// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS cell and server record management
 *
 * Copyright (C) 2002, 2017 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <linux/key.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/sched.h>
#include <linux/inet.h>
#include <linux/namei.h>
#include <keys/rxrpc-type.h>
#include "internal.h"

static unsigned __read_mostly afs_cell_gc_delay = 10;
static unsigned __read_mostly afs_cell_min_ttl = 10 * 60;
static unsigned __read_mostly afs_cell_max_ttl = 24 * 60 * 60;
static atomic_t cell_debug_id;

static void afs_cell_timer(struct timer_list *timer);
static void afs_destroy_cell_work(struct work_struct *work);
static void afs_manage_cell_work(struct work_struct *work);

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

static void afs_set_cell_state(struct afs_cell *cell, enum afs_cell_state state)
{
        smp_store_release(&cell->state, state); /* Commit cell changes before state */
        smp_wmb(); /* Set cell state before task state */
        wake_up_var(&cell->state);
}

/*
 * Look up and get an activation reference on a cell record.  The caller must
 * hold net->cells_lock at least read-locked.
 */
static struct afs_cell *afs_find_cell_locked(struct afs_net *net,
                                             const char *name, unsigned int namesz,
                                             enum afs_cell_trace reason)
{
        struct afs_cell *cell = NULL;
        struct rb_node *p;
        int n;

        _enter("%*.*s", namesz, namesz, name);

        if (name && namesz == 0)
                return ERR_PTR(-EINVAL);
        if (namesz > AFS_MAXCELLNAME)
                return ERR_PTR(-ENAMETOOLONG);

        if (!name) {
                cell = rcu_dereference_protected(net->ws_cell,
                                                 lockdep_is_held(&net->cells_lock));
                if (!cell)
                        return ERR_PTR(-EDESTADDRREQ);
                goto found;
        }

        p = net->cells.rb_node;
        while (p) {
                cell = rb_entry(p, struct afs_cell, net_node);

                n = strncasecmp(cell->name, name,
                                min_t(size_t, cell->name_len, namesz));
                if (n == 0)
                        n = cell->name_len - namesz;
                if (n < 0)
                        p = p->rb_left;
                else if (n > 0)
                        p = p->rb_right;
                else
                        goto found;
        }

        return ERR_PTR(-ENOENT);

found:
        return afs_use_cell(cell, reason);
}

/*
 * Look up and get an activation reference on a cell record.
 */
struct afs_cell *afs_find_cell(struct afs_net *net,
                               const char *name, unsigned int namesz,
                               enum afs_cell_trace reason)
{
        struct afs_cell *cell;

        down_read(&net->cells_lock);
        cell = afs_find_cell_locked(net, name, namesz, reason);
        up_read(&net->cells_lock);
        return cell;
}

/*
 * Set up a cell record and fill in its name, VL server address list and
 * allocate an anonymous key
 */
static struct afs_cell *afs_alloc_cell(struct afs_net *net,
                                       const char *name, unsigned int namelen,
                                       const char *addresses)
{
        struct afs_vlserver_list *vllist = NULL;
        struct afs_cell *cell;
        int i, ret;

        ASSERT(name);
        if (namelen == 0)
                return ERR_PTR(-EINVAL);
        if (namelen > AFS_MAXCELLNAME) {
                _leave(" = -ENAMETOOLONG");
                return ERR_PTR(-ENAMETOOLONG);
        }

        /* Prohibit cell names that contain unprintable chars, '/' and '@' or
         * that begin with a dot.  This also precludes "@cell".
         */
        if (name[0] == '.')
                return ERR_PTR(-EINVAL);
        for (i = 0; i < namelen; i++) {
                char ch = name[i];
                if (!isprint(ch) || ch == '/' || ch == '@')
                        return ERR_PTR(-EINVAL);
        }

        _enter("%*.*s,%s", namelen, namelen, name, addresses);

        cell = kzalloc_obj(struct afs_cell);
        if (!cell) {
                _leave(" = -ENOMEM");
                return ERR_PTR(-ENOMEM);
        }

