Merge git://git.kernel.org/pub/scm/linux/kernel/git/bart/ide-2.6

[linux-2.6] / drivers / s390 / block / dasd.c

/*
 * File...........: linux/drivers/s390/block/dasd.c
 * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
 *                  Horst Hummel <Horst.Hummel@de.ibm.com>
 *                  Carsten Otte <Cotte@de.ibm.com>
 *                  Martin Schwidefsky <schwidefsky@de.ibm.com>
 * Bugreports.to..: <Linux390@de.ibm.com>
 * (C) IBM Corporation, IBM Deutschland Entwicklung GmbH, 1999-2001
 *
 */

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

#include <linux/kmod.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/ctype.h>
#include <linux/major.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include <linux/hdreg.h>

#include <asm/ccwdev.h>
#include <asm/ebcdic.h>
#include <asm/idals.h>
#include <asm/todclk.h>
#include <asm/itcw.h>

/* This is ugly... */
#define PRINTK_HEADER "dasd:"

#include "dasd_int.h"
/*
 * SECTION: Constant definitions to be used within this file
 */
#define DASD_CHANQ_MAX_SIZE 4

/*
 * SECTION: exported variables of dasd.c
 */
debug_info_t *dasd_debug_area;
struct dasd_discipline *dasd_diag_discipline_pointer;
void dasd_int_handler(struct ccw_device *, unsigned long, struct irb *);

MODULE_AUTHOR("Holger Smolinski <Holger.Smolinski@de.ibm.com>");
MODULE_DESCRIPTION("Linux on S/390 DASD device driver,"
                   " Copyright 2000 IBM Corporation");
MODULE_SUPPORTED_DEVICE("dasd");
MODULE_LICENSE("GPL");

/*
 * SECTION: prototypes for static functions of dasd.c
 */
static int  dasd_alloc_queue(struct dasd_block *);
static void dasd_setup_queue(struct dasd_block *);
static void dasd_free_queue(struct dasd_block *);
static void dasd_flush_request_queue(struct dasd_block *);
static int dasd_flush_block_queue(struct dasd_block *);
static void dasd_device_tasklet(struct dasd_device *);
static void dasd_block_tasklet(struct dasd_block *);
static void do_kick_device(struct work_struct *);
static void dasd_return_cqr_cb(struct dasd_ccw_req *, void *);
static void dasd_device_timeout(unsigned long);
static void dasd_block_timeout(unsigned long);

/*
 * SECTION: Operations on the device structure.
 */
static wait_queue_head_t dasd_init_waitq;
static wait_queue_head_t dasd_flush_wq;
static wait_queue_head_t generic_waitq;

/*
 * Allocate memory for a new device structure.
 */
struct dasd_device *dasd_alloc_device(void)
{
        struct dasd_device *device;

        device = kzalloc(sizeof(struct dasd_device), GFP_ATOMIC);
        if (!device)
                return ERR_PTR(-ENOMEM);

        /* Get two pages for normal block device operations. */
        device->ccw_mem = (void *) __get_free_pages(GFP_ATOMIC | GFP_DMA, 1);
        if (!device->ccw_mem) {
                kfree(device);
                return ERR_PTR(-ENOMEM);
        }
        /* Get one page for error recovery. */
        device->erp_mem = (void *) get_zeroed_page(GFP_ATOMIC | GFP_DMA);
        if (!device->erp_mem) {
                free_pages((unsigned long) device->ccw_mem, 1);
                kfree(device);
                return ERR_PTR(-ENOMEM);
        }

        dasd_init_chunklist(&device->ccw_chunks, device->ccw_mem, PAGE_SIZE*2);
        dasd_init_chunklist(&device->erp_chunks, device->erp_mem, PAGE_SIZE);
        spin_lock_init(&device->mem_lock);
        atomic_set(&device->tasklet_scheduled, 0);
        tasklet_init(&device->tasklet,
                     (void (*)(unsigned long)) dasd_device_tasklet,
                     (unsigned long) device);
        INIT_LIST_HEAD(&device->ccw_queue);
        init_timer(&device->timer);
        device->timer.function = dasd_device_timeout;
        device->timer.data = (unsigned long) device;
        INIT_WORK(&device->kick_work, do_kick_device);
        device->state = DASD_STATE_NEW;
        device->target = DASD_STATE_NEW;

        return device;
}

/*
 * Free memory of a device structure.
 */
void dasd_free_device(struct dasd_device *device)
{
        kfree(device->private);
        free_page((unsigned long) device->erp_mem);
        free_pages((unsigned long) device->ccw_mem, 1);
        kfree(device);
}

/*
 * Allocate memory for a new device structure.
 */
struct dasd_block *dasd_alloc_block(void)
{
        struct dasd_block *block;

        block = kzalloc(sizeof(*block), GFP_ATOMIC);
        if (!block)
                return ERR_PTR(-ENOMEM);
        /* open_count = 0 means device online but not in use */
        atomic_set(&block->open_count, -1);

        spin_lock_init(&block->request_queue_lock);
        atomic_set(&block->tasklet_scheduled, 0);
        tasklet_init(&block->tasklet,
                     (void (*)(unsigned long)) dasd_block_tasklet,
                     (unsigned long) block);
        INIT_LIST_HEAD(&block->ccw_queue);
        spin_lock_init(&block->queue_lock);
        init_timer(&block->timer);
        block->timer.function = dasd_block_timeout;
        block->timer.data = (unsigned long) block;

        return block;
}

/*
 * Free memory of a device structure.
 */
void dasd_free_block(struct dasd_block *block)
{
        kfree(block);
}

/*
 * Make a new device known to the system.
 */
static int dasd_state_new_to_known(struct dasd_device *device)
{
        int rc;

        /*
         * As long as the device is not in state DASD_STATE_NEW we want to
         * keep the reference count > 0.
         */
        dasd_get_device(device);

        if (device->block) {
                rc = dasd_alloc_queue(device->block);
                if (rc) {
                        dasd_put_device(device);
                        return rc;
                }
        }
        device->state = DASD_STATE_KNOWN;
        return 0;
}

/*
 * Let the system forget about a device.
 */
static int dasd_state_known_to_new(struct dasd_device *device)
{
        /* Disable extended error reporting for this device. */
        dasd_eer_disable(device);
        /* Forget the discipline information. */
        if (device->discipline) {
                if (device->discipline->uncheck_device)
                        device->discipline->uncheck_device(device);
                module_put(device->discipline->owner);
        }
        device->discipline = NULL;
        if (device->base_discipline)
                module_put(device->base_discipline->owner);
        device->base_discipline = NULL;
        device->state = DASD_STATE_NEW;

        if (device->block)
                dasd_free_queue(device->block);

        /* Give up reference we took in dasd_state_new_to_known. */
        dasd_put_device(device);
        return 0;
}

/*
 * Request the irq line for the device.
 */
static int dasd_state_known_to_basic(struct dasd_device *device)
{
        int rc;

        /* Allocate and register gendisk structure. */
        if (device->block) {
                rc = dasd_gendisk_alloc(device->block);
                if (rc)
                        return rc;
        }
        /* register 'device' debug area, used for all DBF_DEV_XXX calls */
        device->debug_area = debug_register(dev_name(&device->cdev->dev), 4, 1,
                                            8 * sizeof(long));
        debug_register_view(device->debug_area, &debug_sprintf_view);
        debug_set_level(device->debug_area, DBF_WARNING);
        DBF_DEV_EVENT(DBF_EMERG, device, "%s", "debug area created");

        device->state = DASD_STATE_BASIC;
        return 0;
}

/*
 * Release the irq line for the device. Terminate any running i/o.
 */
static int dasd_state_basic_to_known(struct dasd_device *device)
{
        int rc;
        if (device->block) {
                dasd_gendisk_free(device->block);
                dasd_block_clear_timer(device->block);
        }
        rc = dasd_flush_device_queue(device);
        if (rc)
                return rc;
        dasd_device_clear_timer(device);

        DBF_DEV_EVENT(DBF_EMERG, device, "%p debug area deleted", device);
        if (device->debug_area != NULL) {
                debug_unregister(device->debug_area);
                device->debug_area = NULL;
        }
        device->state = DASD_STATE_KNOWN;
        return 0;
}

