mm/hmm.c: remove superfluous RCU protection around radix tree lookup

[linux/fpc-iii.git] / drivers / s390 / char / tape_core.c

// SPDX-License-Identifier: GPL-2.0
/*
 *    basic function of the tape device driver
 *
 *  S390 and zSeries version
 *    Copyright IBM Corp. 2001, 2009
 *    Author(s): Carsten Otte <cotte@de.ibm.com>
 *               Michael Holzheu <holzheu@de.ibm.com>
 *               Tuan Ngo-Anh <ngoanh@de.ibm.com>
 *               Martin Schwidefsky <schwidefsky@de.ibm.com>
 *               Stefan Bader <shbader@de.ibm.com>
 */

#define KMSG_COMPONENT "tape"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/module.h>
#include <linux/init.h>      // for kernel parameters
#include <linux/kmod.h>      // for requesting modules
#include <linux/spinlock.h>  // for locks
#include <linux/vmalloc.h>
#include <linux/list.h>
#include <linux/slab.h>

#include <asm/types.h>       // for variable types

#define TAPE_DBF_AREA   tape_core_dbf

#include "tape.h"
#include "tape_std.h"

#define LONG_BUSY_TIMEOUT 180 /* seconds */

static void __tape_do_irq (struct ccw_device *, unsigned long, struct irb *);
static void tape_delayed_next_request(struct work_struct *);
static void tape_long_busy_timeout(struct timer_list *t);

/*
 * One list to contain all tape devices of all disciplines, so
 * we can assign the devices to minor numbers of the same major
 * The list is protected by the rwlock
 */
static LIST_HEAD(tape_device_list);
static DEFINE_RWLOCK(tape_device_lock);

/*
 * Pointer to debug area.
 */
debug_info_t *TAPE_DBF_AREA = NULL;
EXPORT_SYMBOL(TAPE_DBF_AREA);

/*
 * Printable strings for tape enumerations.
 */
const char *tape_state_verbose[TS_SIZE] =
{
        [TS_UNUSED]   = "UNUSED",
        [TS_IN_USE]   = "IN_USE",
        [TS_BLKUSE]   = "BLKUSE",
        [TS_INIT]     = "INIT  ",
        [TS_NOT_OPER] = "NOT_OP"
};

const char *tape_op_verbose[TO_SIZE] =
{
        [TO_BLOCK] = "BLK",     [TO_BSB] = "BSB",
        [TO_BSF] = "BSF",       [TO_DSE] = "DSE",
        [TO_FSB] = "FSB",       [TO_FSF] = "FSF",
        [TO_LBL] = "LBL",       [TO_NOP] = "NOP",
        [TO_RBA] = "RBA",       [TO_RBI] = "RBI",
        [TO_RFO] = "RFO",       [TO_REW] = "REW",
        [TO_RUN] = "RUN",       [TO_WRI] = "WRI",
        [TO_WTM] = "WTM",       [TO_MSEN] = "MSN",
        [TO_LOAD] = "LOA",      [TO_READ_CONFIG] = "RCF",
        [TO_READ_ATTMSG] = "RAT",
        [TO_DIS] = "DIS",       [TO_ASSIGN] = "ASS",
        [TO_UNASSIGN] = "UAS",  [TO_CRYPT_ON] = "CON",
        [TO_CRYPT_OFF] = "COF", [TO_KEKL_SET] = "KLS",
        [TO_KEKL_QUERY] = "KLQ",[TO_RDC] = "RDC",
};

static int devid_to_int(struct ccw_dev_id *dev_id)
{
        return dev_id->devno + (dev_id->ssid << 16);
}

/*
 * Some channel attached tape specific attributes.
 *
 * FIXME: In the future the first_minor and blocksize attribute should be
 *        replaced by a link to the cdev tree.
 */
static ssize_t
tape_medium_state_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct tape_device *tdev;

        tdev = dev_get_drvdata(dev);
        return scnprintf(buf, PAGE_SIZE, "%i\n", tdev->medium_state);
}

static
DEVICE_ATTR(medium_state, 0444, tape_medium_state_show, NULL);

static ssize_t
tape_first_minor_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct tape_device *tdev;

        tdev = dev_get_drvdata(dev);
        return scnprintf(buf, PAGE_SIZE, "%i\n", tdev->first_minor);
}

static
DEVICE_ATTR(first_minor, 0444, tape_first_minor_show, NULL);

static ssize_t
tape_state_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct tape_device *tdev;

        tdev = dev_get_drvdata(dev);
        return scnprintf(buf, PAGE_SIZE, "%s\n", (tdev->first_minor < 0) ?
                "OFFLINE" : tape_state_verbose[tdev->tape_state]);
}

static
DEVICE_ATTR(state, 0444, tape_state_show, NULL);

static ssize_t
tape_operation_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct tape_device *tdev;
        ssize_t rc;

        tdev = dev_get_drvdata(dev);
        if (tdev->first_minor < 0)
                return scnprintf(buf, PAGE_SIZE, "N/A\n");

        spin_lock_irq(get_ccwdev_lock(tdev->cdev));
        if (list_empty(&tdev->req_queue))
                rc = scnprintf(buf, PAGE_SIZE, "---\n");
        else {
                struct tape_request *req;