        /* Allocate the cell name and the key name in one go. */
        cell->name = kmalloc(1 + namelen + 1 +
                             4 + namelen + 1, GFP_KERNEL);
        if (!cell->name) {
                kfree(cell);
                return ERR_PTR(-ENOMEM);
        }

        cell->name[0] = '.';
        cell->name++;
        cell->name_len = namelen;
        for (i = 0; i < namelen; i++)
                cell->name[i] = tolower(name[i]);
        cell->name[i++] = 0;

        cell->key_desc = cell->name + i;
        memcpy(cell->key_desc, "afs@", 4);
        memcpy(cell->key_desc + 4, cell->name, cell->name_len + 1);

        cell->net = net;
        refcount_set(&cell->ref, 1);
        atomic_set(&cell->active, 0);
        INIT_WORK(&cell->destroyer, afs_destroy_cell_work);
        INIT_WORK(&cell->manager, afs_manage_cell_work);
        timer_setup(&cell->management_timer, afs_cell_timer, 0);
        init_rwsem(&cell->vs_lock);
        cell->volumes = RB_ROOT;
        INIT_HLIST_HEAD(&cell->proc_volumes);
        seqlock_init(&cell->volume_lock);
        cell->fs_servers = RB_ROOT;
        init_rwsem(&cell->fs_lock);
        rwlock_init(&cell->vl_servers_lock);
        cell->flags = (1 << AFS_CELL_FL_CHECK_ALIAS);

        /* Provide a VL server list, filling it in if we were given a list of
         * addresses to use.
         */
        if (addresses) {
                vllist = afs_parse_text_addrs(net,
                                              addresses, strlen(addresses), ':',
                                              VL_SERVICE, AFS_VL_PORT);
                if (IS_ERR(vllist)) {
                        ret = PTR_ERR(vllist);
                        vllist = NULL;
                        goto parse_failed;
                }

                vllist->source = DNS_RECORD_FROM_CONFIG;
                vllist->status = DNS_LOOKUP_NOT_DONE;
                cell->dns_expiry = TIME64_MAX;
        } else {
                ret = -ENOMEM;
                vllist = afs_alloc_vlserver_list(0);
                if (!vllist)
                        goto error;
                vllist->source = DNS_RECORD_UNAVAILABLE;
                vllist->status = DNS_LOOKUP_NOT_DONE;
                cell->dns_expiry = ktime_get_real_seconds();
        }

        rcu_assign_pointer(cell->vl_servers, vllist);

        cell->dns_source = vllist->source;
        cell->dns_status = vllist->status;
        smp_store_release(&cell->dns_lookup_count, 1); /* vs source/status */
        atomic_inc(&net->cells_outstanding);
        ret = idr_alloc_cyclic(&net->cells_dyn_ino, cell,
                               2, INT_MAX / 2, GFP_KERNEL);
        if (ret < 0)
                goto error;
        cell->dynroot_ino = ret;
        cell->debug_id = atomic_inc_return(&cell_debug_id);

        trace_afs_cell(cell->debug_id, 1, 0, afs_cell_trace_alloc);

        _leave(" = %p", cell);
        return cell;

parse_failed:
        if (ret == -EINVAL)
                printk(KERN_ERR "kAFS: bad VL server IP address\n");
error:
        afs_put_vlserverlist(cell->net, vllist);
        kfree(cell->name - 1);
        kfree(cell);
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * afs_lookup_cell - Look up or create a cell record.
 * @net:        The network namespace
 * @name:       The name of the cell.
 * @namesz:     The strlen of the cell name.
 * @vllist:     A colon/comma separated list of numeric IP addresses or NULL.
 * @reason:     The reason we're doing the lookup
 * @trace:      The reason to be logged if the lookup is successful.
 *
 * Look up a cell record by name and query the DNS for VL server addresses if
 * needed.  Note that that actual DNS query is punted off to the manager thread
 * so that this function can return immediately if interrupted whilst allowing
 * cell records to be shared even if not yet fully constructed.
 */
struct afs_cell *afs_lookup_cell(struct afs_net *net,
                                 const char *name, unsigned int namesz,
                                 const char *vllist,
                                 enum afs_lookup_cell_for reason,
                                 enum afs_cell_trace trace)
{
        struct afs_cell *cell, *candidate, *cursor;
        struct rb_node *parent, **pp;
        enum afs_cell_state state;
        int ret, n;

