dasd_alias.c

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/*
 * PAV alias management for the DASD ECKD discipline
 *
 * Copyright IBM Corp. 2007
 * Author(s): Stefan Weinhuber <[email protected]>
 */

#define KMSG_COMPONENT "dasd-eckd"

#include <linux/list.h>
#include <linux/slab.h>
#include <asm/ebcdic.h>
#include "dasd_int.h"
#include "dasd_eckd.h"

#ifdef PRINTK_HEADER
#undef PRINTK_HEADER
#endif              /* PRINTK_HEADER */
#define PRINTK_HEADER "dasd(eckd):"


/*
 * General concept of alias management:
 * - PAV and DASD alias management is specific to the eckd discipline.
 * - A device is connected to an lcu as long as the device exists.
 *   dasd_alias_make_device_known_to_lcu will be called wenn the
 *   device is checked by the eckd discipline and
 *   dasd_alias_disconnect_device_from_lcu will be called
 *   before the device is deleted.
 * - The dasd_alias_add_device / dasd_alias_remove_device
 *   functions mark the point when a device is 'ready for service'.
 * - A summary unit check is a rare occasion, but it is mandatory to
 *   support it. It requires some complex recovery actions before the
 *   devices can be used again (see dasd_alias_handle_summary_unit_check).
 * - dasd_alias_get_start_dev will find an alias device that can be used
 *   instead of the base device and does some (very simple) load balancing.
 *   This is the function that gets called for each I/O, so when improving
 *   something, this function should get faster or better, the rest has just
 *   to be correct.
 */


static void summary_unit_check_handling_work(struct work_struct *);
static void lcu_update_work(struct work_struct *);
static int _schedule_lcu_update(struct alias_lcu *, struct dasd_device *);

static struct alias_root aliastree = {
    .serverlist = LIST_HEAD_INIT(aliastree.serverlist),
    .lock = __SPIN_LOCK_UNLOCKED(aliastree.lock),
};

static struct alias_server *_find_server(struct dasd_uid *uid)
{
    struct alias_server *pos;
    list_for_each_entry(pos, &aliastree.serverlist, server) {
        if (!strncmp(pos->uid.vendor, uid->vendor,
                 sizeof(uid->vendor))
            && !strncmp(pos->uid.serial, uid->serial,
                sizeof(uid->serial)))
            return pos;
    };
    return NULL;
}

static struct alias_lcu *_find_lcu(struct alias_server *server,
                   struct dasd_uid *uid)
{
    struct alias_lcu *pos;
    list_for_each_entry(pos, &server->lculist, lcu) {
        if (pos->uid.ssid == uid->ssid)
            return pos;
    };
    return NULL;
}

static struct alias_pav_group *_find_group(struct alias_lcu *lcu,
                       struct dasd_uid *uid)
{
    struct alias_pav_group *pos;
    __u8 search_unit_addr;

    /* for hyper pav there is only one group */
    if (lcu->pav == HYPER_PAV) {
        if (list_empty(&lcu->grouplist))
            return NULL;
        else
            return list_first_entry(&lcu->grouplist,
                        struct alias_pav_group, group);
    }

    /* for base pav we have to find the group that matches the base */
    if (uid->type == UA_BASE_DEVICE)
        search_unit_addr = uid->real_unit_addr;
    else
        search_unit_addr = uid->base_unit_addr;
    list_for_each_entry(pos, &lcu->grouplist, group) {
        if (pos->uid.base_unit_addr == search_unit_addr &&
            !strncmp(pos->uid.vduit, uid->vduit, sizeof(uid->vduit)))
            return pos;
    };
    return NULL;
}

static struct alias_server *_allocate_server(struct dasd_uid *uid)
{
    struct alias_server *server;

    server = kzalloc(sizeof(*server), GFP_KERNEL);
    if (!server)
        return ERR_PTR(-ENOMEM);
    memcpy(server->uid.vendor, uid->vendor, sizeof(uid->vendor));
    memcpy(server->uid.serial, uid->serial, sizeof(uid->serial));
    INIT_LIST_HEAD(&server->server);
    INIT_LIST_HEAD(&server->lculist);
    return server;
}

static void _free_server(struct alias_server *server)
{
    kfree(server);
}

static struct alias_lcu *_allocate_lcu(struct dasd_uid *uid)
{
    struct alias_lcu *lcu;