                req = list_entry(tdev->req_queue.next, struct tape_request,
                        list);
                rc = scnprintf(buf,PAGE_SIZE, "%s\n", tape_op_verbose[req->op]);
        }
        spin_unlock_irq(get_ccwdev_lock(tdev->cdev));
        return rc;
}

static
DEVICE_ATTR(operation, 0444, tape_operation_show, NULL);

static ssize_t
tape_blocksize_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct tape_device *tdev;

        tdev = dev_get_drvdata(dev);

        return scnprintf(buf, PAGE_SIZE, "%i\n", tdev->char_data.block_size);
}

static
DEVICE_ATTR(blocksize, 0444, tape_blocksize_show, NULL);

static struct attribute *tape_attrs[] = {
        &dev_attr_medium_state.attr,
        &dev_attr_first_minor.attr,
        &dev_attr_state.attr,
        &dev_attr_operation.attr,
        &dev_attr_blocksize.attr,
        NULL
};

static const struct attribute_group tape_attr_group = {
        .attrs = tape_attrs,
};

/*
 * Tape state functions
 */
void
tape_state_set(struct tape_device *device, enum tape_state newstate)
{
        const char *str;

        if (device->tape_state == TS_NOT_OPER) {
                DBF_EVENT(3, "ts_set err: not oper\n");
                return;
        }
        DBF_EVENT(4, "ts. dev:  %x\n", device->first_minor);
        DBF_EVENT(4, "old ts:\t\n");
        if (device->tape_state < TS_SIZE && device->tape_state >=0 )
                str = tape_state_verbose[device->tape_state];
        else
                str = "UNKNOWN TS";
        DBF_EVENT(4, "%s\n", str);
        DBF_EVENT(4, "new ts:\t\n");
        if (newstate < TS_SIZE && newstate >= 0)
                str = tape_state_verbose[newstate];
        else
                str = "UNKNOWN TS";
        DBF_EVENT(4, "%s\n", str);
        device->tape_state = newstate;
        wake_up(&device->state_change_wq);
}

struct tape_med_state_work_data {
        struct tape_device *device;
        enum tape_medium_state state;
        struct work_struct  work;
};

static void
tape_med_state_work_handler(struct work_struct *work)
{
        static char env_state_loaded[] = "MEDIUM_STATE=LOADED";
        static char env_state_unloaded[] = "MEDIUM_STATE=UNLOADED";
        struct tape_med_state_work_data *p =
                container_of(work, struct tape_med_state_work_data, work);
        struct tape_device *device = p->device;
        char *envp[] = { NULL, NULL };

        switch (p->state) {
        case MS_UNLOADED:
                pr_info("%s: The tape cartridge has been successfully "
                        "unloaded\n", dev_name(&device->cdev->dev));
                envp[0] = env_state_unloaded;
                kobject_uevent_env(&device->cdev->dev.kobj, KOBJ_CHANGE, envp);
                break;
        case MS_LOADED:
                pr_info("%s: A tape cartridge has been mounted\n",
                        dev_name(&device->cdev->dev));
                envp[0] = env_state_loaded;
                kobject_uevent_env(&device->cdev->dev.kobj, KOBJ_CHANGE, envp);
                break;
        default:
                break;
        }
        tape_put_device(device);
        kfree(p);
}

static void
tape_med_state_work(struct tape_device *device, enum tape_medium_state state)
{
        struct tape_med_state_work_data *p;

        p = kzalloc(sizeof(*p), GFP_ATOMIC);
        if (p) {
                INIT_WORK(&p->work, tape_med_state_work_handler);
                p->device = tape_get_device(device);
                p->state = state;
                schedule_work(&p->work);
        }
}

void
tape_med_state_set(struct tape_device *device, enum tape_medium_state newstate)
{
        enum tape_medium_state oldstate;

        oldstate = device->medium_state;
        if (oldstate == newstate)
                return;
        device->medium_state = newstate;
        switch(newstate){
        case MS_UNLOADED:
                device->tape_generic_status |= GMT_DR_OPEN(~0);
                if (oldstate == MS_LOADED)
                        tape_med_state_work(device, MS_UNLOADED);
                break;
        case MS_LOADED:
                device->tape_generic_status &= ~GMT_DR_OPEN(~0);
                if (oldstate == MS_UNLOADED)
                        tape_med_state_work(device, MS_LOADED);
                break;
        default:
                break;
        }
        wake_up(&device->state_change_wq);
}

/*
 * Stop running ccw. Has to be called with the device lock held.
 */
static int
__tape_cancel_io(struct tape_device *device, struct tape_request *request)
{
        int retries;
        int rc;

