_addr32[1] == 0 ||
            srx->transport.sin6.sin6_addr.s6_addr32[2] == htonl(0xffff))
                ipv6 = false;

        rcu_read_lock();

        do {
                if (server)
                        afs_put_server(net, server, afs_server_trace_put_find_rsq);
                server = NULL;
                read_seqbegin_or_lock(&net->fs_addr_lock, &seq);

                if (ipv6) {
                        hlist_for_each_entry_rcu(server, &net->fs_addresses6, addr6_link) {
                                alist = rcu_dereference(server->addresses);
                                for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
                                        b = &alist->addrs[i].transport.sin6;
                                        diff = ((u16 __force)a->sin6_port -
                                                (u16 __force)b->sin6_port);
                                        if (diff == 0)
                                                diff = memcmp(&a->sin6_addr,
                                                              &b->sin6_addr,
                                                              sizeof(struct in6_addr));
                                        if (diff == 0)
                                                goto found;
                                }
                        }
                } else {
                        hlist_for_each_entry_rcu(server, &net->fs_addresses4, addr4_link) {
                                alist = rcu_dereference(server->addresses);
                                for (i = 0; i < alist->nr_ipv4; i++) {
                                        b = &alist->addrs[i].transport.sin6;
                                        diff = ((u16 __force)a->sin6_port -
                                                (u16 __force)b->sin6_port);
                                        if (diff == 0)
                                                diff = ((u32 __force)a->sin6_addr.s6_addr32[3] -
                                                        (u32 __force)b->sin6_addr.s6_addr32[3]);
                                        if (diff == 0)
                                                goto found;
                                }
                        }
                }

                server = NULL;
        found:
                if (server && !atomic_inc_not_zero(&server->usage))
                        server = NULL;

        } while (need_seqretry(&net->fs_addr_lock, seq));

        done_seqretry(&net->fs_addr_lock, seq);

        rcu_read_unlock();
        return server;
}

/*
 * Look up a server by its UUID
 */
struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
{
        struct afs_server *server = NULL;
        struct rb_node *p;
        int diff, seq = 0;

        _enter("%pU", uuid);

        do {
                /* Unfortunately, rbtree walking doesn't give reliable results
                 * under just the RCU read lock, so we have to check for
                 * changes.
                 */
                if (server)
                        afs_put_server(net, server, afs_server_trace_put_uuid_rsq);
                server = NULL;

                read_seqbegin_or_lock(&net->fs_lock, &seq);

                p = net->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 {
                                afs_get_server(server, afs_server_trace_get_by_uuid);
                                break;
                        }

                        server = NULL;
                }
        } while (need_seqretry(&net->fs_lock, seq));

        done_seqretry(&net->fs_lock, seq);

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

/*
 * Install a server record in the namespace tree
 */
static struct afs_server *afs_install_server(struct afs_net *net,
                                             struct afs_server *candidate)
{
        const struct afs_addr_list *alist;
        struct afs_server *server;
        struct rb_node **pp, *p;
        int ret = -EEXIST, diff;

        _enter("%p", candidate);

        write_seqlock(&net->fs_lock);

        /* Firstly install the server in the UUID lookup tree */
        pp = &net->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;
        rb_link_node(&server->uuid_rb, p, pp);
        rb_insert_color(&server->uuid_rb, &net->fs_servers);
        hlist_add_head_rcu(&server->proc_link, &net->fs_proc);

        write_seqlock(&net->fs_addr_lock);
        alist = rcu_dereference_protected(server->addresses,
                                          lockdep_is_held(&net->fs_addr_lock.lock));

        /* Secondly, if the server has any IPv4 and/or IPv6 addresses, install
         * it in the IPv4 and/or IPv6 reverse-map lists.
         *
         * TODO: For speed we want to use something other than a flat list
         * here; even sorting the list in terms of lowest address would help a
         * bit, but anything we might want to do gets messy and memory
         * intensive.
         */
        if (alist->nr_ipv4 > 0)
                hlist_add_head_rcu(&server->addr4_link, &net->fs_addresses4);
        if (alist->nr_addrs > alist->nr_ipv4)
                hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);

        write_sequnlock(&net->fs_addr_lock);
        ret = 0;

exists:
        afs_get_server(server, afs_server_trace_get_install);
        write_sequnlock(&net->fs_lock);
        return server;
}

/*
 * allocate a new server record
 */
static struct afs_server *afs_alloc_server(struct afs_net *net,
                                           const uuid_t *uuid,
                                           struct afs_addr_list *alist)
{
        struct afs_server *server;