    lcu = kzalloc(sizeof(*lcu), GFP_KERNEL);
    if (!lcu)
        return ERR_PTR(-ENOMEM);
    lcu->uac = kzalloc(sizeof(*(lcu->uac)), GFP_KERNEL | GFP_DMA);
    if (!lcu->uac)
        goto out_err1;
    lcu->rsu_cqr = kzalloc(sizeof(*lcu->rsu_cqr), GFP_KERNEL | GFP_DMA);
    if (!lcu->rsu_cqr)
        goto out_err2;
    lcu->rsu_cqr->cpaddr = kzalloc(sizeof(struct ccw1),
                       GFP_KERNEL | GFP_DMA);
    if (!lcu->rsu_cqr->cpaddr)
        goto out_err3;
    lcu->rsu_cqr->data = kzalloc(16, GFP_KERNEL | GFP_DMA);
    if (!lcu->rsu_cqr->data)
        goto out_err4;

    memcpy(lcu->uid.vendor, uid->vendor, sizeof(uid->vendor));
    memcpy(lcu->uid.serial, uid->serial, sizeof(uid->serial));
    lcu->uid.ssid = uid->ssid;
    lcu->pav = NO_PAV;
    lcu->flags = NEED_UAC_UPDATE | UPDATE_PENDING;
    INIT_LIST_HEAD(&lcu->lcu);
    INIT_LIST_HEAD(&lcu->inactive_devices);
    INIT_LIST_HEAD(&lcu->active_devices);
    INIT_LIST_HEAD(&lcu->grouplist);
    INIT_WORK(&lcu->suc_data.worker, summary_unit_check_handling_work);
    INIT_DELAYED_WORK(&lcu->ruac_data.dwork, lcu_update_work);
    spin_lock_init(&lcu->lock);
    init_completion(&lcu->lcu_setup);
    return lcu;

out_err4:
    kfree(lcu->rsu_cqr->cpaddr);
out_err3:
    kfree(lcu->rsu_cqr);
out_err2:
    kfree(lcu->uac);
out_err1:
    kfree(lcu);
    return ERR_PTR(-ENOMEM);
}

static void _free_lcu(struct alias_lcu *lcu)
{
    kfree(lcu->rsu_cqr->data);
    kfree(lcu->rsu_cqr->cpaddr);
    kfree(lcu->rsu_cqr);
    kfree(lcu->uac);
    kfree(lcu);
}

/*
 * This is the function that will allocate all the server and lcu data,
 * so this function must be called first for a new device.
 * If the return value is 1, the lcu was already known before, if it
 * is 0, this is a new lcu.
 * Negative return code indicates that something went wrong (e.g. -ENOMEM)
 */
int dasd_alias_make_device_known_to_lcu(struct dasd_device *device)
{
    struct dasd_eckd_private *private;
    unsigned long flags;
    struct alias_server *server, *newserver;
    struct alias_lcu *lcu, *newlcu;
    struct dasd_uid uid;

    private = (struct dasd_eckd_private *) device->private;

    device->discipline->get_uid(device, &uid);
    spin_lock_irqsave(&aliastree.lock, flags);
    server = _find_server(&uid);
    if (!server) {
        spin_unlock_irqrestore(&aliastree.lock, flags);
        newserver = _allocate_server(&uid);
        if (IS_ERR(newserver))
            return PTR_ERR(newserver);
        spin_lock_irqsave(&aliastree.lock, flags);
        server = _find_server(&uid);
        if (!server) {
            list_add(&newserver->server, &aliastree.serverlist);
            server = newserver;
        } else {
            /* someone was faster */
            _free_server(newserver);
        }
    }

    lcu = _find_lcu(server, &uid);
    if (!lcu) {
        spin_unlock_irqrestore(&aliastree.lock, flags);
        newlcu = _allocate_lcu(&uid);
        if (IS_ERR(newlcu))
            return PTR_ERR(newlcu);
        spin_lock_irqsave(&aliastree.lock, flags);
        lcu = _find_lcu(server, &uid);
        if (!lcu) {
            list_add(&newlcu->lcu, &server->lculist);
            lcu = newlcu;
        } else {
            /* someone was faster */
            _free_lcu(newlcu);
        }
    }
    spin_lock(&lcu->lock);
    list_add(&device->alias_list, &lcu->inactive_devices);
    private->lcu = lcu;
    spin_unlock(&lcu->lock);
    spin_unlock_irqrestore(&aliastree.lock, flags);