        /* Check if interrupt has already been processed */
        if (request->callback == NULL)
                return 0;

        rc = 0;
        for (retries = 0; retries < 5; retries++) {
                rc = ccw_device_clear(device->cdev, (long) request);

                switch (rc) {
                        case 0:
                                request->status = TAPE_REQUEST_DONE;
                                return 0;
                        case -EBUSY:
                                request->status = TAPE_REQUEST_CANCEL;
                                schedule_delayed_work(&device->tape_dnr, 0);
                                return 0;
                        case -ENODEV:
                                DBF_EXCEPTION(2, "device gone, retry\n");
                                break;
                        case -EIO:
                                DBF_EXCEPTION(2, "I/O error, retry\n");
                                break;
                        default:
                                BUG();
                }
        }

        return rc;
}

/*
 * Add device into the sorted list, giving it the first
 * available minor number.
 */
static int
tape_assign_minor(struct tape_device *device)
{
        struct tape_device *tmp;
        int minor;

        minor = 0;
        write_lock(&tape_device_lock);
        list_for_each_entry(tmp, &tape_device_list, node) {
                if (minor < tmp->first_minor)
                        break;
                minor += TAPE_MINORS_PER_DEV;
        }
        if (minor >= 256) {
                write_unlock(&tape_device_lock);
                return -ENODEV;
        }
        device->first_minor = minor;
        list_add_tail(&device->node, &tmp->node);
        write_unlock(&tape_device_lock);
        return 0;
}

/* remove device from the list */
static void
tape_remove_minor(struct tape_device *device)
{
        write_lock(&tape_device_lock);
        list_del_init(&device->node);
        device->first_minor = -1;
        write_unlock(&tape_device_lock);
}

/*
 * Set a device online.
 *
 * This function is called by the common I/O layer to move a device from the
 * detected but offline into the online state.
 * If we return an error (RC < 0) the device remains in the offline state. This
 * can happen if the device is assigned somewhere else, for example.
 */
int
tape_generic_online(struct tape_device *device,
                   struct tape_discipline *discipline)
{
        int rc;

        DBF_LH(6, "tape_enable_device(%p, %p)\n", device, discipline);

        if (device->tape_state != TS_INIT) {
                DBF_LH(3, "Tapestate not INIT (%d)\n", device->tape_state);
                return -EINVAL;
        }

        timer_setup(&device->lb_timeout, tape_long_busy_timeout, 0);

        /* Let the discipline have a go at the device. */
        device->discipline = discipline;
        if (!try_module_get(discipline->owner)) {
                return -EINVAL;
        }

        rc = discipline->setup_device(device);
        if (rc)
                goto out;
        rc = tape_assign_minor(device);
        if (rc)
                goto out_discipline;

        rc = tapechar_setup_device(device);
        if (rc)
                goto out_minor;

        tape_state_set(device, TS_UNUSED);

        DBF_LH(3, "(%08x): Drive set online\n", device->cdev_id);

        return 0;

out_minor:
        tape_remove_minor(device);
out_discipline:
        device->discipline->cleanup_device(device);
        device->discipline = NULL;
out:
        module_put(discipline->owner);
        return rc;
}

static void
tape_cleanup_device(struct tape_device *device)
{
        tapechar_cleanup_device(device);
        device->discipline->cleanup_device(device);
        module_put(device->discipline->owner);
        tape_remove_minor(device);
        tape_med_state_set(device, MS_UNKNOWN);
}

/*
 * Suspend device.
 *
 * Called by the common I/O layer if the drive should be suspended on user
 * request. We refuse to suspend if the device is loaded or in use for the
 * following reason:
 * While the Linux guest is suspended, it might be logged off which causes
 * devices to be detached. Tape devices are automatically rewound and unloaded
 * during DETACH processing (unless the tape device was attached with the
 * NOASSIGN or MULTIUSER option). After rewind/unload, there is no way to
 * resume the original state of the tape device, since we would need to
 * manually re-load the cartridge which was active at suspend time.
 */
int tape_generic_pm_suspend(struct ccw_device *cdev)
{
        struct tape_device *device;

        device = dev_get_drvdata(&cdev->dev);
        if (!device) {
                return -ENODEV;
        }

        DBF_LH(3, "(%08x): tape_generic_pm_suspend(%p)\n",
                device->cdev_id, device);

        if (device->medium_state != MS_UNLOADED) {
                pr_err("A cartridge is loaded in tape device %s, "
                       "refusing to suspend\n", dev_name(&cdev->dev));
                return -EBUSY;
        }

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        switch (device->tape_state) {
                case TS_INIT:
                case TS_NOT_OPER:
                case TS_UNUSED:
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        break;
                default:
                        pr_err("Tape device %s is busy, refusing to "
                               "suspend\n", dev_name(&cdev->dev));
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        return -EBUSY;
        }

        DBF_LH(3, "(%08x): Drive suspended.\n", device->cdev_id);
        return 0;
}

/*
 * Set device offline.
 *
 * Called by the common I/O layer if the drive should set offline on user
 * request. We may prevent this by returning an error.
 * Manual offline is only allowed while the drive is not in use.
 */
int
tape_generic_offline(struct ccw_device *cdev)
{
        struct tape_device *device;

        device = dev_get_drvdata(&cdev->dev);
        if (!device) {
                return -ENODEV;
        }

        DBF_LH(3, "(%08x): tape_generic_offline(%p)\n",
                device->cdev_id, device);

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        switch (device->tape_state) {
                case TS_INIT:
                case TS_NOT_OPER:
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        break;
                case TS_UNUSED:
                        tape_state_set(device, TS_INIT);
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        tape_cleanup_device(device);
                        break;
                default:
                        DBF_EVENT(3, "(%08x): Set offline failed "
                                "- drive in use.\n",
                                device->cdev_id);
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        return -EBUSY;
        }

