/* AFS volume location management
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include "internal.h"

static unsigned afs_vlocation_timeout = 10;     /* volume location timeout in seconds */
static unsigned afs_vlocation_update_timeout = 10 * 60;

static void afs_vlocation_reaper(struct work_struct *);
static void afs_vlocation_updater(struct work_struct *);

static LIST_HEAD(afs_vlocation_updates);
static LIST_HEAD(afs_vlocation_graveyard);
static DEFINE_SPINLOCK(afs_vlocation_updates_lock);
static DEFINE_SPINLOCK(afs_vlocation_graveyard_lock);
static DECLARE_DELAYED_WORK(afs_vlocation_reap, afs_vlocation_reaper);
static DECLARE_DELAYED_WORK(afs_vlocation_update, afs_vlocation_updater);
static struct workqueue_struct *afs_vlocation_update_worker;

/*
 * iterate through the VL servers in a cell until one of them admits knowing
 * about the volume in question
 */
static int afs_vlocation_access_vl_by_name(struct afs_vlocation *vl,
                                           struct key *key,
                                           struct afs_cache_vlocation *vldb)
{
        struct afs_cell *cell = vl->cell;
        struct in_addr addr;
        int count, ret;

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

        down_write(&vl->cell->vl_sem);
        ret = -ENOMEDIUM;
        for (count = cell->vl_naddrs; count > 0; count--) {
                addr = cell->vl_addrs[cell->vl_curr_svix];

                _debug("CellServ[%hu]: %08x", cell->vl_curr_svix, addr.s_addr);

                /* attempt to access the VL server */
                ret = afs_vl_get_entry_by_name(&addr, key, vl->vldb.name, vldb,
                                               &afs_sync_call);
                switch (ret) {
                case 0:
                        goto out;
                case -ENOMEM:
                case -ENONET:
                case -ENETUNREACH:
                case -EHOSTUNREACH:
                case -ECONNREFUSED:
                        if (ret == -ENOMEM || ret == -ENONET)
                                goto out;
                        goto rotate;
                case -ENOMEDIUM:
                case -EKEYREJECTED:
                case -EKEYEXPIRED:
                        goto out;
                default:
                        ret = -EIO;
                        goto rotate;
                }

                /* rotate the server records upon lookup failure */
        rotate:
                cell->vl_curr_svix++;
                cell->vl_curr_svix %= cell->vl_naddrs;
        }

out:
        up_write(&vl->cell->vl_sem);
        _leave(" = %d", ret);
        return ret;
}

/*
 * iterate through the VL servers in a cell until one of them admits knowing
 * about the volume in question
 */
static int afs_vlocation_access_vl_by_id(struct afs_vlocation *vl,
                                         struct key *key,
                                         afs_volid_t volid,
                                         afs_voltype_t voltype,
                                         struct afs_cache_vlocation *vldb)
{
        struct afs_cell *cell = vl->cell;
        struct in_addr addr;
        int count, ret;

        _enter("%s,%x,%d,", cell->name, volid, voltype);

        down_write(&vl->cell->vl_sem);
        ret = -ENOMEDIUM;
        for (count = cell->vl_naddrs; count > 0; count--) {
                addr = cell->vl_addrs[cell->vl_curr_svix];

                _debug("CellServ[%hu]: %08x", cell->vl_curr_svix, addr.s_addr);

                /* attempt to access the VL server */
                ret = afs_vl_get_entry_by_id(&addr, key, volid, voltype, vldb,
                                             &afs_sync_call);
                switch (ret) {
                case 0:
                        goto out;
                case -ENOMEM:
                case -ENONET:
                case -ENETUNREACH:
                case -EHOSTUNREACH:
                case -ECONNREFUSED:
                        if (ret == -ENOMEM || ret == -ENONET)
                                goto out;
                        goto rotate;
                case -EBUSY:
                        vl->upd_busy_cnt++;
                        if (vl->upd_busy_cnt <= 3) {
                                if (vl->upd_busy_cnt > 1) {
                                        /* second+ BUSY - sleep a little bit */
                                        set_current_state(TASK_UNINTERRUPTIBLE);
                                        schedule_timeout(1);
                                        __set_current_state(TASK_RUNNING);
                                }
                                continue;
                        }
                        break;
                case -ENOMEDIUM:
                        vl->upd_rej_cnt++;
                        goto rotate;
                default:
                        ret = -EIO;
                        goto rotate;
                }