    return 0;
}

/*
 * This function removes a device from the scope of alias management.
 * The complicated part is to make sure that it is not in use by
 * any of the workers. If necessary cancel the work.
 */
void dasd_alias_disconnect_device_from_lcu(struct dasd_device *device)
{
    struct dasd_eckd_private *private;
    unsigned long flags;
    struct alias_lcu *lcu;
    struct alias_server *server;
    int was_pending;
    struct dasd_uid uid;

    private = (struct dasd_eckd_private *) device->private;
    lcu = private->lcu;
    /* nothing to do if already disconnected */
    if (!lcu)
        return;
    device->discipline->get_uid(device, &uid);
    spin_lock_irqsave(&lcu->lock, flags);
    list_del_init(&device->alias_list);
    /* make sure that the workers don't use this device */
    if (device == lcu->suc_data.device) {
        spin_unlock_irqrestore(&lcu->lock, flags);
        cancel_work_sync(&lcu->suc_data.worker);
        spin_lock_irqsave(&lcu->lock, flags);
        if (device == lcu->suc_data.device)
            lcu->suc_data.device = NULL;
    }
    was_pending = 0;
    if (device == lcu->ruac_data.device) {
        spin_unlock_irqrestore(&lcu->lock, flags);
        was_pending = 1;
        cancel_delayed_work_sync(&lcu->ruac_data.dwork);
        spin_lock_irqsave(&lcu->lock, flags);
        if (device == lcu->ruac_data.device)
            lcu->ruac_data.device = NULL;
    }
    private->lcu = NULL;
    spin_unlock_irqrestore(&lcu->lock, flags);

    spin_lock_irqsave(&aliastree.lock, flags);
    spin_lock(&lcu->lock);
    if (list_empty(&lcu->grouplist) &&
        list_empty(&lcu->active_devices) &&
        list_empty(&lcu->inactive_devices)) {
        list_del(&lcu->lcu);
        spin_unlock(&lcu->lock);
        _free_lcu(lcu);
        lcu = NULL;
    } else {
        if (was_pending)
            _schedule_lcu_update(lcu, NULL);
        spin_unlock(&lcu->lock);
    }
    server = _find_server(&uid);
    if (server && list_empty(&server->lculist)) {
        list_del(&server->server);
        _free_server(server);
    }
    spin_unlock_irqrestore(&aliastree.lock, flags);
}

/*
 * This function assumes that the unit address configuration stored
 * in the lcu is up to date and will update the device uid before
 * adding it to a pav group.
 */

static int _add_device_to_lcu(struct alias_lcu *lcu,
                  struct dasd_device *device,
                  struct dasd_device *pos)
{

    struct dasd_eckd_private *private;
    struct alias_pav_group *group;
    struct dasd_uid uid;
    unsigned long flags;

    private = (struct dasd_eckd_private *) device->private;

    /* only lock if not already locked */
    if (device != pos)
        spin_lock_irqsave_nested(get_ccwdev_lock(device->cdev), flags,
                     CDEV_NESTED_SECOND);
    private->uid.type = lcu->uac->unit[private->uid.real_unit_addr].ua_type;
    private->uid.base_unit_addr =
        lcu->uac->unit[private->uid.real_unit_addr].base_ua;
    uid = private->uid;

    if (device != pos)
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);

    /* if we have no PAV anyway, we don't need to bother with PAV groups */
    if (lcu->pav == NO_PAV) {
        list_move(&device->alias_list, &lcu->active_devices);
        return 0;
    }

    group = _find_group(lcu, &uid);
    if (!group) {
        group = kzalloc(sizeof(*group), GFP_ATOMIC);
        if (!group)
            return -ENOMEM;
        memcpy(group->uid.vendor, uid.vendor, sizeof(uid.vendor));
        memcpy(group->uid.serial, uid.serial, sizeof(uid.serial));
        group->uid.ssid = uid.ssid;
        if (uid.type == UA_BASE_DEVICE)
            group->uid.base_unit_addr = uid.real_unit_addr;
        else
            group->uid.base_unit_addr = uid.base_unit_addr;
        memcpy(group->uid.vduit, uid.vduit, sizeof(uid.vduit));
        INIT_LIST_HEAD(&group->group);
        INIT_LIST_HEAD(&group->baselist);
        INIT_LIST_HEAD(&group->aliaslist);
        list_add(&group->group, &lcu->grouplist);
    }
    if (uid.type == UA_BASE_DEVICE)
        list_move(&device->alias_list, &group->baselist);
    else
        list_move(&device->alias_list, &group->aliaslist);
    private->pavgroup = group;
    return 0;
};