/*
 * Do the initial analysis. The do_analysis function may return
 * -EAGAIN in which case the device keeps the state DASD_STATE_BASIC
 * until the discipline decides to continue the startup sequence
 * by calling the function dasd_change_state. The eckd disciplines
 * uses this to start a ccw that detects the format. The completion
 * interrupt for this detection ccw uses the kernel event daemon to
 * trigger the call to dasd_change_state. All this is done in the
 * discipline code, see dasd_eckd.c.
 * After the analysis ccw is done (do_analysis returned 0) the block
 * device is setup.
 * In case the analysis returns an error, the device setup is stopped
 * (a fake disk was already added to allow formatting).
 */
static int dasd_state_basic_to_ready(struct dasd_device *device)
{
        int rc;
        struct dasd_block *block;

        rc = 0;
        block = device->block;
        /* make disk known with correct capacity */
        if (block) {
                if (block->base->discipline->do_analysis != NULL)
                        rc = block->base->discipline->do_analysis(block);
                if (rc) {
                        if (rc != -EAGAIN)
                                device->state = DASD_STATE_UNFMT;
                        return rc;
                }
                dasd_setup_queue(block);
                set_capacity(block->gdp,
                             block->blocks << block->s2b_shift);
                device->state = DASD_STATE_READY;
                rc = dasd_scan_partitions(block);
                if (rc)
                        device->state = DASD_STATE_BASIC;
        } else {
                device->state = DASD_STATE_READY;
        }
        return rc;
}

/*
 * Remove device from block device layer. Destroy dirty buffers.
 * Forget format information. Check if the target level is basic
 * and if it is create fake disk for formatting.
 */
static int dasd_state_ready_to_basic(struct dasd_device *device)
{
        int rc;

        device->state = DASD_STATE_BASIC;
        if (device->block) {
                struct dasd_block *block = device->block;
                rc = dasd_flush_block_queue(block);
                if (rc) {
                        device->state = DASD_STATE_READY;
                        return rc;
                }
                dasd_destroy_partitions(block);
                dasd_flush_request_queue(block);
                block->blocks = 0;
                block->bp_block = 0;
                block->s2b_shift = 0;
        }
        return 0;
}

/*
 * Back to basic.
 */
static int dasd_state_unfmt_to_basic(struct dasd_device *device)
{
        device->state = DASD_STATE_BASIC;
        return 0;
}

/*
 * Make the device online and schedule the bottom half to start
 * the requeueing of requests from the linux request queue to the
 * ccw queue.
 */
static int
dasd_state_ready_to_online(struct dasd_device * device)
{
        int rc;
        struct gendisk *disk;
        struct disk_part_iter piter;
        struct hd_struct *part;

        if (device->discipline->ready_to_online) {
                rc = device->discipline->ready_to_online(device);
                if (rc)
                        return rc;
        }
        device->state = DASD_STATE_ONLINE;
        if (device->block) {
                dasd_schedule_block_bh(device->block);
                disk = device->block->bdev->bd_disk;
                disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0);
                while ((part = disk_part_iter_next(&piter)))
                        kobject_uevent(&part_to_dev(part)->kobj, KOBJ_CHANGE);
                disk_part_iter_exit(&piter);
        }
        return 0;
}

/*
 * Stop the requeueing of requests again.
 */
static int dasd_state_online_to_ready(struct dasd_device *device)
{
        int rc;
        struct gendisk *disk;
        struct disk_part_iter piter;
        struct hd_struct *part;

        if (device->discipline->online_to_ready) {
                rc = device->discipline->online_to_ready(device);
                if (rc)
                        return rc;
        }
        device->state = DASD_STATE_READY;
        if (device->block) {
                disk = device->block->bdev->bd_disk;
                disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0);
                while ((part = disk_part_iter_next(&piter)))
                        kobject_uevent(&part_to_dev(part)->kobj, KOBJ_CHANGE);
                disk_part_iter_exit(&piter);
        }
        return 0;
}

/*
 * Device startup state changes.
 */
static int dasd_increase_state(struct dasd_device *device)
{
        int rc;

        rc = 0;
        if (device->state == DASD_STATE_NEW &&
            device->target >= DASD_STATE_KNOWN)
                rc = dasd_state_new_to_known(device);

        if (!rc &&
            device->state == DASD_STATE_KNOWN &&
            device->target >= DASD_STATE_BASIC)
                rc = dasd_state_known_to_basic(device);

        if (!rc &&
            device->state == DASD_STATE_BASIC &&
            device->target >= DASD_STATE_READY)
                rc = dasd_state_basic_to_ready(device);

        if (!rc &&
            device->state == DASD_STATE_UNFMT &&
            device->target > DASD_STATE_UNFMT)
                rc = -EPERM;

        if (!rc &&
            device->state == DASD_STATE_READY &&
            device->target >= DASD_STATE_ONLINE)
                rc = dasd_state_ready_to_online(device);

        return rc;
}

/*
 * Device shutdown state changes.
 */
static int dasd_decrease_state(struct dasd_device *device)
{
        int rc;

        rc = 0;
        if (device->state == DASD_STATE_ONLINE &&
            device->target <= DASD_STATE_READY)
                rc = dasd_state_online_to_ready(device);

        if (!rc &&
            device->state == DASD_STATE_READY &&
            device->target <= DASD_STATE_BASIC)
                rc = dasd_state_ready_to_basic(device);

        if (!rc &&
            device->state == DASD_STATE_UNFMT &&
            device->target <= DASD_STATE_BASIC)
                rc = dasd_state_unfmt_to_basic(device);

        if (!rc &&
            device->state == DASD_STATE_BASIC &&
            device->target <= DASD_STATE_KNOWN)
                rc = dasd_state_basic_to_known(device);

        if (!rc &&
            device->state == DASD_STATE_KNOWN &&
            device->target <= DASD_STATE_NEW)
                rc = dasd_state_known_to_new(device);

        return rc;
}

/*
 * This is the main startup/shutdown routine.
 */
static void dasd_change_state(struct dasd_device *device)
{
        int rc;

        if (device->state == device->target)
                /* Already where we want to go today... */
                return;
        if (device->state < device->target)
                rc = dasd_increase_state(device);
        else
                rc = dasd_decrease_state(device);
        if (rc && rc != -EAGAIN)
                device->target = device->state;

        if (device->state == device->target)
                wake_up(&dasd_init_waitq);

        /* let user-space know that the device status changed */
        kobject_uevent(&device->cdev->dev.kobj, KOBJ_CHANGE);
}

/*
 * Kick starter for devices that did not complete the startup/shutdown
 * procedure or were sleeping because of a pending state.
 * dasd_kick_device will schedule a call do do_kick_device to the kernel
 * event daemon.
 */
static void do_kick_device(struct work_struct *work)
{
        struct dasd_device *device = container_of(work, struct dasd_device, kick_work);
        dasd_change_state(device);
        dasd_schedule_device_bh(device);
        dasd_put_device(device);
}

void dasd_kick_device(struct dasd_device *device)
{
        dasd_get_device(device);
        /* queue call to dasd_kick_device to the kernel event daemon. */
        schedule_work(&device->kick_work);
}

/*
 * Set the target state for a device and starts the state change.
 */
void dasd_set_target_state(struct dasd_device *device, int target)
{
        /* If we are in probeonly mode stop at DASD_STATE_READY. */
        if (dasd_probeonly && target > DASD_STATE_READY)
                target = DASD_STATE_READY;
        if (device->target != target) {
                if (device->state == target)
                        wake_up(&dasd_init_waitq);
                device->target = target;
        }
        if (device->state != device->target)
                dasd_change_state(device);
}

/*
 * Enable devices with device numbers in [from..to].
 */
static inline int _wait_for_device(struct dasd_device *device)
{
        return (device->state == device->target);
}

void dasd_enable_device(struct dasd_device *device)
{
        dasd_set_target_state(device, DASD_STATE_ONLINE);
        if (device->state <= DASD_STATE_KNOWN)
                /* No discipline for device found. */
                dasd_set_target_state(device, DASD_STATE_NEW);
        /* Now wait for the devices to come up. */
        wait_event(dasd_init_waitq, _wait_for_device(device));
}

/*
 * SECTION: device operation (interrupt handler, start i/o, term i/o ...)
 */
#ifdef CONFIG_DASD_PROFILE

struct dasd_profile_info_t dasd_global_profile;
unsigned int dasd_profile_level = DASD_PROFILE_OFF;

/*
 * Increments counter in global and local profiling structures.
 */
#define dasd_profile_counter(value, counter, block) \
{ \
        int index; \
        for (index = 0; index < 31 && value >> (2+index); index++); \
        dasd_global_profile.counter[index]++; \
        block->profile.counter[index]++; \
}

/*
 * Add profiling information for cqr before execution.
 */
static void dasd_profile_start(struct dasd_block *block,
                               struct dasd_ccw_req *cqr,
                               struct request *req)
{
        struct list_head *l;
        unsigned int counter;

        if (dasd_profile_level != DASD_PROFILE_ON)
                return;

        /* count the length of the chanq for statistics */
        counter = 0;
        list_for_each(l, &block->ccw_queue)
                if (++counter >= 31)
                        break;
        dasd_global_profile.dasd_io_nr_req[counter]++;
        block->profile.dasd_io_nr_req[counter]++;
}