        _enter("%s,%s,%u", name, vllist, reason);

        if (reason != AFS_LOOKUP_CELL_PRELOAD) {
                cell = afs_find_cell(net, name, namesz, trace);
                if (!IS_ERR(cell)) {
                        if (reason == AFS_LOOKUP_CELL_DYNROOT)
                                goto no_wait;
                        if (cell->state == AFS_CELL_SETTING_UP ||
                            cell->state == AFS_CELL_UNLOOKED)
                                goto lookup_cell;
                        goto wait_for_cell;
                }
        }

        /* Assume we're probably going to create a cell and preallocate and
         * mostly set up a candidate record.  We can then use this to stash the
         * name, the net namespace and VL server addresses.
         *
         * We also want to do this before we hold any locks as it may involve
         * upcalling to userspace to make DNS queries.
         */
        candidate = afs_alloc_cell(net, name, namesz, vllist);
        if (IS_ERR(candidate)) {
                _leave(" = %ld", PTR_ERR(candidate));
                return candidate;
        }

        /* Find the insertion point and check to see if someone else added a
         * cell whilst we were allocating.
         */
        down_write(&net->cells_lock);

        pp = &net->cells.rb_node;
        parent = NULL;
        while (*pp) {
                parent = *pp;
                cursor = rb_entry(parent, struct afs_cell, net_node);

                n = strncasecmp(cursor->name, name,
                                min_t(size_t, cursor->name_len, namesz));
                if (n == 0)
                        n = cursor->name_len - namesz;
                if (n < 0)
                        pp = &(*pp)->rb_left;
                else if (n > 0)
                        pp = &(*pp)->rb_right;
                else
                        goto cell_already_exists;
        }

        cell = candidate;
        candidate = NULL;
        afs_use_cell(cell, trace);
        rb_link_node_rcu(&cell->net_node, parent, pp);
        rb_insert_color(&cell->net_node, &net->cells);
        up_write(&net->cells_lock);

lookup_cell:
        if (reason != AFS_LOOKUP_CELL_PRELOAD &&
            reason != AFS_LOOKUP_CELL_ROOTCELL) {
                set_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags);
                afs_queue_cell(cell, afs_cell_trace_queue_new);
        }

wait_for_cell:
        state = smp_load_acquire(&cell->state); /* vs error */
        switch (state) {
        case AFS_CELL_ACTIVE:
        case AFS_CELL_DEAD:
                break;
        case AFS_CELL_UNLOOKED:
        default:
                if (reason == AFS_LOOKUP_CELL_PRELOAD ||
                    reason == AFS_LOOKUP_CELL_ROOTCELL)
                        break;
                _debug("wait_for_cell");
                afs_see_cell(cell, afs_cell_trace_wait);
                wait_var_event(&cell->state,
                               ({
                                       state = smp_load_acquire(&cell->state); /* vs error */
                                       state == AFS_CELL_ACTIVE || state == AFS_CELL_DEAD;
                               }));
                _debug("waited_for_cell %d %d", cell->state, cell->error);
        }

no_wait:
        /* Check the state obtained from the wait check. */
        state = smp_load_acquire(&cell->state); /* vs error */
        if (state == AFS_CELL_DEAD) {
                ret = cell->error;
                goto error;
        }
        if (state == AFS_CELL_ACTIVE) {
                switch (cell->dns_status) {
                case DNS_LOOKUP_NOT_DONE:
                        if (cell->dns_source == DNS_RECORD_FROM_CONFIG) {
                                ret = 0;
                                break;
                        }
                        fallthrough;
                default:
                        ret = -EIO;
                        goto error;
                case DNS_LOOKUP_GOOD:
                case DNS_LOOKUP_GOOD_WITH_BAD:
                        ret = 0;
                        break;
                case DNS_LOOKUP_GOT_NOT_FOUND:
                        ret = -ENOENT;
                        goto error;
                case DNS_LOOKUP_BAD:
                        ret = -EREMOTEIO;
                        goto error;
                case DNS_LOOKUP_GOT_LOCAL_FAILURE:
                case DNS_LOOKUP_GOT_TEMP_FAILURE:
                case DNS_LOOKUP_GOT_NS_FAILURE:
                        ret = -EDESTADDRREQ;
                        goto error;
                }
        }