static void _remove_device_from_lcu(struct alias_lcu *lcu,
                    struct dasd_device *device)
{
    struct dasd_eckd_private *private;
    struct alias_pav_group *group;

    private = (struct dasd_eckd_private *) device->private;
    list_move(&device->alias_list, &lcu->inactive_devices);
    group = private->pavgroup;
    if (!group)
        return;
    private->pavgroup = NULL;
    if (list_empty(&group->baselist) && list_empty(&group->aliaslist)) {
        list_del(&group->group);
        kfree(group);
        return;
    }
    if (group->next == device)
        group->next = NULL;
};

static int
suborder_not_supported(struct dasd_ccw_req *cqr)
{
    char *sense;
    char reason;
    char msg_format;
    char msg_no;

    sense = dasd_get_sense(&cqr->irb);
    if (!sense)
        return 0;

    reason = sense[0];
    msg_format = (sense[7] & 0xF0);
    msg_no = (sense[7] & 0x0F);

    /* command reject, Format 0 MSG 4 - invalid parameter */
    if ((reason == 0x80) && (msg_format == 0x00) && (msg_no == 0x04))
        return 1;

    return 0;
}

static int read_unit_address_configuration(struct dasd_device *device,
                       struct alias_lcu *lcu)
{
    struct dasd_psf_prssd_data *prssdp;
    struct dasd_ccw_req *cqr;
    struct ccw1 *ccw;
    int rc;
    unsigned long flags;

    cqr = dasd_kmalloc_request(DASD_ECKD_MAGIC, 1 /* PSF */ + 1 /* RSSD */,
                   (sizeof(struct dasd_psf_prssd_data)),
                   device);
    if (IS_ERR(cqr))
        return PTR_ERR(cqr);
    cqr->startdev = device;
    cqr->memdev = device;
    clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
    cqr->retries = 10;
    cqr->expires = 20 * HZ;

    /* Prepare for Read Subsystem Data */
    prssdp = (struct dasd_psf_prssd_data *) cqr->data;
    memset(prssdp, 0, sizeof(struct dasd_psf_prssd_data));
    prssdp->order = PSF_ORDER_PRSSD;
    prssdp->suborder = 0x0e;    /* Read unit address configuration */
    /* all other bytes of prssdp must be zero */

    ccw = cqr->cpaddr;
    ccw->cmd_code = DASD_ECKD_CCW_PSF;
    ccw->count = sizeof(struct dasd_psf_prssd_data);
    ccw->flags |= CCW_FLAG_CC;
    ccw->cda = (__u32)(addr_t) prssdp;

    /* Read Subsystem Data - feature codes */
    memset(lcu->uac, 0, sizeof(*(lcu->uac)));

    ccw++;
    ccw->cmd_code = DASD_ECKD_CCW_RSSD;
    ccw->count = sizeof(*(lcu->uac));
    ccw->cda = (__u32)(addr_t) lcu->uac;

    cqr->buildclk = get_clock();
    cqr->status = DASD_CQR_FILLED;

    /* need to unset flag here to detect race with summary unit check */
    spin_lock_irqsave(&lcu->lock, flags);
    lcu->flags &= ~NEED_UAC_UPDATE;
    spin_unlock_irqrestore(&lcu->lock, flags);

    do {
        rc = dasd_sleep_on(cqr);
        if (rc && suborder_not_supported(cqr))
            return -EOPNOTSUPP;
    } while (rc && (cqr->retries > 0));
    if (rc) {
        spin_lock_irqsave(&lcu->lock, flags);
        lcu->flags |= NEED_UAC_UPDATE;
        spin_unlock_irqrestore(&lcu->lock, flags);
    }
    dasd_kfree_request(cqr, cqr->memdev);
    return rc;
}

static int _lcu_update(struct dasd_device *refdev, struct alias_lcu *lcu)
{
    unsigned long flags;
    struct alias_pav_group *pavgroup, *tempgroup;
    struct dasd_device *device, *tempdev;
    int i, rc;
    struct dasd_eckd_private *private;