/*
 * Add profiling information for cqr after execution.
 */
static void dasd_profile_end(struct dasd_block *block,
                             struct dasd_ccw_req *cqr,
                             struct request *req)
{
        long strtime, irqtime, endtime, tottime;        /* in microseconds */
        long tottimeps, sectors;

        if (dasd_profile_level != DASD_PROFILE_ON)
                return;

        sectors = req->nr_sectors;
        if (!cqr->buildclk || !cqr->startclk ||
            !cqr->stopclk || !cqr->endclk ||
            !sectors)
                return;

        strtime = ((cqr->startclk - cqr->buildclk) >> 12);
        irqtime = ((cqr->stopclk - cqr->startclk) >> 12);
        endtime = ((cqr->endclk - cqr->stopclk) >> 12);
        tottime = ((cqr->endclk - cqr->buildclk) >> 12);
        tottimeps = tottime / sectors;

        if (!dasd_global_profile.dasd_io_reqs)
                memset(&dasd_global_profile, 0,
                       sizeof(struct dasd_profile_info_t));
        dasd_global_profile.dasd_io_reqs++;
        dasd_global_profile.dasd_io_sects += sectors;

        if (!block->profile.dasd_io_reqs)
                memset(&block->profile, 0,
                       sizeof(struct dasd_profile_info_t));
        block->profile.dasd_io_reqs++;
        block->profile.dasd_io_sects += sectors;

        dasd_profile_counter(sectors, dasd_io_secs, block);
        dasd_profile_counter(tottime, dasd_io_times, block);
        dasd_profile_counter(tottimeps, dasd_io_timps, block);
        dasd_profile_counter(strtime, dasd_io_time1, block);
        dasd_profile_counter(irqtime, dasd_io_time2, block);
        dasd_profile_counter(irqtime / sectors, dasd_io_time2ps, block);
        dasd_profile_counter(endtime, dasd_io_time3, block);
}
#else
#define dasd_profile_start(block, cqr, req) do {} while (0)
#define dasd_profile_end(block, cqr, req) do {} while (0)
#endif                          /* CONFIG_DASD_PROFILE */

/*
 * Allocate memory for a channel program with 'cplength' channel
 * command words and 'datasize' additional space. There are two
 * variantes: 1) dasd_kmalloc_request uses kmalloc to get the needed
 * memory and 2) dasd_smalloc_request uses the static ccw memory
 * that gets allocated for each device.
 */
struct dasd_ccw_req *dasd_kmalloc_request(char *magic, int cplength,
                                          int datasize,
                                          struct dasd_device *device)
{
        struct dasd_ccw_req *cqr;

        /* Sanity checks */
        BUG_ON( magic == NULL || datasize > PAGE_SIZE ||
             (cplength*sizeof(struct ccw1)) > PAGE_SIZE);

        cqr = kzalloc(sizeof(struct dasd_ccw_req), GFP_ATOMIC);
        if (cqr == NULL)
                return ERR_PTR(-ENOMEM);
        cqr->cpaddr = NULL;
        if (cplength > 0) {
                cqr->cpaddr = kcalloc(cplength, sizeof(struct ccw1),
                                      GFP_ATOMIC | GFP_DMA);
                if (cqr->cpaddr == NULL) {
                        kfree(cqr);
                        return ERR_PTR(-ENOMEM);
                }
        }
        cqr->data = NULL;
        if (datasize > 0) {
                cqr->data = kzalloc(datasize, GFP_ATOMIC | GFP_DMA);
                if (cqr->data == NULL) {
                        kfree(cqr->cpaddr);
                        kfree(cqr);
                        return ERR_PTR(-ENOMEM);
                }
        }
        strncpy((char *) &cqr->magic, magic, 4);
        ASCEBC((char *) &cqr->magic, 4);
        set_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
        dasd_get_device(device);
        return cqr;
}

struct dasd_ccw_req *dasd_smalloc_request(char *magic, int cplength,
                                          int datasize,
                                          struct dasd_device *device)
{
        unsigned long flags;
        struct dasd_ccw_req *cqr;
        char *data;
        int size;

        /* Sanity checks */
        BUG_ON( magic == NULL || datasize > PAGE_SIZE ||
             (cplength*sizeof(struct ccw1)) > PAGE_SIZE);

        size = (sizeof(struct dasd_ccw_req) + 7L) & -8L;
        if (cplength > 0)
                size += cplength * sizeof(struct ccw1);
        if (datasize > 0)
                size += datasize;
        spin_lock_irqsave(&device->mem_lock, flags);
        cqr = (struct dasd_ccw_req *)
                dasd_alloc_chunk(&device->ccw_chunks, size);
        spin_unlock_irqrestore(&device->mem_lock, flags);
        if (cqr == NULL)
                return ERR_PTR(-ENOMEM);
        memset(cqr, 0, sizeof(struct dasd_ccw_req));
        data = (char *) cqr + ((sizeof(struct dasd_ccw_req) + 7L) & -8L);
        cqr->cpaddr = NULL;
        if (cplength > 0) {
                cqr->cpaddr = (struct ccw1 *) data;
                data += cplength*sizeof(struct ccw1);
                memset(cqr->cpaddr, 0, cplength*sizeof(struct ccw1));
        }
        cqr->data = NULL;
        if (datasize > 0) {
                cqr->data = data;
                memset(cqr->data, 0, datasize);
        }
        strncpy((char *) &cqr->magic, magic, 4);
        ASCEBC((char *) &cqr->magic, 4);
        set_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
        dasd_get_device(device);
        return cqr;
}

/*
 * Free memory of a channel program. This function needs to free all the
 * idal lists that might have been created by dasd_set_cda and the
 * struct dasd_ccw_req itself.
 */
void dasd_kfree_request(struct dasd_ccw_req *cqr, struct dasd_device *device)
{
#ifdef CONFIG_64BIT
        struct ccw1 *ccw;

        /* Clear any idals used for the request. */
        ccw = cqr->cpaddr;
        do {
                clear_normalized_cda(ccw);
        } while (ccw++->flags & (CCW_FLAG_CC | CCW_FLAG_DC));
#endif
        kfree(cqr->cpaddr);
        kfree(cqr->data);
        kfree(cqr);
        dasd_put_device(device);
}

void dasd_sfree_request(struct dasd_ccw_req *cqr, struct dasd_device *device)
{
        unsigned long flags;

        spin_lock_irqsave(&device->mem_lock, flags);
        dasd_free_chunk(&device->ccw_chunks, cqr);
        spin_unlock_irqrestore(&device->mem_lock, flags);
        dasd_put_device(device);
}

/*
 * Check discipline magic in cqr.
 */
static inline int dasd_check_cqr(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;

        if (cqr == NULL)
                return -EINVAL;
        device = cqr->startdev;
        if (strncmp((char *) &cqr->magic, device->discipline->ebcname, 4)) {
                DBF_DEV_EVENT(DBF_WARNING, device,
                            " dasd_ccw_req 0x%08x magic doesn't match"
                            " discipline 0x%08x",
                            cqr->magic,
                            *(unsigned int *) device->discipline->name);
                return -EINVAL;
        }
        return 0;
}

/*
 * Terminate the current i/o and set the request to clear_pending.
 * Timer keeps device runnig.
 * ccw_device_clear can fail if the i/o subsystem
 * is in a bad mood.
 */
int dasd_term_IO(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        int retries, rc;
        char errorstring[ERRORLENGTH];

        /* Check the cqr */
        rc = dasd_check_cqr(cqr);
        if (rc)
                return rc;
        retries = 0;
        device = (struct dasd_device *) cqr->startdev;
        while ((retries < 5) && (cqr->status == DASD_CQR_IN_IO)) {
                rc = ccw_device_clear(device->cdev, (long) cqr);
                switch (rc) {
                case 0: /* termination successful */
                        cqr->retries--;
                        cqr->status = DASD_CQR_CLEAR_PENDING;
                        cqr->stopclk = get_clock();
                        cqr->starttime = 0;
                        DBF_DEV_EVENT(DBF_DEBUG, device,
                                      "terminate cqr %p successful",
                                      cqr);
                        break;
                case -ENODEV:
                        DBF_DEV_EVENT(DBF_ERR, device, "%s",
                                      "device gone, retry");
                        break;
                case -EIO:
                        DBF_DEV_EVENT(DBF_ERR, device, "%s",
                                      "I/O error, retry");
                        break;
                case -EINVAL:
                case -EBUSY:
                        DBF_DEV_EVENT(DBF_ERR, device, "%s",
                                      "device busy, retry later");
                        break;
                default:
                        /* internal error 10 - unknown rc*/
                        snprintf(errorstring, ERRORLENGTH, "10 %d", rc);
                        dev_err(&device->cdev->dev, "An error occurred in the "
                                "DASD device driver, reason=%s\n", errorstring);
                        BUG();
                        break;
                }
                retries++;
        }
        dasd_schedule_device_bh(device);
        return rc;
}