                /* rotate the server records upon lookup failure */
        rotate:
                cell->vl_curr_svix++;
                cell->vl_curr_svix %= cell->vl_naddrs;
                vl->upd_busy_cnt = 0;
        }

out:
        if (ret < 0 && vl->upd_rej_cnt > 0) {
                printk(KERN_NOTICE "kAFS:"
                       " Active volume no longer valid '%s'\n",
                       vl->vldb.name);
                vl->valid = 0;
                ret = -ENOMEDIUM;
        }

        up_write(&vl->cell->vl_sem);
        _leave(" = %d", ret);
        return ret;
}

/*
 * allocate a volume location record
 */
static struct afs_vlocation *afs_vlocation_alloc(struct afs_cell *cell,
                                                 const char *name,
                                                 size_t namesz)
{
        struct afs_vlocation *vl;

        vl = kzalloc(sizeof(struct afs_vlocation), GFP_KERNEL);
        if (vl) {
                vl->cell = cell;
                vl->state = AFS_VL_NEW;
                atomic_set(&vl->usage, 1);
                INIT_LIST_HEAD(&vl->link);
                INIT_LIST_HEAD(&vl->grave);
                INIT_LIST_HEAD(&vl->update);
                init_waitqueue_head(&vl->waitq);
                spin_lock_init(&vl->lock);
                memcpy(vl->vldb.name, name, namesz);
        }

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

/*
 * update record if we found it in the cache
 */
static int afs_vlocation_update_record(struct afs_vlocation *vl,
                                       struct key *key,
                                       struct afs_cache_vlocation *vldb)
{
        afs_voltype_t voltype;
        afs_volid_t vid;
        int ret;

        /* try to look up a cached volume in the cell VL databases by ID */
        _debug("Locally Cached: %s %02x { %08x(%x) %08x(%x) %08x(%x) }",
               vl->vldb.name,
               vl->vldb.vidmask,
               ntohl(vl->vldb.servers[0].s_addr),
               vl->vldb.srvtmask[0],
               ntohl(vl->vldb.servers[1].s_addr),
               vl->vldb.srvtmask[1],
               ntohl(vl->vldb.servers[2].s_addr),
               vl->vldb.srvtmask[2]);

        _debug("Vids: %08x %08x %08x",
               vl->vldb.vid[0],
               vl->vldb.vid[1],
               vl->vldb.vid[2]);

        if (vl->vldb.vidmask & AFS_VOL_VTM_RW) {
                vid = vl->vldb.vid[0];
                voltype = AFSVL_RWVOL;
        } else if (vl->vldb.vidmask & AFS_VOL_VTM_RO) {
                vid = vl->vldb.vid[1];
                voltype = AFSVL_ROVOL;
        } else if (vl->vldb.vidmask & AFS_VOL_VTM_BAK) {
                vid = vl->vldb.vid[2];
                voltype = AFSVL_BACKVOL;
        } else {
                BUG();
                vid = 0;
                voltype = 0;
        }

        /* contact the server to make sure the volume is still available
         * - TODO: need to handle disconnected operation here
         */
        ret = afs_vlocation_access_vl_by_id(vl, key, vid, voltype, vldb);
        switch (ret) {
                /* net error */
        default:
                printk(KERN_WARNING "kAFS:"
                       " failed to update volume '%s' (%x) up in '%s': %d\n",
                       vl->vldb.name, vid, vl->cell->name, ret);
                _leave(" = %d", ret);
                return ret;

                /* pulled from local cache into memory */
        case 0:
                _leave(" = 0");
                return 0;

                /* uh oh... looks like the volume got deleted */
        case -ENOMEDIUM:
                printk(KERN_ERR "kAFS:"
                       " volume '%s' (%x) does not exist '%s'\n",
                       vl->vldb.name, vid, vl->cell->name);

                /* TODO: make existing record unavailable */
                _leave(" = %d", ret);
                return ret;
        }
}

/*
 * apply the update to a VL record
 */
static void afs_vlocation_apply_update(struct afs_vlocation *vl,
                                       struct afs_cache_vlocation *vldb)
{
        _debug("Done VL Lookup: %s %02x { %08x(%x) %08x(%x) %08x(%x) }",
               vldb->name, vldb->vidmask,
               ntohl(vldb->servers[0].s_addr), vldb->srvtmask[0],
               ntohl(vldb->servers[1].s_addr), vldb->srvtmask[1],
               ntohl(vldb->servers[2].s_addr), vldb->srvtmask[2]);

        _debug("Vids: %08x %08x %08x",
               vldb->vid[0], vldb->vid[1], vldb->vid[2]);

        if (strcmp(vldb->name, vl->vldb.name) != 0)
                printk(KERN_NOTICE "kAFS:"
                       " name of volume '%s' changed to '%s' on server\n",
                       vl->vldb.name, vldb->name);

        vl->vldb = *vldb;