        DBF_LH(3, "(%08x): Drive set offline.\n", device->cdev_id);
        return 0;
}

/*
 * Allocate memory for a new device structure.
 */
static struct tape_device *
tape_alloc_device(void)
{
        struct tape_device *device;

        device = kzalloc(sizeof(struct tape_device), GFP_KERNEL);
        if (device == NULL) {
                DBF_EXCEPTION(2, "ti:no mem\n");
                return ERR_PTR(-ENOMEM);
        }
        device->modeset_byte = kmalloc(1, GFP_KERNEL | GFP_DMA);
        if (device->modeset_byte == NULL) {
                DBF_EXCEPTION(2, "ti:no mem\n");
                kfree(device);
                return ERR_PTR(-ENOMEM);
        }
        mutex_init(&device->mutex);
        INIT_LIST_HEAD(&device->req_queue);
        INIT_LIST_HEAD(&device->node);
        init_waitqueue_head(&device->state_change_wq);
        init_waitqueue_head(&device->wait_queue);
        device->tape_state = TS_INIT;
        device->medium_state = MS_UNKNOWN;
        *device->modeset_byte = 0;
        device->first_minor = -1;
        atomic_set(&device->ref_count, 1);
        INIT_DELAYED_WORK(&device->tape_dnr, tape_delayed_next_request);

        return device;
}

/*
 * Get a reference to an existing device structure. This will automatically
 * increment the reference count.
 */
struct tape_device *
tape_get_device(struct tape_device *device)
{
        int count;

        count = atomic_inc_return(&device->ref_count);
        DBF_EVENT(4, "tape_get_device(%p) = %i\n", device, count);
        return device;
}

/*
 * Decrease the reference counter of a devices structure. If the
 * reference counter reaches zero free the device structure.
 * The function returns a NULL pointer to be used by the caller
 * for clearing reference pointers.
 */
void
tape_put_device(struct tape_device *device)
{
        int count;

        count = atomic_dec_return(&device->ref_count);
        DBF_EVENT(4, "tape_put_device(%p) -> %i\n", device, count);
        BUG_ON(count < 0);
        if (count == 0) {
                kfree(device->modeset_byte);
                kfree(device);
        }
}

/*
 * Find tape device by a device index.
 */
struct tape_device *
tape_find_device(int devindex)
{
        struct tape_device *device, *tmp;

        device = ERR_PTR(-ENODEV);
        read_lock(&tape_device_lock);
        list_for_each_entry(tmp, &tape_device_list, node) {
                if (tmp->first_minor / TAPE_MINORS_PER_DEV == devindex) {
                        device = tape_get_device(tmp);
                        break;
                }
        }
        read_unlock(&tape_device_lock);
        return device;
}

/*
 * Driverfs tape probe function.
 */
int
tape_generic_probe(struct ccw_device *cdev)
{
        struct tape_device *device;
        int ret;
        struct ccw_dev_id dev_id;

        device = tape_alloc_device();
        if (IS_ERR(device))
                return -ENODEV;
        ccw_device_set_options(cdev, CCWDEV_DO_PATHGROUP |
                                     CCWDEV_DO_MULTIPATH);
        ret = sysfs_create_group(&cdev->dev.kobj, &tape_attr_group);
        if (ret) {
                tape_put_device(device);
                return ret;
        }
        dev_set_drvdata(&cdev->dev, device);
        cdev->handler = __tape_do_irq;
        device->cdev = cdev;
        ccw_device_get_id(cdev, &dev_id);
        device->cdev_id = devid_to_int(&dev_id);
        return ret;
}

static void
__tape_discard_requests(struct tape_device *device)
{
        struct tape_request *   request;
        struct list_head *      l, *n;

        list_for_each_safe(l, n, &device->req_queue) {
                request = list_entry(l, struct tape_request, list);
                if (request->status == TAPE_REQUEST_IN_IO)
                        request->status = TAPE_REQUEST_DONE;
                list_del(&request->list);

                /* Decrease ref_count for removed request. */
                request->device = NULL;
                tape_put_device(device);
                request->rc = -EIO;
                if (request->callback != NULL)
                        request->callback(request, request->callback_data);
        }
}

/*
 * Driverfs tape remove function.
 *
 * This function is called whenever the common I/O layer detects the device
 * gone. This can happen at any time and we cannot refuse.
 */
void
tape_generic_remove(struct ccw_device *cdev)
{
        struct tape_device *    device;

        device = dev_get_drvdata(&cdev->dev);
        if (!device) {
                return;
        }
        DBF_LH(3, "(%08x): tape_generic_remove(%p)\n", device->cdev_id, cdev);

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        switch (device->tape_state) {
                case TS_INIT:
                        tape_state_set(device, TS_NOT_OPER);
                case TS_NOT_OPER:
                        /*
                         * Nothing to do.
                         */
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        break;
                case TS_UNUSED:
                        /*
                         * Need only to release the device.
                         */
                        tape_state_set(device, TS_NOT_OPER);
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        tape_cleanup_device(device);
                        break;
                default:
                        /*
                         * There may be requests on the queue. We will not get
                         * an interrupt for a request that was running. So we
                         * just post them all as I/O errors.
                         */
                        DBF_EVENT(3, "(%08x): Drive in use vanished!\n",
                                device->cdev_id);
                        pr_warn("%s: A tape unit was detached while in use\n",
                                dev_name(&device->cdev->dev));
                        tape_state_set(device, TS_NOT_OPER);
                        __tape_discard_requests(device);
                        spin_unlock_irq(get_ccwdev_lock(device->cdev));
                        tape_cleanup_device(device);
        }

        device = dev_get_drvdata(&cdev->dev);
        if (device) {
                sysfs_remove_group(&cdev->dev.kobj, &tape_attr_group);
                dev_set_drvdata(&cdev->dev, NULL);
                tape_put_device(device);
        }
}