        _leave(" = %p [cell]", cell);
        return cell;

cell_already_exists:
        _debug("cell exists");
        cell = cursor;
        if (reason == AFS_LOOKUP_CELL_PRELOAD) {
                ret = -EEXIST;
        } else {
                afs_use_cell(cursor, trace);
                ret = 0;
        }
        up_write(&net->cells_lock);
        if (candidate)
                afs_put_cell(candidate, afs_cell_trace_put_candidate);
        if (ret == 0)
                goto wait_for_cell;
        goto error_noput;
error:
        afs_unuse_cell(cell, afs_cell_trace_unuse_lookup_error);
error_noput:
        _leave(" = %d [error]", ret);
        return ERR_PTR(ret);
}

/*
 * set the root cell information
 * - can be called with a module parameter string
 * - can be called from a write to /proc/fs/afs/rootcell
 */
int afs_cell_init(struct afs_net *net, const char *rootcell)
{
        struct afs_cell *old_root, *new_root;
        const char *cp, *vllist;
        size_t len;

        _enter("");

        if (!rootcell) {
                /* module is loaded with no parameters, or built statically.
                 * - in the future we might initialize cell DB here.
                 */
                _leave(" = 0 [no root]");
                return 0;
        }

        cp = strchr(rootcell, ':');
        if (!cp) {
                _debug("kAFS: no VL server IP addresses specified");
                vllist = NULL;
                len = strlen(rootcell);
        } else {
                vllist = cp + 1;
                len = cp - rootcell;
        }

        if (len == 0 || !rootcell[0] || rootcell[0] == '.' || rootcell[len - 1] == '.')
                return -EINVAL;
        if (memchr(rootcell, '/', len))
                return -EINVAL;
        cp = strstr(rootcell, "..");
        if (cp && cp < rootcell + len)
                return -EINVAL;

        /* allocate a cell record for the root/workstation cell */
        new_root = afs_lookup_cell(net, rootcell, len, vllist,
                                   AFS_LOOKUP_CELL_ROOTCELL,
                                   afs_cell_trace_use_lookup_ws);
        if (IS_ERR(new_root)) {
                _leave(" = %ld", PTR_ERR(new_root));
                return PTR_ERR(new_root);
        }

        if (!test_and_set_bit(AFS_CELL_FL_NO_GC, &new_root->flags))
                afs_use_cell(new_root, afs_cell_trace_use_pin);

        /* install the new cell */
        down_write(&net->cells_lock);
        old_root = rcu_replace_pointer(net->ws_cell, new_root,
                                       lockdep_is_held(&net->cells_lock));
        up_write(&net->cells_lock);

        afs_unuse_cell(old_root, afs_cell_trace_unuse_ws);
        _leave(" = 0");
        return 0;
}

/*
 * Update a cell's VL server address list from the DNS.
 */
static int afs_update_cell(struct afs_cell *cell)
{
        struct afs_vlserver_list *vllist, *old = NULL, *p;
        unsigned int min_ttl = READ_ONCE(afs_cell_min_ttl);
        unsigned int max_ttl = READ_ONCE(afs_cell_max_ttl);
        time64_t now, expiry = 0;
        int ret = 0;

        _enter("%s", cell->name);

        vllist = afs_dns_query(cell, &expiry);
        if (IS_ERR(vllist)) {
                ret = PTR_ERR(vllist);

                _debug("%s: fail %d", cell->name, ret);
                if (ret == -ENOMEM)
                        goto out_wake;

                vllist = afs_alloc_vlserver_list(0);
                if (!vllist) {
                        if (ret >= 0)
                                ret = -ENOMEM;
                        goto out_wake;
                }

                switch (ret) {
                case -ENODATA:
                case -EDESTADDRREQ:
                        vllist->status = DNS_LOOKUP_GOT_NOT_FOUND;
                        break;
                case -EAGAIN:
                case -ECONNREFUSED:
                        vllist->status = DNS_LOOKUP_GOT_TEMP_FAILURE;
                        break;
                default:
                        vllist->status = DNS_LOOKUP_GOT_LOCAL_FAILURE;
                        break;
                }
        }

        _debug("%s: got list %d %d", cell->name, vllist->source, vllist->status);
        cell->dns_status = vllist->status;

        now = ktime_get_real_seconds();
        if (min_ttl > max_ttl)
                max_ttl = min_ttl;
        if (expiry < now + min_ttl)
                expiry = now + min_ttl;
        else if (expiry > now + max_ttl)
                expiry = now + max_ttl;

