vlocation.c

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/* AFS volume location management
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * 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/slab.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();
        queue_delayed_work(afs_wq, &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);
            mod_delayed_work(afs_wq, &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);
    mod_delayed_work(afs_vlocation_update_worker, &afs_vlocation_update, 0);
    destroy_workqueue(afs_vlocation_update_worker);

    mod_delayed_work(afs_wq, &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);
}