/*
 * Allocate a new tape ccw request
 */
struct tape_request *
tape_alloc_request(int cplength, int datasize)
{
        struct tape_request *request;

        BUG_ON(datasize > PAGE_SIZE || (cplength*sizeof(struct ccw1)) > PAGE_SIZE);

        DBF_LH(6, "tape_alloc_request(%d, %d)\n", cplength, datasize);

        request = kzalloc(sizeof(struct tape_request), GFP_KERNEL);
        if (request == NULL) {
                DBF_EXCEPTION(1, "cqra nomem\n");
                return ERR_PTR(-ENOMEM);
        }
        /* allocate channel program */
        if (cplength > 0) {
                request->cpaddr = kcalloc(cplength, sizeof(struct ccw1),
                                          GFP_ATOMIC | GFP_DMA);
                if (request->cpaddr == NULL) {
                        DBF_EXCEPTION(1, "cqra nomem\n");
                        kfree(request);
                        return ERR_PTR(-ENOMEM);
                }
        }
        /* alloc small kernel buffer */
        if (datasize > 0) {
                request->cpdata = kzalloc(datasize, GFP_KERNEL | GFP_DMA);
                if (request->cpdata == NULL) {
                        DBF_EXCEPTION(1, "cqra nomem\n");
                        kfree(request->cpaddr);
                        kfree(request);
                        return ERR_PTR(-ENOMEM);
                }
        }
        DBF_LH(6, "New request %p(%p/%p)\n", request, request->cpaddr,
                request->cpdata);

        return request;
}

/*
 * Free tape ccw request
 */
void
tape_free_request (struct tape_request * request)
{
        DBF_LH(6, "Free request %p\n", request);

        if (request->device)
                tape_put_device(request->device);
        kfree(request->cpdata);
        kfree(request->cpaddr);
        kfree(request);
}

static int
__tape_start_io(struct tape_device *device, struct tape_request *request)
{
        int rc;

        rc = ccw_device_start(
                device->cdev,
                request->cpaddr,
                (unsigned long) request,
                0x00,
                request->options
        );
        if (rc == 0) {
                request->status = TAPE_REQUEST_IN_IO;
        } else if (rc == -EBUSY) {
                /* The common I/O subsystem is currently busy. Retry later. */
                request->status = TAPE_REQUEST_QUEUED;
                schedule_delayed_work(&device->tape_dnr, 0);
                rc = 0;
        } else {
                /* Start failed. Remove request and indicate failure. */
                DBF_EVENT(1, "tape: start request failed with RC = %i\n", rc);
        }
        return rc;
}

static void
__tape_start_next_request(struct tape_device *device)
{
        struct list_head *l, *n;
        struct tape_request *request;
        int rc;

        DBF_LH(6, "__tape_start_next_request(%p)\n", device);
        /*
         * Try to start each request on request queue until one is
         * started successful.
         */
        list_for_each_safe(l, n, &device->req_queue) {
                request = list_entry(l, struct tape_request, list);

                /*
                 * Avoid race condition if bottom-half was triggered more than
                 * once.
                 */
                if (request->status == TAPE_REQUEST_IN_IO)
                        return;
                /*
                 * Request has already been stopped. We have to wait until
                 * the request is removed from the queue in the interrupt
                 * handling.
                 */
                if (request->status == TAPE_REQUEST_DONE)
                        return;

                /*
                 * We wanted to cancel the request but the common I/O layer
                 * was busy at that time. This can only happen if this
                 * function is called by delayed_next_request.
                 * Otherwise we start the next request on the queue.
                 */
                if (request->status == TAPE_REQUEST_CANCEL) {
                        rc = __tape_cancel_io(device, request);
                } else {
                        rc = __tape_start_io(device, request);
                }
                if (rc == 0)
                        return;

                /* Set ending status. */
                request->rc = rc;
                request->status = TAPE_REQUEST_DONE;

                /* Remove from request queue. */
                list_del(&request->list);

                /* Do callback. */
                if (request->callback != NULL)
                        request->callback(request, request->callback_data);
        }
}

static void
tape_delayed_next_request(struct work_struct *work)
{
        struct tape_device *device =
                container_of(work, struct tape_device, tape_dnr.work);

        DBF_LH(6, "tape_delayed_next_request(%p)\n", device);
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        __tape_start_next_request(device);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
}

static void tape_long_busy_timeout(struct timer_list *t)
{
        struct tape_device *device = from_timer(device, t, lb_timeout);
        struct tape_request *request;