/*
 * Start the i/o. This start_IO can fail if the channel is really busy.
 * In that case set up a timer to start the request later.
 */
int dasd_start_IO(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        int rc;
        char errorstring[ERRORLENGTH];

        /* Check the cqr */
        rc = dasd_check_cqr(cqr);
        if (rc)
                return rc;
        device = (struct dasd_device *) cqr->startdev;
        if (cqr->retries < 0) {
                /* internal error 14 - start_IO run out of retries */
                sprintf(errorstring, "14 %p", cqr);
                dev_err(&device->cdev->dev, "An error occurred in the DASD "
                        "device driver, reason=%s\n", errorstring);
                cqr->status = DASD_CQR_ERROR;
                return -EIO;
        }
        cqr->startclk = get_clock();
        cqr->starttime = jiffies;
        cqr->retries--;
        if (cqr->cpmode == 1) {
                rc = ccw_device_tm_start(device->cdev, cqr->cpaddr,
                                         (long) cqr, cqr->lpm);
        } else {
                rc = ccw_device_start(device->cdev, cqr->cpaddr,
                                      (long) cqr, cqr->lpm, 0);
        }
        switch (rc) {
        case 0:
                cqr->status = DASD_CQR_IN_IO;
                DBF_DEV_EVENT(DBF_DEBUG, device,
                              "start_IO: request %p started successful",
                              cqr);
                break;
        case -EBUSY:
                DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
                              "start_IO: device busy, retry later");
                break;
        case -ETIMEDOUT:
                DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
                              "start_IO: request timeout, retry later");
                break;
        case -EACCES:
                /* -EACCES indicates that the request used only a
                 * subset of the available pathes and all these
                 * pathes are gone.
                 * Do a retry with all available pathes.
                 */
                cqr->lpm = LPM_ANYPATH;
                DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
                              "start_IO: selected pathes gone,"
                              " retry on all pathes");
                break;
        case -ENODEV:
                DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
                              "start_IO: -ENODEV device gone, retry");
                break;
        case -EIO:
                DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
                              "start_IO: -EIO device gone, retry");
                break;
        default:
                /* internal error 11 - unknown rc */
                snprintf(errorstring, ERRORLENGTH, "11 %d", rc);
                dev_err(&device->cdev->dev,
                        "An error occurred in the DASD device driver, "
                        "reason=%s\n", errorstring);
                BUG();
                break;
        }
        return rc;
}

/*
 * Timeout function for dasd devices. This is used for different purposes
 *  1) missing interrupt handler for normal operation
 *  2) delayed start of request where start_IO failed with -EBUSY
 *  3) timeout for missing state change interrupts
 * The head of the ccw queue will have status DASD_CQR_IN_IO for 1),
 * DASD_CQR_QUEUED for 2) and 3).
 */
static void dasd_device_timeout(unsigned long ptr)
{
        unsigned long flags;
        struct dasd_device *device;

        device = (struct dasd_device *) ptr;
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        /* re-activate request queue */
        device->stopped &= ~DASD_STOPPED_PENDING;
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
        dasd_schedule_device_bh(device);
}

/*
 * Setup timeout for a device in jiffies.
 */
void dasd_device_set_timer(struct dasd_device *device, int expires)
{
        if (expires == 0)
                del_timer(&device->timer);
        else
                mod_timer(&device->timer, jiffies + expires);
}

/*
 * Clear timeout for a device.
 */
void dasd_device_clear_timer(struct dasd_device *device)
{
        del_timer(&device->timer);
}

static void dasd_handle_killed_request(struct ccw_device *cdev,
                                       unsigned long intparm)
{
        struct dasd_ccw_req *cqr;
        struct dasd_device *device;

        if (!intparm)
                return;
        cqr = (struct dasd_ccw_req *) intparm;
        if (cqr->status != DASD_CQR_IN_IO) {
                DBF_EVENT(DBF_DEBUG,
                        "invalid status in handle_killed_request: "
                        "bus_id %s, status %02x",
                        dev_name(&cdev->dev), cqr->status);
                return;
        }

        device = (struct dasd_device *) cqr->startdev;
        if (device == NULL ||
            device != dasd_device_from_cdev_locked(cdev) ||
            strncmp(device->discipline->ebcname, (char *) &cqr->magic, 4)) {
                DBF_DEV_EVENT(DBF_DEBUG, device, "invalid device in request: "
                              "bus_id %s", dev_name(&cdev->dev));
                return;
        }

        /* Schedule request to be retried. */
        cqr->status = DASD_CQR_QUEUED;

        dasd_device_clear_timer(device);
        dasd_schedule_device_bh(device);
        dasd_put_device(device);
}

void dasd_generic_handle_state_change(struct dasd_device *device)
{
        /* First of all start sense subsystem status request. */
        dasd_eer_snss(device);

        device->stopped &= ~DASD_STOPPED_PENDING;
        dasd_schedule_device_bh(device);
        if (device->block)
                dasd_schedule_block_bh(device->block);
}

/*
 * Interrupt handler for "normal" ssch-io based dasd devices.
 */
void dasd_int_handler(struct ccw_device *cdev, unsigned long intparm,
                      struct irb *irb)
{
        struct dasd_ccw_req *cqr, *next;
        struct dasd_device *device;
        unsigned long long now;
        int expires;

        if (IS_ERR(irb)) {
                switch (PTR_ERR(irb)) {
                case -EIO:
                        break;
                case -ETIMEDOUT:
                        DBF_EVENT(DBF_WARNING, "%s(%s): request timed out\n",
                               __func__, dev_name(&cdev->dev));
                        break;
                default:
                        DBF_EVENT(DBF_WARNING, "%s(%s): unknown error %ld\n",
                               __func__, dev_name(&cdev->dev), PTR_ERR(irb));
                }
                dasd_handle_killed_request(cdev, intparm);
                return;
        }

        now = get_clock();

        /* check for unsolicited interrupts */
        cqr = (struct dasd_ccw_req *) intparm;
        if (!cqr || ((scsw_cc(&irb->scsw) == 1) &&
                     (scsw_fctl(&irb->scsw) & SCSW_FCTL_START_FUNC) &&
                     (scsw_stctl(&irb->scsw) & SCSW_STCTL_STATUS_PEND))) {
                if (cqr && cqr->status == DASD_CQR_IN_IO)
                        cqr->status = DASD_CQR_QUEUED;
                device = dasd_device_from_cdev_locked(cdev);
                if (!IS_ERR(device)) {
                        dasd_device_clear_timer(device);
                        device->discipline->handle_unsolicited_interrupt(device,
                                                                         irb);
                        dasd_put_device(device);
                }
                return;
        }

        device = (struct dasd_device *) cqr->startdev;
        if (!device ||
            strncmp(device->discipline->ebcname, (char *) &cqr->magic, 4)) {
                DBF_DEV_EVENT(DBF_DEBUG, device, "invalid device in request: "
                              "bus_id %s", dev_name(&cdev->dev));
                return;
        }

        /* Check for clear pending */
        if (cqr->status == DASD_CQR_CLEAR_PENDING &&
            scsw_fctl(&irb->scsw) & SCSW_FCTL_CLEAR_FUNC) {
                cqr->status = DASD_CQR_CLEARED;
                dasd_device_clear_timer(device);
                wake_up(&dasd_flush_wq);
                dasd_schedule_device_bh(device);
                return;
        }

        /* check status - the request might have been killed by dyn detach */
        if (cqr->status != DASD_CQR_IN_IO) {
                DBF_DEV_EVENT(DBF_DEBUG, device, "invalid status: bus_id %s, "
                              "status %02x", dev_name(&cdev->dev), cqr->status);
                return;
        }

        next = NULL;
        expires = 0;
        if (scsw_dstat(&irb->scsw) == (DEV_STAT_CHN_END | DEV_STAT_DEV_END) &&
            scsw_cstat(&irb->scsw) == 0) {
                /* request was completed successfully */
                cqr->status = DASD_CQR_SUCCESS;
                cqr->stopclk = now;
                /* Start first request on queue if possible -> fast_io. */
                if (cqr->devlist.next != &device->ccw_queue) {
                        next = list_entry(cqr->devlist.next,
                                          struct dasd_ccw_req, devlist);
                }
        } else {  /* error */
                memcpy(&cqr->irb, irb, sizeof(struct irb));
                /* log sense for every failed I/O to s390 debugfeature */
                dasd_log_sense_dbf(cqr, irb);
                if (device->features & DASD_FEATURE_ERPLOG) {
                        dasd_log_sense(cqr, irb);
                }