        _debug("%s: status %d", cell->name, vllist->status);
        if (vllist->source == DNS_RECORD_UNAVAILABLE) {
                switch (vllist->status) {
                case DNS_LOOKUP_GOT_NOT_FOUND:
                        /* The DNS said that the cell does not exist or there
                         * weren't any addresses to be had.
                         */
                        cell->dns_expiry = expiry;
                        break;

                case DNS_LOOKUP_BAD:
                case DNS_LOOKUP_GOT_LOCAL_FAILURE:
                case DNS_LOOKUP_GOT_TEMP_FAILURE:
                case DNS_LOOKUP_GOT_NS_FAILURE:
                default:
                        cell->dns_expiry = now + 10;
                        break;
                }
        } else {
                cell->dns_expiry = expiry;
        }

        /* Replace the VL server list if the new record has servers or the old
         * record doesn't.
         */
        write_lock(&cell->vl_servers_lock);
        p = rcu_dereference_protected(cell->vl_servers, true);
        if (vllist->nr_servers > 0 || p->nr_servers == 0) {
                rcu_assign_pointer(cell->vl_servers, vllist);
                cell->dns_source = vllist->source;
                old = p;
        }
        write_unlock(&cell->vl_servers_lock);
        afs_put_vlserverlist(cell->net, old);

out_wake:
        smp_store_release(&cell->dns_lookup_count,
                          cell->dns_lookup_count + 1); /* vs source/status */
        wake_up_var(&cell->dns_lookup_count);
        _leave(" = %d", ret);
        return ret;
}

/*
 * Destroy a cell record
 */
static void afs_cell_destroy(struct rcu_head *rcu)
{
        struct afs_cell *cell = container_of(rcu, struct afs_cell, rcu);
        struct afs_net *net = cell->net;
        int r;

        _enter("%p{%s}", cell, cell->name);

        r = refcount_read(&cell->ref);
        ASSERTCMP(r, ==, 0);
        trace_afs_cell(cell->debug_id, r, atomic_read(&cell->active), afs_cell_trace_free);

        afs_put_vlserverlist(net, rcu_access_pointer(cell->vl_servers));
        afs_unuse_cell(cell->alias_of, afs_cell_trace_unuse_alias);
        key_put(cell->anonymous_key);
        idr_remove(&net->cells_dyn_ino, cell->dynroot_ino);
        kfree(cell->name - 1);
        kfree(cell);

        afs_dec_cells_outstanding(net);
        _leave(" [destroyed]");
}

static void afs_destroy_cell_work(struct work_struct *work)
{
        struct afs_cell *cell = container_of(work, struct afs_cell, destroyer);

        afs_see_cell(cell, afs_cell_trace_destroy);
        timer_delete_sync(&cell->management_timer);
        cancel_work_sync(&cell->manager);
        call_rcu(&cell->rcu, afs_cell_destroy);
}

/*
 * Get a reference on a cell record.
 */
struct afs_cell *afs_get_cell(struct afs_cell *cell, enum afs_cell_trace reason)
{
        int r;

        __refcount_inc(&cell->ref, &r);
        trace_afs_cell(cell->debug_id, r + 1, atomic_read(&cell->active), reason);
        return cell;
}

/*
 * Drop a reference on a cell record.
 */
void afs_put_cell(struct afs_cell *cell, enum afs_cell_trace reason)
{
        if (cell) {
                unsigned int debug_id = cell->debug_id;
                unsigned int a;
                bool zero;
                int r;

                a = atomic_read(&cell->active);
                zero = __refcount_dec_and_test(&cell->ref, &r);
                trace_afs_cell(debug_id, r - 1, a, reason);
                if (zero) {
                        a = atomic_read(&cell->active);
                        WARN(a != 0, "Cell active count %u > 0\n", a);
                        WARN_ON(!queue_work(afs_wq, &cell->destroyer));
                }
        }
}

/*
 * Note a cell becoming more active.
 */
struct afs_cell *afs_use_cell(struct afs_cell *cell, enum afs_cell_trace reason)
{
        int r, a;

        __refcount_inc(&cell->ref, &r);
        a = atomic_inc_return(&cell->active);
        trace_afs_cell(cell->debug_id, r + 1, a, reason);
        return cell;
}

