// 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 struct afs_server *afs_maybe_use_server(struct afs_server *,
                                               enum afs_server_trace);
static void __afs_put_server(struct afs_net *, struct afs_server *);

/*
 * 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 afs_addr_list *alist;
        struct afs_server *server = NULL;
        unsigned int i;
        int seq = 0, diff;

        rcu_read_lock();

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

                if (srx->transport.family == AF_INET6) {
                        const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
                        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 {
                        const struct sockaddr_in *a = &srx->transport.sin, *b;
                        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.sin;
                                        diff = ((u16 __force)a->sin_port -
                                                (u16 __force)b->sin_port);
                                        if (diff == 0)
                                                diff = ((u32 __force)a->sin_addr.s_addr -
                                                        (u32 __force)b->sin_addr.s_addr);
                                        if (diff == 0)
                                                goto found;
                                }
                        }
                }

                server = NULL;
                continue;
        found:
                server = afs_maybe_use_server(server, afs_server_trace_get_by_addr);

        } 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 and mark it active.
 */
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_unuse_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_use_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.  If there's a clash, we stick
 * it into a list anchored on whichever afs_server struct is actually in the
 * tree.
 */
static struct afs_server *afs_install_server(struct afs_cell *cell,
                                             struct afs_server *candidate)
{
        const struct afs_addr_list *alist;
        struct afs_server *server, *next;
        struct afs_net *net = cell->net;
        struct rb_node **pp, *p;
        int 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 {
                        if (server->cell == cell)
                                goto exists;

                        /* We have the same UUID representing servers in
                         * different cells.  Append the new server to the list.
                         */
                        for (;;) {
                                next = rcu_dereference_protected(
                                        server->uuid_next,
                                        lockdep_is_held(&net->fs_lock.lock));
                                if (!next)
                                        break;
                                server = next;
                        }
                        rcu_assign_pointer(server->uuid_next, candidate);
                        candidate->uuid_prev = server;
                        server = candidate;
                        goto added_dup;
                }
        }

        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);

added_dup:
        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);

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

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

        _enter("");

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

        atomic_set(&server->ref, 1);
        atomic_set(&server->active, 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;
        rwlock_init(&server->fs_lock);
        init_waitqueue_head(&server->probe_wq);
        INIT_LIST_HEAD(&server->probe_link);
        spin_lock_init(&server->probe_lock);
        server->cell = cell;
        server->rtt = UINT_MAX;

        afs_inc_servers_outstanding(net);
        trace_afs_server(server, 1, 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, u32 addr_version)
{
        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) {
                if (server->addr_version != addr_version)
                        set_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
                return server;
        }

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

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

        server = afs_install_server(cell, candidate);
        if (server != candidate) {
                afs_put_addrlist(alist);
                kfree(candidate);
        } else {
                /* Immediately dispatch an asynchronous probe to each interface
                 * on the fileserver.  This will make sure the repeat-probing
                 * service is started.
                 */
                afs_fs_probe_fileserver(cell->net, server, key, true);
        }

        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->ref);

        trace_afs_server(server, u, atomic_read(&server->active), reason);
        return server;
}

/*
 * Try to get a reference on a server object.
 */
static struct afs_server *afs_maybe_use_server(struct afs_server *server,
                                               enum afs_server_trace reason)
{
        unsigned int r = atomic_fetch_add_unless(&server->ref, 1, 0);
        unsigned int a;

        if (r == 0)
                return NULL;

        a = atomic_inc_return(&server->active);
        trace_afs_server(server, r, a, reason);
        return server;
}

/*
 * Get an active count on a server object.
 */
struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_trace reason)
{
        unsigned int r = atomic_inc_return(&server->ref);
        unsigned int a = atomic_inc_return(&server->active);

        trace_afs_server(server, r, 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 usage;

        if (!server)
                return;

        usage = atomic_dec_return(&server->ref);
        trace_afs_server(server, usage, atomic_read(&server->active), reason);
        if (unlikely(usage == 0))
                __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) {
                unsigned int active = atomic_dec_return(&server->active);

                if (active == 0)
                        afs_set_server_timer(net, afs_server_gc_delay);
                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) {
                server->unuse_time = ktime_get_real_seconds();
                afs_unuse_server_notime(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, atomic_read(&server->ref),
                         atomic_read(&server->active), afs_server_trace_free);
        afs_put_addrlist(rcu_access_pointer(server->addresses));
        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_addr_list *alist = rcu_access_pointer(server->addresses);
        struct afs_addr_cursor ac = {
                .alist  = alist,
                .index  = alist->preferred,
                .error  = 0,
        };

        afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
}

/*
 * destroy a dead server
 */
static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
{
        if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
                afs_give_up_callbacks(net, server);

        afs_put_server(net, server, afs_server_trace_destroy);
}

/*
 * Garbage collect any expired servers.
 */
static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
{
        struct afs_server *server, *next, *prev;
        int active;

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

                write_seqlock(&net->fs_lock);

                active = atomic_read(&server->active);
                if (active == 0) {
                        trace_afs_server(server, atomic_read(&server->ref),
                                         active, afs_server_trace_gc);
                        next = rcu_dereference_protected(
                                server->uuid_next, lockdep_is_held(&net->fs_lock.lock));
                        prev = server->uuid_prev;
                        if (!prev) {
                                /* The one at the front is in the tree */
                                if (!next) {
                                        rb_erase(&server->uuid_rb, &net->fs_servers);
                                } else {
                                        rb_replace_node_rcu(&server->uuid_rb,
                                                            &next->uuid_rb,
                                                            &net->fs_servers);
                                        next->uuid_prev = NULL;
                                }
                        } else {
                                /* This server is not at the front */
                                rcu_assign_pointer(prev->uuid_next, next);
                                if (next)
                                        next->uuid_prev = prev;
                        }

                        list_del(&server->probe_link);
                        hlist_del_rcu(&server->proc_link);
                        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_lock);

                if (active == 0)
                        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 active = atomic_read(&server->active);

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

                if (purging) {
                        trace_afs_server(server, atomic_read(&server->ref),
                                         active, afs_server_trace_purging);
                        if (active != 0)
                                pr_notice("Can't purge s=%08x\n", server->debug_id);
                }

                if (active == 0) {
                        time64_t expire_at = server->unuse_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))
                afs_dec_servers_outstanding(net);

        afs_queue_server_manager(net);

        _debug("wait");
        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 afs_addr_list *alist, *discard;

        _enter("");

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

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

        afs_put_addrlist(discard);
        _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)
{
        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);
                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) {
                op->error = ret;
                _leave(" = f [intr]");
                return false;
        }

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