    spin_lock_irqsave(&lcu->lock, flags);
    list_for_each_entry_safe(pavgroup, tempgroup, &lcu->grouplist, group) {
        list_for_each_entry_safe(device, tempdev, &pavgroup->baselist,
                     alias_list) {
            list_move(&device->alias_list, &lcu->active_devices);
            private = (struct dasd_eckd_private *) device->private;
            private->pavgroup = NULL;
        }
        list_for_each_entry_safe(device, tempdev, &pavgroup->aliaslist,
                     alias_list) {
            list_move(&device->alias_list, &lcu->active_devices);
            private = (struct dasd_eckd_private *) device->private;
            private->pavgroup = NULL;
        }
        list_del(&pavgroup->group);
        kfree(pavgroup);
    }
    spin_unlock_irqrestore(&lcu->lock, flags);

    rc = read_unit_address_configuration(refdev, lcu);
    if (rc)
        return rc;

    /* need to take cdev lock before lcu lock */
    spin_lock_irqsave_nested(get_ccwdev_lock(refdev->cdev), flags,
                 CDEV_NESTED_FIRST);
    spin_lock(&lcu->lock);
    lcu->pav = NO_PAV;
    for (i = 0; i < MAX_DEVICES_PER_LCU; ++i) {
        switch (lcu->uac->unit[i].ua_type) {
        case UA_BASE_PAV_ALIAS:
            lcu->pav = BASE_PAV;
            break;
        case UA_HYPER_PAV_ALIAS:
            lcu->pav = HYPER_PAV;
            break;
        }
        if (lcu->pav != NO_PAV)
            break;
    }

    list_for_each_entry_safe(device, tempdev, &lcu->active_devices,
                 alias_list) {
        _add_device_to_lcu(lcu, device, refdev);
    }
    spin_unlock(&lcu->lock);
    spin_unlock_irqrestore(get_ccwdev_lock(refdev->cdev), flags);
    return 0;
}

static void lcu_update_work(struct work_struct *work)
{
    struct alias_lcu *lcu;
    struct read_uac_work_data *ruac_data;
    struct dasd_device *device;
    unsigned long flags;
    int rc;

    ruac_data = container_of(work, struct read_uac_work_data, dwork.work);
    lcu = container_of(ruac_data, struct alias_lcu, ruac_data);
    device = ruac_data->device;
    rc = _lcu_update(device, lcu);
    /*
     * Need to check flags again, as there could have been another
     * prepare_update or a new device a new device while we were still
     * processing the data
     */
    spin_lock_irqsave(&lcu->lock, flags);
    if ((rc && (rc != -EOPNOTSUPP)) || (lcu->flags & NEED_UAC_UPDATE)) {
        DBF_DEV_EVENT(DBF_WARNING, device, "could not update"
                " alias data in lcu (rc = %d), retry later", rc);
        schedule_delayed_work(&lcu->ruac_data.dwork, 30*HZ);
    } else {
        lcu->ruac_data.device = NULL;
        lcu->flags &= ~UPDATE_PENDING;
    }
    spin_unlock_irqrestore(&lcu->lock, flags);
}

static int _schedule_lcu_update(struct alias_lcu *lcu,
                struct dasd_device *device)
{
    struct dasd_device *usedev = NULL;
    struct alias_pav_group *group;

    lcu->flags |= NEED_UAC_UPDATE;
    if (lcu->ruac_data.device) {
        /* already scheduled or running */
        return 0;
    }
    if (device && !list_empty(&device->alias_list))
        usedev = device;

    if (!usedev && !list_empty(&lcu->grouplist)) {
        group = list_first_entry(&lcu->grouplist,
                     struct alias_pav_group, group);
        if (!list_empty(&group->baselist))
            usedev = list_first_entry(&group->baselist,
                          struct dasd_device,
                          alias_list);
        else if (!list_empty(&group->aliaslist))
            usedev = list_first_entry(&group->aliaslist,
                          struct dasd_device,
                          alias_list);
    }
    if (!usedev && !list_empty(&lcu->active_devices)) {
        usedev = list_first_entry(&lcu->active_devices,
                      struct dasd_device, alias_list);
    }
    /*
     * if we haven't found a proper device yet, give up for now, the next
     * device that will be set active will trigger an lcu update
     */
    if (!usedev)
        return -EINVAL;
    lcu->ruac_data.device = usedev;
    schedule_delayed_work(&lcu->ruac_data.dwork, 0);
    return 0;
}

int dasd_alias_add_device(struct dasd_device *device)
{
    struct dasd_eckd_private *private;
    struct alias_lcu *lcu;
    unsigned long flags;
    int rc;

    private = (struct dasd_eckd_private *) device->private;
    lcu = private->lcu;
    rc = 0;