/*
 * Record a cell becoming less active.  When the active counter reaches 1, it
 * is scheduled for destruction, but may get reactivated.
 */
void afs_unuse_cell(struct afs_cell *cell, enum afs_cell_trace reason)
{
        unsigned int debug_id;
        time64_t now, expire_delay;
        bool zero;
        int r, a;

        if (!cell)
                return;

        _enter("%s", cell->name);

        now = ktime_get_real_seconds();
        cell->last_inactive = now;
        expire_delay = 0;
        if (cell->vl_servers->nr_servers)
                expire_delay = afs_cell_gc_delay;

        debug_id = cell->debug_id;
        a = atomic_dec_return(&cell->active);
        if (!a)
                /* 'cell' may now be garbage collected. */
                afs_set_cell_timer(cell, expire_delay);

        zero = __refcount_dec_and_test(&cell->ref, &r);
        trace_afs_cell(debug_id, r - 1, a, reason);
        if (zero)
                WARN_ON(!queue_work(afs_wq, &cell->destroyer));
}

/*
 * Note that a cell has been seen.
 */
void afs_see_cell(struct afs_cell *cell, enum afs_cell_trace reason)
{
        int r, a;

        r = refcount_read(&cell->ref);
        a = atomic_read(&cell->active);
        trace_afs_cell(cell->debug_id, r, a, reason);
}

/*
 * Queue a cell for management, giving the workqueue a ref to hold.
 */
void afs_queue_cell(struct afs_cell *cell, enum afs_cell_trace reason)
{
        queue_work(afs_wq, &cell->manager);
}

/*
 * Cell-specific management timer.
 */
static void afs_cell_timer(struct timer_list *timer)
{
        struct afs_cell *cell = container_of(timer, struct afs_cell, management_timer);

        afs_see_cell(cell, afs_cell_trace_see_mgmt_timer);
        if (refcount_read(&cell->ref) > 0 && cell->net->live)
                queue_work(afs_wq, &cell->manager);
}

/*
 * Set/reduce the cell timer.
 */
void afs_set_cell_timer(struct afs_cell *cell, unsigned int delay_secs)
{
        timer_reduce(&cell->management_timer, jiffies + delay_secs * HZ);
}

/*
 * Activate a cell.
 */
static int afs_activate_cell(struct afs_net *net, struct afs_cell *cell)
{
        struct hlist_node **p;
        struct afs_cell *pcell;
        int ret;

        ret = afs_proc_cell_setup(cell);
        if (ret < 0)
                return ret;

        mutex_lock(&net->proc_cells_lock);
        for (p = &net->proc_cells.first; *p; p = &(*p)->next) {
                pcell = hlist_entry(*p, struct afs_cell, proc_link);
                if (strcmp(cell->name, pcell->name) < 0)
                        break;
        }

        cell->proc_link.pprev = p;
        cell->proc_link.next = *p;
        rcu_assign_pointer(*p, &cell->proc_link.next);
        if (cell->proc_link.next)
                cell->proc_link.next->pprev = &cell->proc_link.next;

        mutex_unlock(&net->proc_cells_lock);
        return 0;
}

/*
 * Deactivate a cell.
 */
static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
{
        _enter("%s", cell->name);

        afs_proc_cell_remove(cell);

        mutex_lock(&net->proc_cells_lock);
        if (!hlist_unhashed(&cell->proc_link))
                hlist_del_rcu(&cell->proc_link);
        mutex_unlock(&net->proc_cells_lock);

        _leave("");
}

static bool afs_has_cell_expired(struct afs_cell *cell, time64_t *_next_manage)
{
        const struct afs_vlserver_list *vllist;
        time64_t expire_at = cell->last_inactive;
        time64_t now = ktime_get_real_seconds();

        if (atomic_read(&cell->active))
                return false;
        if (!cell->net->live)
                return true;

        vllist = rcu_dereference_protected(cell->vl_servers, true);
        if (vllist && vllist->nr_servers > 0)
                expire_at += afs_cell_gc_delay;

        if (expire_at <= now)
                return true;
        if (expire_at < *_next_manage)
                *_next_manage = expire_at;
        return false;
}