                /*
                 * If we don't want complex ERP for this request, then just
                 * reset this and retry it in the fastpath
                 */
                if (!test_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags) &&
                    cqr->retries > 0) {
                        if (cqr->lpm == LPM_ANYPATH)
                                DBF_DEV_EVENT(DBF_DEBUG, device,
                                              "default ERP in fastpath "
                                              "(%i retries left)",
                                              cqr->retries);
                        cqr->lpm    = LPM_ANYPATH;
                        cqr->status = DASD_CQR_QUEUED;
                        next = cqr;
                } else
                        cqr->status = DASD_CQR_ERROR;
        }
        if (next && (next->status == DASD_CQR_QUEUED) &&
            (!device->stopped)) {
                if (device->discipline->start_IO(next) == 0)
                        expires = next->expires;
        }
        if (expires != 0)
                dasd_device_set_timer(device, expires);
        else
                dasd_device_clear_timer(device);
        dasd_schedule_device_bh(device);
}

/*
 * If we have an error on a dasd_block layer request then we cancel
 * and return all further requests from the same dasd_block as well.
 */
static void __dasd_device_recovery(struct dasd_device *device,
                                   struct dasd_ccw_req *ref_cqr)
{
        struct list_head *l, *n;
        struct dasd_ccw_req *cqr;

        /*
         * only requeue request that came from the dasd_block layer
         */
        if (!ref_cqr->block)
                return;

        list_for_each_safe(l, n, &device->ccw_queue) {
                cqr = list_entry(l, struct dasd_ccw_req, devlist);
                if (cqr->status == DASD_CQR_QUEUED &&
                    ref_cqr->block == cqr->block) {
                        cqr->status = DASD_CQR_CLEARED;
                }
        }
};

/*
 * Remove those ccw requests from the queue that need to be returned
 * to the upper layer.
 */
static void __dasd_device_process_ccw_queue(struct dasd_device *device,
                                            struct list_head *final_queue)
{
        struct list_head *l, *n;
        struct dasd_ccw_req *cqr;

        /* Process request with final status. */
        list_for_each_safe(l, n, &device->ccw_queue) {
                cqr = list_entry(l, struct dasd_ccw_req, devlist);

                /* Stop list processing at the first non-final request. */
                if (cqr->status == DASD_CQR_QUEUED ||
                    cqr->status == DASD_CQR_IN_IO ||
                    cqr->status == DASD_CQR_CLEAR_PENDING)
                        break;
                if (cqr->status == DASD_CQR_ERROR) {
                        __dasd_device_recovery(device, cqr);
                }
                /* Rechain finished requests to final queue */
                list_move_tail(&cqr->devlist, final_queue);
        }
}

/*
 * the cqrs from the final queue are returned to the upper layer
 * by setting a dasd_block state and calling the callback function
 */
static void __dasd_device_process_final_queue(struct dasd_device *device,
                                              struct list_head *final_queue)
{
        struct list_head *l, *n;
        struct dasd_ccw_req *cqr;
        struct dasd_block *block;
        void (*callback)(struct dasd_ccw_req *, void *data);
        void *callback_data;
        char errorstring[ERRORLENGTH];

        list_for_each_safe(l, n, final_queue) {
                cqr = list_entry(l, struct dasd_ccw_req, devlist);
                list_del_init(&cqr->devlist);
                block = cqr->block;
                callback = cqr->callback;
                callback_data = cqr->callback_data;
                if (block)
                        spin_lock_bh(&block->queue_lock);
                switch (cqr->status) {
                case DASD_CQR_SUCCESS:
                        cqr->status = DASD_CQR_DONE;
                        break;
                case DASD_CQR_ERROR:
                        cqr->status = DASD_CQR_NEED_ERP;
                        break;
                case DASD_CQR_CLEARED:
                        cqr->status = DASD_CQR_TERMINATED;
                        break;
                default:
                        /* internal error 12 - wrong cqr status*/
                        snprintf(errorstring, ERRORLENGTH, "12 %p %x02", cqr, cqr->status);
                        dev_err(&device->cdev->dev,
                                "An error occurred in the DASD device driver, "
                                "reason=%s\n", errorstring);
                        BUG();
                }
                if (cqr->callback != NULL)
                        (callback)(cqr, callback_data);
                if (block)
                        spin_unlock_bh(&block->queue_lock);
        }
}

/*
 * Take a look at the first request on the ccw queue and check
 * if it reached its expire time. If so, terminate the IO.
 */
static void __dasd_device_check_expire(struct dasd_device *device)
{
        struct dasd_ccw_req *cqr;

        if (list_empty(&device->ccw_queue))
                return;
        cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, devlist);
        if ((cqr->status == DASD_CQR_IN_IO && cqr->expires != 0) &&
            (time_after_eq(jiffies, cqr->expires + cqr->starttime))) {
                if (device->discipline->term_IO(cqr) != 0) {
                        /* Hmpf, try again in 5 sec */
                        dev_err(&device->cdev->dev,
                                "cqr %p timed out (%is) but cannot be "
                                "ended, retrying in 5 s\n",
                                cqr, (cqr->expires/HZ));
                        cqr->expires += 5*HZ;
                        dasd_device_set_timer(device, 5*HZ);
                } else {
                        dev_err(&device->cdev->dev,
                                "cqr %p timed out (%is), %i retries "
                                "remaining\n", cqr, (cqr->expires/HZ),
                                cqr->retries);
                }
        }
}

/*
 * Take a look at the first request on the ccw queue and check
 * if it needs to be started.
 */
static void __dasd_device_start_head(struct dasd_device *device)
{
        struct dasd_ccw_req *cqr;
        int rc;

        if (list_empty(&device->ccw_queue))
                return;
        cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, devlist);
        if (cqr->status != DASD_CQR_QUEUED)
                return;
        /* when device is stopped, return request to previous layer */
        if (device->stopped) {
                cqr->status = DASD_CQR_CLEARED;
                dasd_schedule_device_bh(device);
                return;
        }

        rc = device->discipline->start_IO(cqr);
        if (rc == 0)
                dasd_device_set_timer(device, cqr->expires);
        else if (rc == -EACCES) {
                dasd_schedule_device_bh(device);
        } else
                /* Hmpf, try again in 1/2 sec */
                dasd_device_set_timer(device, 50);
}

/*
 * Go through all request on the dasd_device request queue,
 * terminate them on the cdev if necessary, and return them to the
 * submitting layer via callback.
 * Note:
 * Make sure that all 'submitting layers' still exist when
 * this function is called!. In other words, when 'device' is a base
 * device then all block layer requests must have been removed before
 * via dasd_flush_block_queue.
 */
int dasd_flush_device_queue(struct dasd_device *device)
{
        struct dasd_ccw_req *cqr, *n;
        int rc;
        struct list_head flush_queue;

        INIT_LIST_HEAD(&flush_queue);
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        rc = 0;
        list_for_each_entry_safe(cqr, n, &device->ccw_queue, devlist) {
                /* Check status and move request to flush_queue */
                switch (cqr->status) {
                case DASD_CQR_IN_IO:
                        rc = device->discipline->term_IO(cqr);
                        if (rc) {
                                /* unable to terminate requeust */
                                dev_err(&device->cdev->dev,
                                        "Flushing the DASD request queue "
                                        "failed for request %p\n", cqr);
                                /* stop flush processing */
                                goto finished;
                        }
                        break;
                case DASD_CQR_QUEUED:
                        cqr->stopclk = get_clock();
                        cqr->status = DASD_CQR_CLEARED;
                        break;
                default: /* no need to modify the others */
                        break;
                }
                list_move_tail(&cqr->devlist, &flush_queue);
        }
finished:
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        /*
         * After this point all requests must be in state CLEAR_PENDING,
         * CLEARED, SUCCESS or ERROR. Now wait for CLEAR_PENDING to become
         * one of the others.
         */
        list_for_each_entry_safe(cqr, n, &flush_queue, devlist)
                wait_event(dasd_flush_wq,
                           (cqr->status != DASD_CQR_CLEAR_PENDING));
        /*
         * Now set each request back to TERMINATED, DONE or NEED_ERP
         * and call the callback function of flushed requests
         */
        __dasd_device_process_final_queue(device, &flush_queue);
        return rc;
}