    /* need to take cdev lock before lcu lock */
    spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
    spin_lock(&lcu->lock);
    if (!(lcu->flags & UPDATE_PENDING)) {
        rc = _add_device_to_lcu(lcu, device, device);
        if (rc)
            lcu->flags |= UPDATE_PENDING;
    }
    if (lcu->flags & UPDATE_PENDING) {
        list_move(&device->alias_list, &lcu->active_devices);
        _schedule_lcu_update(lcu, device);
    }
    spin_unlock(&lcu->lock);
    spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
    return rc;
}

int dasd_alias_update_add_device(struct dasd_device *device)
{
    struct dasd_eckd_private *private;
    private = (struct dasd_eckd_private *) device->private;
    private->lcu->flags |= UPDATE_PENDING;
    return dasd_alias_add_device(device);
}

int dasd_alias_remove_device(struct dasd_device *device)
{
    struct dasd_eckd_private *private;
    struct alias_lcu *lcu;
    unsigned long flags;

    private = (struct dasd_eckd_private *) device->private;
    lcu = private->lcu;
    /* nothing to do if already removed */
    if (!lcu)
        return 0;
    spin_lock_irqsave(&lcu->lock, flags);
    _remove_device_from_lcu(lcu, device);
    spin_unlock_irqrestore(&lcu->lock, flags);
    return 0;
}

struct dasd_device *dasd_alias_get_start_dev(struct dasd_device *base_device)
{

    struct dasd_device *alias_device;
    struct alias_pav_group *group;
    struct alias_lcu *lcu;
    struct dasd_eckd_private *private, *alias_priv;
    unsigned long flags;

    private = (struct dasd_eckd_private *) base_device->private;
    group = private->pavgroup;
    lcu = private->lcu;
    if (!group || !lcu)
        return NULL;
    if (lcu->pav == NO_PAV ||
        lcu->flags & (NEED_UAC_UPDATE | UPDATE_PENDING))
        return NULL;
    if (unlikely(!(private->features.feature[8] & 0x01))) {
        /*
         * PAV enabled but prefix not, very unlikely
         * seems to be a lost pathgroup
         * use base device to do IO
         */
        DBF_DEV_EVENT(DBF_ERR, base_device, "%s",
                  "Prefix not enabled with PAV enabled\n");
        return NULL;
    }

    spin_lock_irqsave(&lcu->lock, flags);
    alias_device = group->next;
    if (!alias_device) {
        if (list_empty(&group->aliaslist)) {
            spin_unlock_irqrestore(&lcu->lock, flags);
            return NULL;
        } else {
            alias_device = list_first_entry(&group->aliaslist,
                            struct dasd_device,
                            alias_list);
        }
    }
    if (list_is_last(&alias_device->alias_list, &group->aliaslist))
        group->next = list_first_entry(&group->aliaslist,
                           struct dasd_device, alias_list);
    else
        group->next = list_first_entry(&alias_device->alias_list,
                           struct dasd_device, alias_list);
    spin_unlock_irqrestore(&lcu->lock, flags);
    alias_priv = (struct dasd_eckd_private *) alias_device->private;
    if ((alias_priv->count < private->count) && !alias_device->stopped)
        return alias_device;
    else
        return NULL;
}

/*
 * Summary unit check handling depends on the way alias devices
 * are handled so it is done here rather then in dasd_eckd.c
 */
static int reset_summary_unit_check(struct alias_lcu *lcu,
                    struct dasd_device *device,
                    char reason)
{
    struct dasd_ccw_req *cqr;
    int rc = 0;
    struct ccw1 *ccw;

    cqr = lcu->rsu_cqr;
    strncpy((char *) &cqr->magic, "ECKD", 4);
    ASCEBC((char *) &cqr->magic, 4);
    ccw = cqr->cpaddr;
    ccw->cmd_code = DASD_ECKD_CCW_RSCK;
    ccw->flags = 0 ;
    ccw->count = 16;
    ccw->cda = (__u32)(addr_t) cqr->data;
    ((char *)cqr->data)[0] = reason;

    clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
    cqr->retries = 255; /* set retry counter to enable basic ERP */
    cqr->startdev = device;
    cqr->memdev = device;
    cqr->block = NULL;
    cqr->expires = 5 * HZ;
    cqr->buildclk = get_clock();
    cqr->status = DASD_CQR_FILLED;

    rc = dasd_sleep_on_immediatly(cqr);
    return rc;
}

static void _restart_all_base_devices_on_lcu(struct alias_lcu *lcu)
{
    struct alias_pav_group *pavgroup;
    struct dasd_device *device;
    struct dasd_eckd_private *private;
    unsigned long flags;