#ifdef CONFIG_AFS_FSCACHE
        fscache_update_cookie(vl->cache);
#endif
}

/*
 * fill in a volume location record, consulting the cache and the VL server
 * both
 */
static int afs_vlocation_fill_in_record(struct afs_vlocation *vl,
                                        struct key *key)
{
        struct afs_cache_vlocation vldb;
        int ret;

        _enter("");

        ASSERTCMP(vl->valid, ==, 0);

        memset(&vldb, 0, sizeof(vldb));

        /* see if we have an in-cache copy (will set vl->valid if there is) */
#ifdef CONFIG_AFS_FSCACHE
        vl->cache = fscache_acquire_cookie(vl->cell->cache,
                                           &afs_vlocation_cache_index_def, vl);
#endif

        if (vl->valid) {
                /* try to update a known volume in the cell VL databases by
                 * ID as the name may have changed */
                _debug("found in cache");
                ret = afs_vlocation_update_record(vl, key, &vldb);
        } else {
                /* try to look up an unknown volume in the cell VL databases by
                 * name */
                ret = afs_vlocation_access_vl_by_name(vl, key, &vldb);
                if (ret < 0) {
                        printk("kAFS: failed to locate '%s' in cell '%s'\n",
                               vl->vldb.name, vl->cell->name);
                        return ret;
                }
        }

        afs_vlocation_apply_update(vl, &vldb);
        _leave(" = 0");
        return 0;
}

/*
 * queue a vlocation record for updates
 */
static void afs_vlocation_queue_for_updates(struct afs_vlocation *vl)
{
        struct afs_vlocation *xvl;

        /* wait at least 10 minutes before updating... */
        vl->update_at = get_seconds() + afs_vlocation_update_timeout;

        spin_lock(&afs_vlocation_updates_lock);

        if (!list_empty(&afs_vlocation_updates)) {
                /* ... but wait at least 1 second more than the newest record
                 * already queued so that we don't spam the VL server suddenly
                 * with lots of requests
                 */
                xvl = list_entry(afs_vlocation_updates.prev,
                                 struct afs_vlocation, update);
                if (vl->update_at <= xvl->update_at)
                        vl->update_at = xvl->update_at + 1;
        } else {
                queue_delayed_work(afs_vlocation_update_worker,
                                   &afs_vlocation_update,
                                   afs_vlocation_update_timeout * HZ);
        }

        list_add_tail(&vl->update, &afs_vlocation_updates);
        spin_unlock(&afs_vlocation_updates_lock);
}

/*
 * lookup volume location
 * - iterate through the VL servers in a cell until one of them admits knowing
 *   about the volume in question
 * - lookup in the local cache if not able to find on the VL server
 * - insert/update in the local cache if did get a VL response
 */
struct afs_vlocation *afs_vlocation_lookup(struct afs_cell *cell,
                                           struct key *key,
                                           const char *name,
                                           size_t namesz)
{
        struct afs_vlocation *vl;
        int ret;

        _enter("{%s},{%x},%*.*s,%zu",
               cell->name, key_serial(key),
               (int) namesz, (int) namesz, name, namesz);

        if (namesz >= sizeof(vl->vldb.name)) {
                _leave(" = -ENAMETOOLONG");
                return ERR_PTR(-ENAMETOOLONG);
        }

        /* see if we have an in-memory copy first */
        down_write(&cell->vl_sem);
        spin_lock(&cell->vl_lock);
        list_for_each_entry(vl, &cell->vl_list, link) {
                if (vl->vldb.name[namesz] != '\0')
                        continue;
                if (memcmp(vl->vldb.name, name, namesz) == 0)
                        goto found_in_memory;
        }
        spin_unlock(&cell->vl_lock);

        /* not in the cell's in-memory lists - create a new record */
        vl = afs_vlocation_alloc(cell, name, namesz);
        if (!vl) {
                up_write(&cell->vl_sem);
                return ERR_PTR(-ENOMEM);
        }

        afs_get_cell(cell);

        list_add_tail(&vl->link, &cell->vl_list);
        vl->state = AFS_VL_CREATING;
        up_write(&cell->vl_sem);

fill_in_record:
        ret = afs_vlocation_fill_in_record(vl, key);
        if (ret < 0)
                goto error_abandon;
        spin_lock(&vl->lock);
        vl->state = AFS_VL_VALID;
        spin_unlock(&vl->lock);
        wake_up(&vl->waitq);