/*
 * Acquire the device lock and process queues for the device.
 */
static void dasd_device_tasklet(struct dasd_device *device)
{
        struct list_head final_queue;

        atomic_set (&device->tasklet_scheduled, 0);
        INIT_LIST_HEAD(&final_queue);
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        /* Check expire time of first request on the ccw queue. */
        __dasd_device_check_expire(device);
        /* find final requests on ccw queue */
        __dasd_device_process_ccw_queue(device, &final_queue);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        /* Now call the callback function of requests with final status */
        __dasd_device_process_final_queue(device, &final_queue);
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        /* Now check if the head of the ccw queue needs to be started. */
        __dasd_device_start_head(device);
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        dasd_put_device(device);
}

/*
 * Schedules a call to dasd_tasklet over the device tasklet.
 */
void dasd_schedule_device_bh(struct dasd_device *device)
{
        /* Protect against rescheduling. */
        if (atomic_cmpxchg (&device->tasklet_scheduled, 0, 1) != 0)
                return;
        dasd_get_device(device);
        tasklet_hi_schedule(&device->tasklet);
}

/*
 * Queue a request to the head of the device ccw_queue.
 * Start the I/O if possible.
 */
void dasd_add_request_head(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        unsigned long flags;

        device = cqr->startdev;
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        cqr->status = DASD_CQR_QUEUED;
        list_add(&cqr->devlist, &device->ccw_queue);
        /* let the bh start the request to keep them in order */
        dasd_schedule_device_bh(device);
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
}

/*
 * Queue a request to the tail of the device ccw_queue.
 * Start the I/O if possible.
 */
void dasd_add_request_tail(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        unsigned long flags;

        device = cqr->startdev;
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        cqr->status = DASD_CQR_QUEUED;
        list_add_tail(&cqr->devlist, &device->ccw_queue);
        /* let the bh start the request to keep them in order */
        dasd_schedule_device_bh(device);
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
}

/*
 * Wakeup helper for the 'sleep_on' functions.
 */
static void dasd_wakeup_cb(struct dasd_ccw_req *cqr, void *data)
{
        wake_up((wait_queue_head_t *) data);
}

static inline int _wait_for_wakeup(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        int rc;

        device = cqr->startdev;
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        rc = ((cqr->status == DASD_CQR_DONE ||
               cqr->status == DASD_CQR_NEED_ERP ||
               cqr->status == DASD_CQR_TERMINATED) &&
              list_empty(&cqr->devlist));
        spin_unlock_irq(get_ccwdev_lock(device->cdev));
        return rc;
}

/*
 * Queue a request to the tail of the device ccw_queue and wait for
 * it's completion.
 */
int dasd_sleep_on(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        int rc;

        device = cqr->startdev;

        cqr->callback = dasd_wakeup_cb;
        cqr->callback_data = (void *) &generic_waitq;
        dasd_add_request_tail(cqr);
        wait_event(generic_waitq, _wait_for_wakeup(cqr));

        /* Request status is either done or failed. */
        rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
        return rc;
}

/*
 * Queue a request to the tail of the device ccw_queue and wait
 * interruptible for it's completion.
 */
int dasd_sleep_on_interruptible(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        int rc;

        device = cqr->startdev;
        cqr->callback = dasd_wakeup_cb;
        cqr->callback_data = (void *) &generic_waitq;
        dasd_add_request_tail(cqr);
        rc = wait_event_interruptible(generic_waitq, _wait_for_wakeup(cqr));
        if (rc == -ERESTARTSYS) {
                dasd_cancel_req(cqr);
                /* wait (non-interruptible) for final status */
                wait_event(generic_waitq, _wait_for_wakeup(cqr));
        }
        rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
        return rc;
}

/*
 * Whoa nelly now it gets really hairy. For some functions (e.g. steal lock
 * for eckd devices) the currently running request has to be terminated
 * and be put back to status queued, before the special request is added
 * to the head of the queue. Then the special request is waited on normally.
 */
static inline int _dasd_term_running_cqr(struct dasd_device *device)
{
        struct dasd_ccw_req *cqr;

        if (list_empty(&device->ccw_queue))
                return 0;
        cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, devlist);
        return device->discipline->term_IO(cqr);
}

int dasd_sleep_on_immediatly(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device;
        int rc;

        device = cqr->startdev;
        spin_lock_irq(get_ccwdev_lock(device->cdev));
        rc = _dasd_term_running_cqr(device);
        if (rc) {
                spin_unlock_irq(get_ccwdev_lock(device->cdev));
                return rc;
        }

        cqr->callback = dasd_wakeup_cb;
        cqr->callback_data = (void *) &generic_waitq;
        cqr->status = DASD_CQR_QUEUED;
        list_add(&cqr->devlist, &device->ccw_queue);

        /* let the bh start the request to keep them in order */
        dasd_schedule_device_bh(device);

        spin_unlock_irq(get_ccwdev_lock(device->cdev));

        wait_event(generic_waitq, _wait_for_wakeup(cqr));

        /* Request status is either done or failed. */
        rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
        return rc;
}

/*
 * Cancels a request that was started with dasd_sleep_on_req.
 * This is useful to timeout requests. The request will be
 * terminated if it is currently in i/o.
 * Returns 1 if the request has been terminated.
 *         0 if there was no need to terminate the request (not started yet)
 *         negative error code if termination failed
 * Cancellation of a request is an asynchronous operation! The calling
 * function has to wait until the request is properly returned via callback.
 */
int dasd_cancel_req(struct dasd_ccw_req *cqr)
{
        struct dasd_device *device = cqr->startdev;
        unsigned long flags;
        int rc;

        rc = 0;
        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
        switch (cqr->status) {
        case DASD_CQR_QUEUED:
                /* request was not started - just set to cleared */
                cqr->status = DASD_CQR_CLEARED;
                break;
        case DASD_CQR_IN_IO:
                /* request in IO - terminate IO and release again */
                rc = device->discipline->term_IO(cqr);
                if (rc) {
                        dev_err(&device->cdev->dev,
                                "Cancelling request %p failed with rc=%d\n",
                                cqr, rc);
                } else {
                        cqr->stopclk = get_clock();
                        rc = 1;
                }
                break;
        default: /* already finished or clear pending - do nothing */
                break;
        }
        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
        dasd_schedule_device_bh(device);
        return rc;
}


/*
 * SECTION: Operations of the dasd_block layer.
 */

/*
 * Timeout function for dasd_block. This is used when the block layer
 * is waiting for something that may not come reliably, (e.g. a state
 * change interrupt)
 */
static void dasd_block_timeout(unsigned long ptr)
{
        unsigned long flags;
        struct dasd_block *block;

        block = (struct dasd_block *) ptr;
        spin_lock_irqsave(get_ccwdev_lock(block->base->cdev), flags);
        /* re-activate request queue */
        block->base->stopped &= ~DASD_STOPPED_PENDING;
        spin_unlock_irqrestore(get_ccwdev_lock(block->base->cdev), flags);
        dasd_schedule_block_bh(block);
}

/*
 * Setup timeout for a dasd_block in jiffies.
 */
void dasd_block_set_timer(struct dasd_block *block, int expires)
{
        if (expires == 0)
                del_timer(&block->timer);
        else
                mod_timer(&block->timer, jiffies + expires);
}

/*
 * Clear timeout for a dasd_block.
 */
void dasd_block_clear_timer(struct dasd_block *block)
{
        del_timer(&block->timer);
}

/*
 * posts the buffer_cache about a finalized request
 */
static inline void dasd_end_request(struct request *req, int error)
{
        if (__blk_end_request(req, error, blk_rq_bytes(req)))
                BUG();
}

/*
 * Process finished error recovery ccw.
 */
static inline void __dasd_block_process_erp(struct dasd_block *block,
                                            struct dasd_ccw_req *cqr)
{
        dasd_erp_fn_t erp_fn;
        struct dasd_device *device = block->base;

        if (cqr->status == DASD_CQR_DONE)
                DBF_DEV_EVENT(DBF_NOTICE, device, "%s", "ERP successful");
        else
                dev_err(&device->cdev->dev, "ERP failed for the DASD\n");
        erp_fn = device->discipline->erp_postaction(cqr);
        erp_fn(cqr);
}

/*
 * Fetch requests from the block device queue.
 */
static void __dasd_process_request_queue(struct dasd_block *block)
{
        struct request_queue *queue;
        struct request *req;
        struct dasd_ccw_req *cqr;
        struct dasd_device *basedev;
        unsigned long flags;
        queue = block->request_queue;
        basedev = block->base;
        /* No queue ? Then there is nothing to do. */
        if (queue == NULL)
                return;