    /* active and inactive list can contain alias as well as base devices */
    list_for_each_entry(device, &lcu->active_devices, alias_list) {
        private = (struct dasd_eckd_private *) device->private;
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        if (private->uid.type != UA_BASE_DEVICE) {
            spin_unlock_irqrestore(get_ccwdev_lock(device->cdev),
                           flags);
            continue;
        }
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
        dasd_schedule_block_bh(device->block);
        dasd_schedule_device_bh(device);
    }
    list_for_each_entry(device, &lcu->inactive_devices, alias_list) {
        private = (struct dasd_eckd_private *) device->private;
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        if (private->uid.type != UA_BASE_DEVICE) {
            spin_unlock_irqrestore(get_ccwdev_lock(device->cdev),
                           flags);
            continue;
        }
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
        dasd_schedule_block_bh(device->block);
        dasd_schedule_device_bh(device);
    }
    list_for_each_entry(pavgroup, &lcu->grouplist, group) {
        list_for_each_entry(device, &pavgroup->baselist, alias_list) {
            dasd_schedule_block_bh(device->block);
            dasd_schedule_device_bh(device);
        }
    }
}

static void flush_all_alias_devices_on_lcu(struct alias_lcu *lcu)
{
    struct alias_pav_group *pavgroup;
    struct dasd_device *device, *temp;
    struct dasd_eckd_private *private;
    int rc;
    unsigned long flags;
    LIST_HEAD(active);

    /*
     * Problem here ist that dasd_flush_device_queue may wait
     * for termination of a request to complete. We can't keep
     * the lcu lock during that time, so we must assume that
     * the lists may have changed.
     * Idea: first gather all active alias devices in a separate list,
     * then flush the first element of this list unlocked, and afterwards
     * check if it is still on the list before moving it to the
     * active_devices list.
     */

    spin_lock_irqsave(&lcu->lock, flags);
    list_for_each_entry_safe(device, temp, &lcu->active_devices,
                 alias_list) {
        private = (struct dasd_eckd_private *) device->private;
        if (private->uid.type == UA_BASE_DEVICE)
            continue;
        list_move(&device->alias_list, &active);
    }

    list_for_each_entry(pavgroup, &lcu->grouplist, group) {
        list_splice_init(&pavgroup->aliaslist, &active);
    }
    while (!list_empty(&active)) {
        device = list_first_entry(&active, struct dasd_device,
                      alias_list);
        spin_unlock_irqrestore(&lcu->lock, flags);
        rc = dasd_flush_device_queue(device);
        spin_lock_irqsave(&lcu->lock, flags);
        /*
         * only move device around if it wasn't moved away while we
         * were waiting for the flush
         */
        if (device == list_first_entry(&active,
                           struct dasd_device, alias_list))
            list_move(&device->alias_list, &lcu->active_devices);
    }
    spin_unlock_irqrestore(&lcu->lock, flags);
}

static void __stop_device_on_lcu(struct dasd_device *device,
                 struct dasd_device *pos)
{
    /* If pos == device then device is already locked! */
    if (pos == device) {
        dasd_device_set_stop_bits(pos, DASD_STOPPED_SU);
        return;
    }
    spin_lock(get_ccwdev_lock(pos->cdev));
    dasd_device_set_stop_bits(pos, DASD_STOPPED_SU);
    spin_unlock(get_ccwdev_lock(pos->cdev));
}

/*
 * This function is called in interrupt context, so the
 * cdev lock for device is already locked!
 */
static void _stop_all_devices_on_lcu(struct alias_lcu *lcu,
                     struct dasd_device *device)
{
    struct alias_pav_group *pavgroup;
    struct dasd_device *pos;

    list_for_each_entry(pos, &lcu->active_devices, alias_list)
        __stop_device_on_lcu(device, pos);
    list_for_each_entry(pos, &lcu->inactive_devices, alias_list)
        __stop_device_on_lcu(device, pos);
    list_for_each_entry(pavgroup, &lcu->grouplist, group) {
        list_for_each_entry(pos, &pavgroup->baselist, alias_list)
            __stop_device_on_lcu(device, pos);
        list_for_each_entry(pos, &pavgroup->aliaslist, alias_list)
            __stop_device_on_lcu(device, pos);
    }
}