        /* update volume entry in local cache */
#ifdef CONFIG_AFS_FSCACHE
        fscache_update_cookie(vl->cache);
#endif

        /* schedule for regular updates */
        afs_vlocation_queue_for_updates(vl);
        goto success;

found_in_memory:
        /* found in memory */
        _debug("found in memory");
        atomic_inc(&vl->usage);
        spin_unlock(&cell->vl_lock);
        if (!list_empty(&vl->grave)) {
                spin_lock(&afs_vlocation_graveyard_lock);
                list_del_init(&vl->grave);
                spin_unlock(&afs_vlocation_graveyard_lock);
        }
        up_write(&cell->vl_sem);

        /* see if it was an abandoned record that we might try filling in */
        spin_lock(&vl->lock);
        while (vl->state != AFS_VL_VALID) {
                afs_vlocation_state_t state = vl->state;

                _debug("invalid [state %d]", state);

                if (state == AFS_VL_NEW || state == AFS_VL_NO_VOLUME) {
                        vl->state = AFS_VL_CREATING;
                        spin_unlock(&vl->lock);
                        goto fill_in_record;
                }

                /* must now wait for creation or update by someone else to
                 * complete */
                _debug("wait");

                spin_unlock(&vl->lock);
                ret = wait_event_interruptible(vl->waitq,
                                               vl->state == AFS_VL_NEW ||
                                               vl->state == AFS_VL_VALID ||
                                               vl->state == AFS_VL_NO_VOLUME);
                if (ret < 0)
                        goto error;
                spin_lock(&vl->lock);
        }
        spin_unlock(&vl->lock);

success:
        _leave(" = %p", vl);
        return vl;

error_abandon:
        spin_lock(&vl->lock);
        vl->state = AFS_VL_NEW;
        spin_unlock(&vl->lock);
        wake_up(&vl->waitq);
error:
        ASSERT(vl != NULL);
        afs_put_vlocation(vl);
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * finish using a volume location record
 */
void afs_put_vlocation(struct afs_vlocation *vl)
{
        if (!vl)
                return;

        _enter("%s", vl->vldb.name);

        ASSERTCMP(atomic_read(&vl->usage), >, 0);

        if (likely(!atomic_dec_and_test(&vl->usage))) {
                _leave("");
                return;
        }

        spin_lock(&afs_vlocation_graveyard_lock);
        if (atomic_read(&vl->usage) == 0) {
                _debug("buried");
                list_move_tail(&vl->grave, &afs_vlocation_graveyard);
                vl->time_of_death = get_seconds();
                schedule_delayed_work(&afs_vlocation_reap,
                                      afs_vlocation_timeout * HZ);

                /* suspend updates on this record */
                if (!list_empty(&vl->update)) {
                        spin_lock(&afs_vlocation_updates_lock);
                        list_del_init(&vl->update);
                        spin_unlock(&afs_vlocation_updates_lock);
                }
        }
        spin_unlock(&afs_vlocation_graveyard_lock);
        _leave(" [killed?]");
}

/*
 * destroy a dead volume location record
 */
static void afs_vlocation_destroy(struct afs_vlocation *vl)
{
        _enter("%p", vl);

#ifdef CONFIG_AFS_FSCACHE
        fscache_relinquish_cookie(vl->cache, 0);
#endif
        afs_put_cell(vl->cell);
        kfree(vl);
}

/*
 * reap dead volume location records
 */
static void afs_vlocation_reaper(struct work_struct *work)
{
        LIST_HEAD(corpses);
        struct afs_vlocation *vl;
        unsigned long delay, expiry;
        time_t now;

        _enter("");

        now = get_seconds();
        spin_lock(&afs_vlocation_graveyard_lock);

        while (!list_empty(&afs_vlocation_graveyard)) {
                vl = list_entry(afs_vlocation_graveyard.next,
                                struct afs_vlocation, grave);

                _debug("check %p", vl);

                /* the queue is ordered most dead first */
                expiry = vl->time_of_death + afs_vlocation_timeout;
                if (expiry > now) {
                        delay = (expiry - now) * HZ;
                        _debug("delay %lu", delay);
                        if (!schedule_delayed_work(&afs_vlocation_reap,
                                                   delay)) {
                                cancel_delayed_work(&afs_vlocation_reap);
                                schedule_delayed_work(&afs_vlocation_reap,
                                                      delay);
                        }
                        break;
                }

                spin_lock(&vl->cell->vl_lock);
                if (atomic_read(&vl->usage) > 0) {
                        _debug("no reap");
                        list_del_init(&vl->grave);
                } else {
                        _debug("reap");
                        list_move_tail(&vl->grave, &corpses);
                        list_del_init(&vl->link);
                }
                spin_unlock(&vl->cell->vl_lock);
        }

        spin_unlock(&afs_vlocation_graveyard_lock);