        _enter("");

        server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
        if (!server)
                goto enomem;

        atomic_set(&server->usage, 1);
        server->debug_id = atomic_inc_return(&afs_server_debug_id);
        RCU_INIT_POINTER(server->addresses, alist);
        server->addr_version = alist->version;
        server->uuid = *uuid;
        server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
        rwlock_init(&server->fs_lock);
        INIT_HLIST_HEAD(&server->cb_volumes);
        rwlock_init(&server->cb_break_lock);
        init_waitqueue_head(&server->probe_wq);
        spin_lock_init(&server->probe_lock);

        afs_inc_servers_outstanding(net);
        trace_afs_server(server, 1, afs_server_trace_alloc);
        _leave(" = %p", server);
        return server;

enomem:
        _leave(" = NULL [nomem]");
        return NULL;
}

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

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

                ret = afs_end_vlserver_operation(&vc);
        }

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

/*
 * Get or create a fileserver record.
 */
struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
                                     const uuid_t *uuid)
{
        struct afs_addr_list *alist;
        struct afs_server *server, *candidate;

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

        server = afs_find_server_by_uuid(cell->net, uuid);
        if (server)
                return server;

        alist = afs_vl_lookup_addrs(cell, key, uuid);
        if (IS_ERR(alist))
                return ERR_CAST(alist);

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

        server = afs_install_server(cell->net, candidate);
        if (server != candidate) {
                afs_put_addrlist(alist);
                kfree(candidate);
        }

        _leave(" = %p{%d}", server, atomic_read(&server->usage));
        return server;
}

/*
 * Set the server timer to fire after a given delay, assuming it's not already
 * set for an earlier time.
 */
static void afs_set_server_timer(struct afs_net *net, time64_t delay)
{
        if (net->live) {
                afs_inc_servers_outstanding(net);
                if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
                        afs_dec_servers_outstanding(net);
        }
}

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

        _enter("");
        if (!queue_work(afs_wq, &net->fs_manager))
                afs_dec_servers_outstanding(net);
}

/*
 * Get a reference on a server object.
 */
struct afs_server *afs_get_server(struct afs_server *server,
                                  enum afs_server_trace reason)
{
        unsigned int u = atomic_inc_return(&server->usage);

        trace_afs_server(server, u, 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 usage;

        if (!server)
                return;

        server->put_time = ktime_get_real_seconds();

        usage = atomic_dec_return(&server->usage);

        trace_afs_server(server, usage, reason);

        if (likely(usage > 0))
                return;

        afs_set_server_timer(net, afs_server_gc_delay);
}

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

        trace_afs_server(server, atomic_read(&server->usage),
                         afs_server_trace_free);
        afs_put_addrlist(rcu_access_pointer(server->addresses));
        kfree(server);
}

/*
 * destroy a dead server
 */
static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
{
        struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
        struct afs_addr_cursor ac = {
                .alist  = alist,
                .index  = alist->preferred,
                .error  = 0,
        };

        trace_afs_server(server, atomic_read(&server->usage),
                         afs_server_trace_give_up_cb);

        if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
                afs_fs_give_up_all_callbacks(net, server, &ac, NULL);

        wait_var_event(&server->probe_outstanding,
                       atomic_read(&server->probe_outstanding) == 0);

        trace_afs_server(server, atomic_read(&server->usage),
                         afs_server_trace_destroy);
        call_rcu(&server->rcu, afs_server_rcu);
        afs_dec_servers_outstanding(net);
}

/*
 * Garbage collect any expired servers.
 */
static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
{
        struct afs_server *server;
        bool deleted;
        int usage;

        while ((server = gc_list)) {
                gc_list = server->gc_next;

                write_seqlock(&net->fs_lock);
                usage = 1;
                deleted = atomic_try_cmpxchg(&server->usage, &usage, 0);
                trace_afs_server(server, usage, afs_server_trace_gc);
                if (deleted) {
                        rb_erase(&server->uuid_rb, &net->fs_servers);
                        hlist_del_rcu(&server->proc_link);
                }
                write_sequnlock(&net->fs_lock);

                if (deleted) {
                        write_seqlock(&net->fs_addr_lock);
                        if (!hlist_unhashed(&server->addr4_link))
                                hlist_del_rcu(&server->addr4_link);
                        if (!hlist_unhashed(&server->addr6_link))
                                hlist_del_rcu(&server->addr6_link);
                        write_sequnlock(&net->fs_addr_lock);
                        afs_destroy_server(net, server);
                }
        }
}