        /*
         * We requeue request from the block device queue to the ccw
         * queue only in two states. In state DASD_STATE_READY the
         * partition detection is done and we need to requeue requests
         * for that. State DASD_STATE_ONLINE is normal block device
         * operation.
         */
        if (basedev->state < DASD_STATE_READY)
                return;
        /* Now we try to fetch requests from the request queue */
        while (!blk_queue_plugged(queue) &&
               elv_next_request(queue)) {

                req = elv_next_request(queue);

                if (basedev->features & DASD_FEATURE_READONLY &&
                    rq_data_dir(req) == WRITE) {
                        DBF_DEV_EVENT(DBF_ERR, basedev,
                                      "Rejecting write request %p",
                                      req);
                        blkdev_dequeue_request(req);
                        dasd_end_request(req, -EIO);
                        continue;
                }
                cqr = basedev->discipline->build_cp(basedev, block, req);
                if (IS_ERR(cqr)) {
                        if (PTR_ERR(cqr) == -EBUSY)
                                break;  /* normal end condition */
                        if (PTR_ERR(cqr) == -ENOMEM)
                                break;  /* terminate request queue loop */
                        if (PTR_ERR(cqr) == -EAGAIN) {
                                /*
                                 * The current request cannot be build right
                                 * now, we have to try later. If this request
                                 * is the head-of-queue we stop the device
                                 * for 1/2 second.
                                 */
                                if (!list_empty(&block->ccw_queue))
                                        break;
                                spin_lock_irqsave(get_ccwdev_lock(basedev->cdev), flags);
                                basedev->stopped |= DASD_STOPPED_PENDING;
                                spin_unlock_irqrestore(get_ccwdev_lock(basedev->cdev), flags);
                                dasd_block_set_timer(block, HZ/2);
                                break;
                        }
                        DBF_DEV_EVENT(DBF_ERR, basedev,
                                      "CCW creation failed (rc=%ld) "
                                      "on request %p",
                                      PTR_ERR(cqr), req);
                        blkdev_dequeue_request(req);
                        dasd_end_request(req, -EIO);
                        continue;
                }
                /*
                 *  Note: callback is set to dasd_return_cqr_cb in
                 * __dasd_block_start_head to cover erp requests as well
                 */
                cqr->callback_data = (void *) req;
                cqr->status = DASD_CQR_FILLED;
                blkdev_dequeue_request(req);
                list_add_tail(&cqr->blocklist, &block->ccw_queue);
                dasd_profile_start(block, cqr, req);
        }
}

static void __dasd_cleanup_cqr(struct dasd_ccw_req *cqr)
{
        struct request *req;
        int status;
        int error = 0;

        req = (struct request *) cqr->callback_data;
        dasd_profile_end(cqr->block, cqr, req);
        status = cqr->block->base->discipline->free_cp(cqr, req);
        if (status <= 0)
                error = status ? status : -EIO;
        dasd_end_request(req, error);
}

/*
 * Process ccw request queue.
 */
static void __dasd_process_block_ccw_queue(struct dasd_block *block,
                                           struct list_head *final_queue)
{
        struct list_head *l, *n;
        struct dasd_ccw_req *cqr;
        dasd_erp_fn_t erp_fn;
        unsigned long flags;
        struct dasd_device *base = block->base;

restart:
        /* Process request with final status. */
        list_for_each_safe(l, n, &block->ccw_queue) {
                cqr = list_entry(l, struct dasd_ccw_req, blocklist);
                if (cqr->status != DASD_CQR_DONE &&
                    cqr->status != DASD_CQR_FAILED &&
                    cqr->status != DASD_CQR_NEED_ERP &&
                    cqr->status != DASD_CQR_TERMINATED)
                        continue;

                if (cqr->status == DASD_CQR_TERMINATED) {
                        base->discipline->handle_terminated_request(cqr);
                        goto restart;
                }

                /*  Process requests that may be recovered */
                if (cqr->status == DASD_CQR_NEED_ERP) {
                        erp_fn = base->discipline->erp_action(cqr);
                        erp_fn(cqr);
                        goto restart;
                }

                /* log sense for fatal error */
                if (cqr->status == DASD_CQR_FAILED) {
                        dasd_log_sense(cqr, &cqr->irb);
                }

                /* First of all call extended error reporting. */
                if (dasd_eer_enabled(base) &&
                    cqr->status == DASD_CQR_FAILED) {
                        dasd_eer_write(base, cqr, DASD_EER_FATALERROR);

                        /* restart request  */
                        cqr->status = DASD_CQR_FILLED;
                        cqr->retries = 255;
                        spin_lock_irqsave(get_ccwdev_lock(base->cdev), flags);
                        base->stopped |= DASD_STOPPED_QUIESCE;
                        spin_unlock_irqrestore(get_ccwdev_lock(base->cdev),
                                               flags);
                        goto restart;
                }

                /* Process finished ERP request. */
                if (cqr->refers) {
                        __dasd_block_process_erp(block, cqr);
                        goto restart;
                }

                /* Rechain finished requests to final queue */
                cqr->endclk = get_clock();
                list_move_tail(&cqr->blocklist, final_queue);
        }
}

static void dasd_return_cqr_cb(struct dasd_ccw_req *cqr, void *data)
{
        dasd_schedule_block_bh(cqr->block);
}

static void __dasd_block_start_head(struct dasd_block *block)
{
        struct dasd_ccw_req *cqr;

        if (list_empty(&block->ccw_queue))
                return;
        /* We allways begin with the first requests on the queue, as some
         * of previously started requests have to be enqueued on a
         * dasd_device again for error recovery.
         */
        list_for_each_entry(cqr, &block->ccw_queue, blocklist) {
                if (cqr->status != DASD_CQR_FILLED)
                        continue;
                /* Non-temporary stop condition will trigger fail fast */
                if (block->base->stopped & ~DASD_STOPPED_PENDING &&
                    test_bit(DASD_CQR_FLAGS_FAILFAST, &cqr->flags) &&
                    (!dasd_eer_enabled(block->base))) {
                        cqr->status = DASD_CQR_FAILED;
                        dasd_schedule_block_bh(block);
                        continue;
                }
                /* Don't try to start requests if device is stopped */
                if (block->base->stopped)
                        return;

                /* just a fail safe check, should not happen */
                if (!cqr->startdev)
                        cqr->startdev = block->base;

                /* make sure that the requests we submit find their way back */
                cqr->callback = dasd_return_cqr_cb;

                dasd_add_request_tail(cqr);
        }
}

/*
 * Central dasd_block layer routine. Takes requests from the generic
 * block layer request queue, creates ccw requests, enqueues them on
 * a dasd_device and processes ccw requests that have been returned.
 */
static void dasd_block_tasklet(struct dasd_block *block)
{
        struct list_head final_queue;
        struct list_head *l, *n;
        struct dasd_ccw_req *cqr;

        atomic_set(&block->tasklet_scheduled, 0);
        INIT_LIST_HEAD(&final_queue);
        spin_lock(&block->queue_lock);
        /* Finish off requests on ccw queue */
        __dasd_process_block_ccw_queue(block, &final_queue);
        spin_unlock(&block->queue_lock);
        /* Now call the callback function of requests with final status */
        spin_lock_irq(&block->request_queue_lock);
        list_for_each_safe(l, n, &final_queue) {
                cqr = list_entry(l, struct dasd_ccw_req, blocklist);
                list_del_init(&cqr->blocklist);
                __dasd_cleanup_cqr(cqr);
        }
        spin_lock(&block->queue_lock);
        /* Get new request from the block device request queue */
        __dasd_process_request_queue(block);
        /* Now check if the head of the ccw queue needs to be started. */
        __dasd_block_start_head(block);
        spin_unlock(&block->queue_lock);
        spin_unlock_irq(&block->request_queue_lock);
        dasd_put_device(block->base);
}

static void _dasd_wake_block_flush_cb(struct dasd_ccw_req *cqr, void *data)
{
        wake_up(&dasd_flush_wq);
}

/*
 * Go through all request on the dasd_block request queue, cancel them
 * on the respective dasd_device, and return them to the generic
 * block layer.
 */
static int dasd_flush_block_queue(struct dasd_block *block)
{
        struct dasd_ccw_req *cqr, *n;
        int rc, i;
        struct list_head flush_queue;