/*
 * Manage a cell record, initialising and destroying it, maintaining its DNS
 * records.
 */
static bool afs_manage_cell(struct afs_cell *cell)
{
        struct afs_net *net = cell->net;
        time64_t next_manage = TIME64_MAX;
        int ret;

        _enter("%s", cell->name);

        _debug("state %u", cell->state);
        switch (cell->state) {
        case AFS_CELL_SETTING_UP:
                goto set_up_cell;
        case AFS_CELL_UNLOOKED:
        case AFS_CELL_ACTIVE:
                goto cell_is_active;
        case AFS_CELL_REMOVING:
                WARN_ON_ONCE(1);
                return false;
        case AFS_CELL_DEAD:
                return false;
        default:
                _debug("bad state %u", cell->state);
                WARN_ON_ONCE(1); /* Unhandled state */
                return false;
        }

set_up_cell:
        ret = afs_activate_cell(net, cell);
        if (ret < 0) {
                cell->error = ret;
                goto remove_cell;
        }

        afs_set_cell_state(cell, AFS_CELL_UNLOOKED);

cell_is_active:
        if (afs_has_cell_expired(cell, &next_manage))
                goto remove_cell;

        if (test_and_clear_bit(AFS_CELL_FL_DO_LOOKUP, &cell->flags)) {
                ret = afs_update_cell(cell);
                if (ret < 0)
                        cell->error = ret;
                if (cell->state == AFS_CELL_UNLOOKED)
                        afs_set_cell_state(cell, AFS_CELL_ACTIVE);
        }

        if (next_manage < TIME64_MAX && cell->net->live) {
                time64_t now = ktime_get_real_seconds();

                if (next_manage - now <= 0)
                        afs_queue_cell(cell, afs_cell_trace_queue_again);
                else
                        afs_set_cell_timer(cell, next_manage - now);
        }
        _leave(" [done %u]", cell->state);
        return false;

remove_cell:
        down_write(&net->cells_lock);

        if (atomic_read(&cell->active)) {
                up_write(&net->cells_lock);
                goto cell_is_active;
        }

        /* Make sure that the expiring server records are going to see the fact
         * that the cell is caput.
         */
        afs_set_cell_state(cell, AFS_CELL_REMOVING);

        afs_deactivate_cell(net, cell);
        afs_purge_servers(cell);

        rb_erase(&cell->net_node, &net->cells);
        afs_see_cell(cell, afs_cell_trace_unuse_delete);
        up_write(&net->cells_lock);

        /* The root volume is pinning the cell */
        afs_put_volume(cell->root_volume, afs_volume_trace_put_cell_root);
        cell->root_volume = NULL;

        afs_set_cell_state(cell, AFS_CELL_DEAD);
        return true;
}

static void afs_manage_cell_work(struct work_struct *work)
{
        struct afs_cell *cell = container_of(work, struct afs_cell, manager);
        bool final_put;

        afs_see_cell(cell, afs_cell_trace_manage);
        final_put = afs_manage_cell(cell);
        afs_see_cell(cell, afs_cell_trace_managed);
        if (final_put)
                afs_put_cell(cell, afs_cell_trace_put_final);
}

/*
 * Purge in-memory cell database.
 */
void afs_cell_purge(struct afs_net *net)
{
        struct afs_cell *ws;
        struct rb_node *cursor;

        _enter("");

        down_write(&net->cells_lock);
        ws = rcu_replace_pointer(net->ws_cell, NULL,
                                 lockdep_is_held(&net->cells_lock));
        up_write(&net->cells_lock);
        afs_unuse_cell(ws, afs_cell_trace_unuse_ws);

        _debug("kick cells");
        down_read(&net->cells_lock);
        for (cursor = rb_first(&net->cells); cursor; cursor = rb_next(cursor)) {
                struct afs_cell *cell = rb_entry(cursor, struct afs_cell, net_node);

                afs_see_cell(cell, afs_cell_trace_purge);

                if (test_and_clear_bit(AFS_CELL_FL_NO_GC, &cell->flags))
                        afs_unuse_cell(cell, afs_cell_trace_unuse_pin);

                afs_queue_cell(cell, afs_cell_trace_queue_purge);
        }
        up_read(&net->cells_lock);

        _debug("wait");
        wait_var_event(&net->cells_outstanding,
                       !atomic_read(&net->cells_outstanding));
        _leave("");
}