/*
 * Manage the records of servers known to be within a network namespace.  This
 * includes garbage collecting unused servers.
 *
 * Note also that we were given an increment on net->servers_outstanding by
 * whoever queued us that we need to deal with before returning.
 */
void afs_manage_servers(struct work_struct *work)
{
        struct afs_net *net = container_of(work, struct afs_net, fs_manager);
        struct afs_server *gc_list = NULL;
        struct rb_node *cursor;
        time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
        bool purging = !net->live;

        _enter("");

        /* Trawl the server list looking for servers that have expired from
         * lack of use.
         */
        read_seqlock_excl(&net->fs_lock);

        for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
                struct afs_server *server =
                        rb_entry(cursor, struct afs_server, uuid_rb);
                int usage = atomic_read(&server->usage);

                _debug("manage %pU %u", &server->uuid, usage);

                ASSERTCMP(usage, >=, 1);
                ASSERTIFCMP(purging, usage, ==, 1);

                if (usage == 1) {
                        time64_t expire_at = server->put_time;

                        if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
                            !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
                                expire_at += afs_server_gc_delay;
                        if (purging || expire_at <= now) {
                                server->gc_next = gc_list;
                                gc_list = server;
                        } else if (expire_at < next_manage) {
                                next_manage = expire_at;
                        }
                }
        }

        read_sequnlock_excl(&net->fs_lock);

        /* Update the timer on the way out.  We have to pass an increment on
         * servers_outstanding in the namespace that we are in to the timer or
         * the work scheduler.
         */
        if (!purging && next_manage < TIME64_MAX) {
                now = ktime_get_real_seconds();

                if (next_manage - now <= 0) {
                        if (queue_work(afs_wq, &net->fs_manager))
                                afs_inc_servers_outstanding(net);
                } else {
                        afs_set_server_timer(net, next_manage - now);
                }
        }

        afs_gc_servers(net, gc_list);

        afs_dec_servers_outstanding(net);
        _leave(" [%d]", atomic_read(&net->servers_outstanding));
}

static void afs_queue_server_manager(struct afs_net *net)
{
        afs_inc_servers_outstanding(net);
        if (!queue_work(afs_wq, &net->fs_manager))
                afs_dec_servers_outstanding(net);
}

/*
 * Purge list of servers.
 */
void afs_purge_servers(struct afs_net *net)
{
        _enter("");

        if (del_timer_sync(&net->fs_timer))
                atomic_dec(&net->servers_outstanding);

        afs_queue_server_manager(net);

        _debug("wait");
        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_fs_cursor *fc, struct afs_server *server)
{
        struct afs_addr_list *alist, *discard;

        _enter("");

        trace_afs_server(server, atomic_read(&server->usage), afs_server_trace_update);

        alist = afs_vl_lookup_addrs(fc->vnode->volume->cell, fc->key,
                                    &server->uuid);
        if (IS_ERR(alist)) {
                if ((PTR_ERR(alist) == -ERESTARTSYS ||
                     PTR_ERR(alist) == -EINTR) &&
                    !(fc->flags & AFS_FS_CURSOR_INTR) &&
                    server->addresses) {
                        _leave(" = t [intr]");
                        return true;
                }
                fc->error = PTR_ERR(alist);
                _leave(" = f [%d]", fc->error);
                return false;
        }

        discard = alist;
        if (server->addr_version != alist->version) {
                write_lock(&server->fs_lock);
                discard = rcu_dereference_protected(server->addresses,
                                                    lockdep_is_held(&server->fs_lock));
                rcu_assign_pointer(server->addresses, alist);
                server->addr_version = alist->version;
                write_unlock(&server->fs_lock);
        }

        server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
        afs_put_addrlist(discard);
        _leave(" = t");
        return true;
}

/*
 * See if a server's address list needs updating.
 */
bool afs_check_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
{
        time64_t now = ktime_get_real_seconds();
        long diff;
        bool success;
        int ret, retries = 0;

        _enter("");

        ASSERT(server);

retry:
        diff = READ_ONCE(server->update_at) - now;
        if (diff > 0) {
                _leave(" = t [not now %ld]", diff);
                return true;
        }

        if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
                success = afs_update_server_record(fc, server);
                clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
                wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
                _leave(" = %d", success);
                return success;
        }

        ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
                          TASK_INTERRUPTIBLE);
        if (ret == -ERESTARTSYS) {
                if (!(fc->flags & AFS_FS_CURSOR_INTR) && server->addresses) {
                        _leave(" = t [intr]");
                        return true;
                }
                fc->error = ret;
                _leave(" = f [intr]");
                return false;
        }

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