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        request = list_entry(device->req_queue.next, struct tape_request, list);
        BUG_ON(request->status != TAPE_REQUEST_LONG_BUSY);
        DBF_LH(6, "%08x: Long busy timeout.\n", device->cdev_id);
        __tape_start_next_request(device);
        tape_put_device(device);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
}

static void
__tape_end_request(
        struct tape_device *    device,
        struct tape_request *   request,
        int                     rc)
{
        DBF_LH(6, "__tape_end_request(%p, %p, %i)\n", device, request, rc);
        if (request) {
                request->rc = rc;
                request->status = TAPE_REQUEST_DONE;

                /* Remove from request queue. */
                list_del(&request->list);

                /* Do callback. */
                if (request->callback != NULL)
                        request->callback(request, request->callback_data);
        }

        /* Start next request. */
        if (!list_empty(&device->req_queue))
                __tape_start_next_request(device);
}

/*
 * Write sense data to dbf
 */
void
tape_dump_sense_dbf(struct tape_device *device, struct tape_request *request,
                    struct irb *irb)
{
        unsigned int *sptr;
        const char* op;

        if (request != NULL)
                op = tape_op_verbose[request->op];
        else
                op = "---";
        DBF_EVENT(3, "DSTAT : %02x   CSTAT: %02x\n",
                  irb->scsw.cmd.dstat, irb->scsw.cmd.cstat);
        DBF_EVENT(3, "DEVICE: %08x OP\t: %s\n", device->cdev_id, op);
        sptr = (unsigned int *) irb->ecw;
        DBF_EVENT(3, "%08x %08x\n", sptr[0], sptr[1]);
        DBF_EVENT(3, "%08x %08x\n", sptr[2], sptr[3]);
        DBF_EVENT(3, "%08x %08x\n", sptr[4], sptr[5]);
        DBF_EVENT(3, "%08x %08x\n", sptr[6], sptr[7]);
}

/*
 * I/O helper function. Adds the request to the request queue
 * and starts it if the tape is idle. Has to be called with
 * the device lock held.
 */
static int
__tape_start_request(struct tape_device *device, struct tape_request *request)
{
        int rc;

        switch (request->op) {
                case TO_MSEN:
                case TO_ASSIGN:
                case TO_UNASSIGN:
                case TO_READ_ATTMSG:
                case TO_RDC:
                        if (device->tape_state == TS_INIT)
                                break;
                        if (device->tape_state == TS_UNUSED)
                                break;
                default:
                        if (device->tape_state == TS_BLKUSE)
                                break;
                        if (device->tape_state != TS_IN_USE)
                                return -ENODEV;
        }

        /* Increase use count of device for the added request. */
        request->device = tape_get_device(device);

        if (list_empty(&device->req_queue)) {
                /* No other requests are on the queue. Start this one. */
                rc = __tape_start_io(device, request);
                if (rc)
                        return rc;

                DBF_LH(5, "Request %p added for execution.\n", request);
                list_add(&request->list, &device->req_queue);
        } else {
                DBF_LH(5, "Request %p add to queue.\n", request);
                request->status = TAPE_REQUEST_QUEUED;
                list_add_tail(&request->list, &device->req_queue);
        }
        return 0;
}

/*
 * Add the request to the request queue, try to start it if the
 * tape is idle. Return without waiting for end of i/o.
 */
int
tape_do_io_async(struct tape_device *device, struct tape_request *request)
{
        int rc;

        DBF_LH(6, "tape_do_io_async(%p, %p)\n", device, request);

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        /* Add request to request queue and try to start it. */
        rc = __tape_start_request(device, request);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        return rc;
}

/*
 * tape_do_io/__tape_wake_up
 * Add the request to the request queue, try to start it if the
 * tape is idle and wait uninterruptible for its completion.
 */
static void
__tape_wake_up(struct tape_request *request, void *data)
{
        request->callback = NULL;
        wake_up((wait_queue_head_t *) data);
}

int
tape_do_io(struct tape_device *device, struct tape_request *request)
{
        int rc;

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        /* Setup callback */
        request->callback = __tape_wake_up;
        request->callback_data = &device->wait_queue;
        /* Add request to request queue and try to start it. */
        rc = __tape_start_request(device, request);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        if (rc)
                return rc;
        /* Request added to the queue. Wait for its completion. */
        wait_event(device->wait_queue, (request->callback == NULL));
        /* Get rc from request */
        return request->rc;
}

/*
 * tape_do_io_interruptible/__tape_wake_up_interruptible
 * Add the request to the request queue, try to start it if the
 * tape is idle and wait uninterruptible for its completion.
 */
static void
__tape_wake_up_interruptible(struct tape_request *request, void *data)
{
        request->callback = NULL;
        wake_up_interruptible((wait_queue_head_t *) data);
}

int
tape_do_io_interruptible(struct tape_device *device,
                         struct tape_request *request)
{
        int rc;

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        /* Setup callback */
        request->callback = __tape_wake_up_interruptible;
        request->callback_data = &device->wait_queue;
        rc = __tape_start_request(device, request);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        if (rc)
                return rc;
        /* Request added to the queue. Wait for its completion. */
        rc = wait_event_interruptible(device->wait_queue,
                                      (request->callback == NULL));
        if (rc != -ERESTARTSYS)
                /* Request finished normally. */
                return request->rc;