static void _unstop_all_devices_on_lcu(struct alias_lcu *lcu)
{
    struct alias_pav_group *pavgroup;
    struct dasd_device *device;
    unsigned long flags;

    list_for_each_entry(device, &lcu->active_devices, alias_list) {
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        dasd_device_remove_stop_bits(device, DASD_STOPPED_SU);
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
    }

    list_for_each_entry(device, &lcu->inactive_devices, alias_list) {
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        dasd_device_remove_stop_bits(device, DASD_STOPPED_SU);
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
    }

    list_for_each_entry(pavgroup, &lcu->grouplist, group) {
        list_for_each_entry(device, &pavgroup->baselist, alias_list) {
            spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
            dasd_device_remove_stop_bits(device, DASD_STOPPED_SU);
            spin_unlock_irqrestore(get_ccwdev_lock(device->cdev),
                           flags);
        }
        list_for_each_entry(device, &pavgroup->aliaslist, alias_list) {
            spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
            dasd_device_remove_stop_bits(device, DASD_STOPPED_SU);
            spin_unlock_irqrestore(get_ccwdev_lock(device->cdev),
                           flags);
        }
    }
}

static void summary_unit_check_handling_work(struct work_struct *work)
{
    struct alias_lcu *lcu;
    struct summary_unit_check_work_data *suc_data;
    unsigned long flags;
    struct dasd_device *device;

    suc_data = container_of(work, struct summary_unit_check_work_data,
                worker);
    lcu = container_of(suc_data, struct alias_lcu, suc_data);
    device = suc_data->device;

    /* 1. flush alias devices */
    flush_all_alias_devices_on_lcu(lcu);

    /* 2. reset summary unit check */
    spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
    dasd_device_remove_stop_bits(device,
                     (DASD_STOPPED_SU | DASD_STOPPED_PENDING));
    spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
    reset_summary_unit_check(lcu, device, suc_data->reason);

    spin_lock_irqsave(&lcu->lock, flags);
    _unstop_all_devices_on_lcu(lcu);
    _restart_all_base_devices_on_lcu(lcu);
    /* 3. read new alias configuration */
    _schedule_lcu_update(lcu, device);
    lcu->suc_data.device = NULL;
    spin_unlock_irqrestore(&lcu->lock, flags);
}

/*
 * note: this will be called from int handler context (cdev locked)
 */
void dasd_alias_handle_summary_unit_check(struct dasd_device *device,
                      struct irb *irb)
{
    struct alias_lcu *lcu;
    char reason;
    struct dasd_eckd_private *private;
    char *sense;

    private = (struct dasd_eckd_private *) device->private;

    sense = dasd_get_sense(irb);
    if (sense) {
        reason = sense[8];
        DBF_DEV_EVENT(DBF_NOTICE, device, "%s %x",
                "eckd handle summary unit check: reason", reason);
    } else {
        DBF_DEV_EVENT(DBF_WARNING, device, "%s",
                "eckd handle summary unit check:"
                " no reason code available");
        return;
    }

    lcu = private->lcu;
    if (!lcu) {
        DBF_DEV_EVENT(DBF_WARNING, device, "%s",
                "device not ready to handle summary"
                " unit check (no lcu structure)");
        return;
    }
    spin_lock(&lcu->lock);
    _stop_all_devices_on_lcu(lcu, device);
    /* prepare for lcu_update */
    private->lcu->flags |= NEED_UAC_UPDATE | UPDATE_PENDING;
    /* If this device is about to be removed just return and wait for
     * the next interrupt on a different device
     */
    if (list_empty(&device->alias_list)) {
        DBF_DEV_EVENT(DBF_WARNING, device, "%s",
                "device is in offline processing,"
                " don't do summary unit check handling");
        spin_unlock(&lcu->lock);
        return;
    }
    if (lcu->suc_data.device) {
        /* already scheduled or running */
        DBF_DEV_EVENT(DBF_WARNING, device, "%s",
                "previous instance of summary unit check worker"
                " still pending");
        spin_unlock(&lcu->lock);
        return ;
    }
    lcu->suc_data.reason = reason;
    lcu->suc_data.device = device;
    spin_unlock(&lcu->lock);
    schedule_work(&lcu->suc_data.worker);
};