        /* now reap the corpses we've extracted */
        while (!list_empty(&corpses)) {
                vl = list_entry(corpses.next, struct afs_vlocation, grave);
                list_del(&vl->grave);
                afs_vlocation_destroy(vl);
        }

        _leave("");
}

/*
 * initialise the VL update process
 */
int __init afs_vlocation_update_init(void)
{
        afs_vlocation_update_worker =
                create_singlethread_workqueue("kafs_vlupdated");
        return afs_vlocation_update_worker ? 0 : -ENOMEM;
}

/*
 * discard all the volume location records for rmmod
 */
void afs_vlocation_purge(void)
{
        afs_vlocation_timeout = 0;

        spin_lock(&afs_vlocation_updates_lock);
        list_del_init(&afs_vlocation_updates);
        spin_unlock(&afs_vlocation_updates_lock);
        cancel_delayed_work(&afs_vlocation_update);
        queue_delayed_work(afs_vlocation_update_worker,
                           &afs_vlocation_update, 0);
        destroy_workqueue(afs_vlocation_update_worker);

        cancel_delayed_work(&afs_vlocation_reap);
        schedule_delayed_work(&afs_vlocation_reap, 0);
}

/*
 * update a volume location
 */
static void afs_vlocation_updater(struct work_struct *work)
{
        struct afs_cache_vlocation vldb;
        struct afs_vlocation *vl, *xvl;
        time_t now;
        long timeout;
        int ret;

        _enter("");

        now = get_seconds();

        /* find a record to update */
        spin_lock(&afs_vlocation_updates_lock);
        for (;;) {
                if (list_empty(&afs_vlocation_updates)) {
                        spin_unlock(&afs_vlocation_updates_lock);
                        _leave(" [nothing]");
                        return;
                }

                vl = list_entry(afs_vlocation_updates.next,
                                struct afs_vlocation, update);
                if (atomic_read(&vl->usage) > 0)
                        break;
                list_del_init(&vl->update);
        }

        timeout = vl->update_at - now;
        if (timeout > 0) {
                queue_delayed_work(afs_vlocation_update_worker,
                                   &afs_vlocation_update, timeout * HZ);
                spin_unlock(&afs_vlocation_updates_lock);
                _leave(" [nothing]");
                return;
        }

        list_del_init(&vl->update);
        atomic_inc(&vl->usage);
        spin_unlock(&afs_vlocation_updates_lock);

        /* we can now perform the update */
        _debug("update %s", vl->vldb.name);
        vl->state = AFS_VL_UPDATING;
        vl->upd_rej_cnt = 0;
        vl->upd_busy_cnt = 0;

        ret = afs_vlocation_update_record(vl, NULL, &vldb);
        spin_lock(&vl->lock);
        switch (ret) {
        case 0:
                afs_vlocation_apply_update(vl, &vldb);
                vl->state = AFS_VL_VALID;
                break;
        case -ENOMEDIUM:
                vl->state = AFS_VL_VOLUME_DELETED;
                break;
        default:
                vl->state = AFS_VL_UNCERTAIN;
                break;
        }
        spin_unlock(&vl->lock);
        wake_up(&vl->waitq);

        /* and then reschedule */
        _debug("reschedule");
        vl->update_at = get_seconds() + afs_vlocation_update_timeout;

        spin_lock(&afs_vlocation_updates_lock);

        if (!list_empty(&afs_vlocation_updates)) {
                /* next update in 10 minutes, but wait at least 1 second more
                 * than the newest record already queued so that we don't spam
                 * the VL server suddenly with lots of requests
                 */
                xvl = list_entry(afs_vlocation_updates.prev,
                                 struct afs_vlocation, update);
                if (vl->update_at <= xvl->update_at)
                        vl->update_at = xvl->update_at + 1;
                xvl = list_entry(afs_vlocation_updates.next,
                                 struct afs_vlocation, update);
                timeout = xvl->update_at - now;
                if (timeout < 0)
                        timeout = 0;
        } else {
                timeout = afs_vlocation_update_timeout;
        }

        ASSERT(list_empty(&vl->update));

        list_add_tail(&vl->update, &afs_vlocation_updates);

        _debug("timeout %ld", timeout);
        queue_delayed_work(afs_vlocation_update_worker,
                           &afs_vlocation_update, timeout * HZ);
        spin_unlock(&afs_vlocation_updates_lock);
        afs_put_vlocation(vl);
}