        /* Interrupted by a signal. We have to stop the current request. */
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        rc = __tape_cancel_io(device, request);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        if (rc == 0) {
                /* Wait for the interrupt that acknowledges the halt. */
                do {
                        rc = wait_event_interruptible(
                                device->wait_queue,
                                (request->callback == NULL)
                        );
                } while (rc == -ERESTARTSYS);

                DBF_EVENT(3, "IO stopped on %08x\n", device->cdev_id);
                rc = -ERESTARTSYS;
        }
        return rc;
}

/*
 * Stop running ccw.
 */
int
tape_cancel_io(struct tape_device *device, struct tape_request *request)
{
        int rc;

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        rc = __tape_cancel_io(device, request);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        return rc;
}

/*
 * Tape interrupt routine, called from the ccw_device layer
 */
static void
__tape_do_irq (struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
{
        struct tape_device *device;
        struct tape_request *request;
        int rc;

        device = dev_get_drvdata(&cdev->dev);
        if (device == NULL) {
                return;
        }
        request = (struct tape_request *) intparm;

        DBF_LH(6, "__tape_do_irq(device=%p, request=%p)\n", device, request);

        /* On special conditions irb is an error pointer */
        if (IS_ERR(irb)) {
                /* FIXME: What to do with the request? */
                switch (PTR_ERR(irb)) {
                        case -ETIMEDOUT:
                                DBF_LH(1, "(%08x): Request timed out\n",
                                       device->cdev_id);
                        case -EIO:
                                __tape_end_request(device, request, -EIO);
                                break;
                        default:
                                DBF_LH(1, "(%08x): Unexpected i/o error %li\n",
                                       device->cdev_id, PTR_ERR(irb));
                }
                return;
        }

        /*
         * If the condition code is not zero and the start function bit is
         * still set, this is an deferred error and the last start I/O did
         * not succeed. At this point the condition that caused the deferred
         * error might still apply. So we just schedule the request to be
         * started later.
         */
        if (irb->scsw.cmd.cc != 0 &&
            (irb->scsw.cmd.fctl & SCSW_FCTL_START_FUNC) &&
            (request->status == TAPE_REQUEST_IN_IO)) {
                DBF_EVENT(3,"(%08x): deferred cc=%i, fctl=%i. restarting\n",
                        device->cdev_id, irb->scsw.cmd.cc, irb->scsw.cmd.fctl);
                request->status = TAPE_REQUEST_QUEUED;
                schedule_delayed_work(&device->tape_dnr, HZ);
                return;
        }

        /* May be an unsolicited irq */
        if(request != NULL)
                request->rescnt = irb->scsw.cmd.count;
        else if ((irb->scsw.cmd.dstat == 0x85 || irb->scsw.cmd.dstat == 0x80) &&
                 !list_empty(&device->req_queue)) {
                /* Not Ready to Ready after long busy ? */
                struct tape_request *req;
                req = list_entry(device->req_queue.next,
                                 struct tape_request, list);
                if (req->status == TAPE_REQUEST_LONG_BUSY) {
                        DBF_EVENT(3, "(%08x): del timer\n", device->cdev_id);
                        if (del_timer(&device->lb_timeout)) {
                                tape_put_device(device);
                                __tape_start_next_request(device);
                        }
                        return;
                }
        }
        if (irb->scsw.cmd.dstat != 0x0c) {
                /* Set the 'ONLINE' flag depending on sense byte 1 */
                if(*(((__u8 *) irb->ecw) + 1) & SENSE_DRIVE_ONLINE)
                        device->tape_generic_status |= GMT_ONLINE(~0);
                else
                        device->tape_generic_status &= ~GMT_ONLINE(~0);

                /*
                 * Any request that does not come back with channel end
                 * and device end is unusual. Log the sense data.
                 */
                DBF_EVENT(3,"-- Tape Interrupthandler --\n");
                tape_dump_sense_dbf(device, request, irb);
        } else {
                /* Upon normal completion the device _is_ online */
                device->tape_generic_status |= GMT_ONLINE(~0);
        }
        if (device->tape_state == TS_NOT_OPER) {
                DBF_EVENT(6, "tape:device is not operational\n");
                return;
        }

        /*
         * Request that were canceled still come back with an interrupt.
         * To detect these request the state will be set to TAPE_REQUEST_DONE.
         */
        if(request != NULL && request->status == TAPE_REQUEST_DONE) {
                __tape_end_request(device, request, -EIO);
                return;
        }

        rc = device->discipline->irq(device, request, irb);
        /*
         * rc < 0 : request finished unsuccessfully.
         * rc == TAPE_IO_SUCCESS: request finished successfully.
         * rc == TAPE_IO_PENDING: request is still running. Ignore rc.
         * rc == TAPE_IO_RETRY: request finished but needs another go.
         * rc == TAPE_IO_STOP: request needs to get terminated.
         */
        switch (rc) {
                case TAPE_IO_SUCCESS:
                        /* Upon normal completion the device _is_ online */
                        device->tape_generic_status |= GMT_ONLINE(~0);
                        __tape_end_request(device, request, rc);
                        break;
                case TAPE_IO_PENDING:
                        break;
                case TAPE_IO_LONG_BUSY:
                        device->lb_timeout.expires = jiffies +
                                LONG_BUSY_TIMEOUT * HZ;
                        DBF_EVENT(3, "(%08x): add timer\n", device->cdev_id);
                        add_timer(&device->lb_timeout);
                        request->status = TAPE_REQUEST_LONG_BUSY;
                        break;
                case TAPE_IO_RETRY:
                        rc = __tape_start_io(device, request);
                        if (rc)
                                __tape_end_request(device, request, rc);
                        break;
                case TAPE_IO_STOP:
                        rc = __tape_cancel_io(device, request);
                        if (rc)
                                __tape_end_request(device, request, rc);
                        break;
                default:
                        if (rc > 0) {
                                DBF_EVENT(6, "xunknownrc\n");
                                __tape_end_request(device, request, -EIO);
                        } else {
                                __tape_end_request(device, request, rc);
                        }
                        break;
        }
}

/*
 * Tape device open function used by tape_char frontend.
 */
int
tape_open(struct tape_device *device)
{
        int rc;

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        if (device->tape_state == TS_NOT_OPER) {
                DBF_EVENT(6, "TAPE:nodev\n");
                rc = -ENODEV;
        } else if (device->tape_state == TS_IN_USE) {
                DBF_EVENT(6, "TAPE:dbusy\n");
                rc = -EBUSY;
        } else if (device->tape_state == TS_BLKUSE) {
                DBF_EVENT(6, "TAPE:dbusy\n");
                rc = -EBUSY;
        } else if (device->discipline != NULL &&
                   !try_module_get(device->discipline->owner)) {
                DBF_EVENT(6, "TAPE:nodisc\n");
                rc = -ENODEV;
        } else {
                tape_state_set(device, TS_IN_USE);
                rc = 0;
        }
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        return rc;
}

/*
 * Tape device release function used by tape_char frontend.
 */
int
tape_release(struct tape_device *device)
{
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        if (device->tape_state == TS_IN_USE)
                tape_state_set(device, TS_UNUSED);
        module_put(device->discipline->owner);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        return 0;
}

/*
 * Execute a magnetic tape command a number of times.
 */
int
tape_mtop(struct tape_device *device, int mt_op, int mt_count)
{
        tape_mtop_fn fn;
        int rc;

        DBF_EVENT(6, "TAPE:mtio\n");
        DBF_EVENT(6, "TAPE:ioop: %x\n", mt_op);
        DBF_EVENT(6, "TAPE:arg:  %x\n", mt_count);

        if (mt_op < 0 || mt_op >= TAPE_NR_MTOPS)
                return -EINVAL;
        fn = device->discipline->mtop_array[mt_op];
        if (fn == NULL)
                return -EINVAL;

        /* We assume that the backends can handle count up to 500. */
        if (mt_op == MTBSR  || mt_op == MTFSR  || mt_op == MTFSF  ||
            mt_op == MTBSF  || mt_op == MTFSFM || mt_op == MTBSFM) {
                rc = 0;
                for (; mt_count > 500; mt_count -= 500)
                        if ((rc = fn(device, 500)) != 0)
                                break;
                if (rc == 0)
                        rc = fn(device, mt_count);
        } else
                rc = fn(device, mt_count);
        return rc;

}

/*
 * Tape init function.
 */
static int
tape_init (void)
{
        TAPE_DBF_AREA = debug_register ( "tape", 2, 2, 4*sizeof(long));
        debug_register_view(TAPE_DBF_AREA, &debug_sprintf_view);
#ifdef DBF_LIKE_HELL
        debug_set_level(TAPE_DBF_AREA, 6);
#endif
        DBF_EVENT(3, "tape init\n");
        tape_proc_init();
        tapechar_init ();
        return 0;
}

/*
 * Tape exit function.
 */
static void
tape_exit(void)
{
        DBF_EVENT(6, "tape exit\n");

        /* Get rid of the frontends */
        tapechar_exit();
        tape_proc_cleanup();
        debug_unregister (TAPE_DBF_AREA);
}

MODULE_AUTHOR("(C) 2001 IBM Deutschland Entwicklung GmbH by Carsten Otte and "
              "Michael Holzheu (cotte@de.ibm.com,holzheu@de.ibm.com)");
MODULE_DESCRIPTION("Linux on zSeries channel attached tape device driver");
MODULE_LICENSE("GPL");

module_init(tape_init);
module_exit(tape_exit);

EXPORT_SYMBOL(tape_generic_remove);
EXPORT_SYMBOL(tape_generic_probe);
EXPORT_SYMBOL(tape_generic_online);
EXPORT_SYMBOL(tape_generic_offline);
EXPORT_SYMBOL(tape_generic_pm_suspend);
EXPORT_SYMBOL(tape_put_device);
EXPORT_SYMBOL(tape_get_device);
EXPORT_SYMBOL(tape_state_verbose);
EXPORT_SYMBOL(tape_op_verbose);
EXPORT_SYMBOL(tape_state_set);
EXPORT_SYMBOL(tape_med_state_set);
EXPORT_SYMBOL(tape_alloc_request);
EXPORT_SYMBOL(tape_free_request);
EXPORT_SYMBOL(tape_dump_sense_dbf);
EXPORT_SYMBOL(tape_do_io);
EXPORT_SYMBOL(tape_do_io_async);
EXPORT_SYMBOL(tape_do_io_interruptible);
EXPORT_SYMBOL(tape_cancel_io);
EXPORT_SYMBOL(tape_mtop);