        INIT_LIST_HEAD(&flush_queue);
        spin_lock_bh(&block->queue_lock);
        rc = 0;
restart:
        list_for_each_entry_safe(cqr, n, &block->ccw_queue, blocklist) {
                /* if this request currently owned by a dasd_device cancel it */
                if (cqr->status >= DASD_CQR_QUEUED)
                        rc = dasd_cancel_req(cqr);
                if (rc < 0)
                        break;
                /* Rechain request (including erp chain) so it won't be
                 * touched by the dasd_block_tasklet anymore.
                 * Replace the callback so we notice when the request
                 * is returned from the dasd_device layer.
                 */
                cqr->callback = _dasd_wake_block_flush_cb;
                for (i = 0; cqr != NULL; cqr = cqr->refers, i++)
                        list_move_tail(&cqr->blocklist, &flush_queue);
                if (i > 1)
                        /* moved more than one request - need to restart */
                        goto restart;
        }
        spin_unlock_bh(&block->queue_lock);
        /* Now call the callback function of flushed requests */
restart_cb:
        list_for_each_entry_safe(cqr, n, &flush_queue, blocklist) {
                wait_event(dasd_flush_wq, (cqr->status < DASD_CQR_QUEUED));
                /* Process finished ERP request. */
                if (cqr->refers) {
                        spin_lock_bh(&block->queue_lock);
                        __dasd_block_process_erp(block, cqr);
                        spin_unlock_bh(&block->queue_lock);
                        /* restart list_for_xx loop since dasd_process_erp
                         * might remove multiple elements */
                        goto restart_cb;
                }
                /* call the callback function */
                spin_lock_irq(&block->request_queue_lock);
                cqr->endclk = get_clock();
                list_del_init(&cqr->blocklist);
                __dasd_cleanup_cqr(cqr);
                spin_unlock_irq(&block->request_queue_lock);
        }
        return rc;
}

/*
 * Schedules a call to dasd_tasklet over the device tasklet.
 */
void dasd_schedule_block_bh(struct dasd_block *block)
{
        /* Protect against rescheduling. */
        if (atomic_cmpxchg(&block->tasklet_scheduled, 0, 1) != 0)
                return;
        /* life cycle of block is bound to it's base device */
        dasd_get_device(block->base);
        tasklet_hi_schedule(&block->tasklet);
}


/*
 * SECTION: external block device operations
 * (request queue handling, open, release, etc.)
 */

/*
 * Dasd request queue function. Called from ll_rw_blk.c
 */
static void do_dasd_request(struct request_queue *queue)
{
        struct dasd_block *block;

        block = queue->queuedata;
        spin_lock(&block->queue_lock);
        /* Get new request from the block device request queue */
        __dasd_process_request_queue(block);
        /* Now check if the head of the ccw queue needs to be started. */
        __dasd_block_start_head(block);
        spin_unlock(&block->queue_lock);
}

/*
 * Allocate and initialize request queue and default I/O scheduler.
 */
static int dasd_alloc_queue(struct dasd_block *block)
{
        int rc;

        block->request_queue = blk_init_queue(do_dasd_request,
                                               &block->request_queue_lock);
        if (block->request_queue == NULL)
                return -ENOMEM;

        block->request_queue->queuedata = block;

        elevator_exit(block->request_queue->elevator);
        block->request_queue->elevator = NULL;
        rc = elevator_init(block->request_queue, "deadline");
        if (rc) {
                blk_cleanup_queue(block->request_queue);
                return rc;
        }
        return 0;
}

/*
 * Allocate and initialize request queue.
 */
static void dasd_setup_queue(struct dasd_block *block)
{
        int max;

        blk_queue_hardsect_size(block->request_queue, block->bp_block);
        max = block->base->discipline->max_blocks << block->s2b_shift;
        blk_queue_max_sectors(block->request_queue, max);
        blk_queue_max_phys_segments(block->request_queue, -1L);
        blk_queue_max_hw_segments(block->request_queue, -1L);
        /* with page sized segments we can translate each segement into
         * one idaw/tidaw
         */
        blk_queue_max_segment_size(block->request_queue, PAGE_SIZE);
        blk_queue_segment_boundary(block->request_queue, PAGE_SIZE - 1);
        blk_queue_ordered(block->request_queue, QUEUE_ORDERED_DRAIN, NULL);
}

/*
 * Deactivate and free request queue.
 */
static void dasd_free_queue(struct dasd_block *block)
{
        if (block->request_queue) {
                blk_cleanup_queue(block->request_queue);
                block->request_queue = NULL;
        }
}

/*
 * Flush request on the request queue.
 */
static void dasd_flush_request_queue(struct dasd_block *block)
{
        struct request *req;

        if (!block->request_queue)
                return;

        spin_lock_irq(&block->request_queue_lock);
        while ((req = elv_next_request(block->request_queue))) {
                blkdev_dequeue_request(req);
                dasd_end_request(req, -EIO);
        }
        spin_unlock_irq(&block->request_queue_lock);
}

static int dasd_open(struct block_device *bdev, fmode_t mode)
{
        struct dasd_block *block = bdev->bd_disk->private_data;
        struct dasd_device *base = block->base;
        int rc;

        atomic_inc(&block->open_count);
        if (test_bit(DASD_FLAG_OFFLINE, &base->flags)) {
                rc = -ENODEV;
                goto unlock;
        }

        if (!try_module_get(base->discipline->owner)) {
                rc = -EINVAL;
                goto unlock;
        }

        if (dasd_probeonly) {
                dev_info(&base->cdev->dev,
                         "Accessing the DASD failed because it is in "
                         "probeonly mode\n");
                rc = -EPERM;
                goto out;
        }

        if (base->state <= DASD_STATE_BASIC) {
                DBF_DEV_EVENT(DBF_ERR, base, " %s",
                              " Cannot open unrecognized device");
                rc = -ENODEV;
                goto out;
        }

        return 0;

out:
        module_put(base->discipline->owner);
unlock:
        atomic_dec(&block->open_count);
        return rc;
}

static int dasd_release(struct gendisk *disk, fmode_t mode)
{
        struct dasd_block *block = disk->private_data;

        atomic_dec(&block->open_count);
        module_put(block->base->discipline->owner);
        return 0;
}

/*
 * Return disk geometry.
 */
static int dasd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
        struct dasd_block *block;
        struct dasd_device *base;

        block = bdev->bd_disk->private_data;
        base = block->base;
        if (!block)
                return -ENODEV;

        if (!base->discipline ||
            !base->discipline->fill_geometry)
                return -EINVAL;

        base->discipline->fill_geometry(block, geo);
        geo->start = get_start_sect(bdev) >> block->s2b_shift;
        return 0;
}

struct block_device_operations
dasd_device_operations = {
        .owner          = THIS_MODULE,
        .open           = dasd_open,
        .release        = dasd_release,
        .ioctl          = dasd_ioctl,
        .compat_ioctl   = dasd_ioctl,
        .getgeo         = dasd_getgeo,
};

/*******************************************************************************
 * end of block device operations
 */

static void
dasd_exit(void)
{
#ifdef CONFIG_PROC_FS
        dasd_proc_exit();
#endif
        dasd_eer_exit();
        if (dasd_page_cache != NULL) {
                kmem_cache_destroy(dasd_page_cache);
                dasd_page_cache = NULL;
        }
        dasd_gendisk_exit();
        dasd_devmap_exit();
        if (dasd_debug_area != NULL) {
                debug_unregister(dasd_debug_area);
                dasd_debug_area = NULL;
        }
}

/*
 * SECTION: common functions for ccw_driver use
 */

/*
 * Initial attempt at a probe function. this can be simplified once
 * the other detection code is gone.
 */
int dasd_generic_probe(struct ccw_device *cdev,
                       struct dasd_discipline *discipline)
{
        int ret;

        ret = ccw_device_set_options(cdev, CCWDEV_DO_PATHGROUP);
        if (ret) {
                DBF_EVENT(DBF_WARNING,
                       "dasd_generic_probe: could not set ccw-device options "
                       "for %s\n", dev_name(&cdev->dev));
                return ret;
        }
        ret = dasd_add_sysfs_files(cdev);
        if (ret) {
                DBF_EVENT(DBF_WARNING,
                       "dasd_generic_probe: could not add sysfs entries "
                       "for %s\n", dev_name(&cdev->dev));
                return ret;
        }
        cdev->handler = &dasd_int_handler;

        /*
         * Automatically online either all dasd devices (dasd_autodetect)
         * or all devices specified with dasd= parameters during
         * initial probe.
         */
        if ((dasd_get_feature(cdev, DASD_FEATURE_INITIAL_ONLINE) > 0 ) ||
            (dasd_autodetect && dasd_busid_known(dev_name(&cdev->dev)) != 0))
                ret = ccw_device_set_online(cdev);
        if (ret)
                pr_warning("%s: Setting the DASD online failed with rc=%d\n",
                       dev_name(&cdev->dev), ret);
        return 0;
}

/*
 * This will one day be called from a global not_oper handler.
 * It is also used by driver_unregister during module unload.
 */
void dasd_generic_remove(struct ccw_device *cdev)
{
        struct dasd_device *device;
        struct dasd_block *block;

        cdev->handler = NULL;

        dasd_remove_sysfs_files(cdev);
        device = dasd_device_from_cdev(cdev);
        if (IS_ERR(device))
                return;
        if (test_and_set_bit(DASD_FLAG_OFFLINE, &device->flags)) {
                /* Already doing offline processing */
                dasd_put_device(device);
                return;
        }
        /*
         * This device is removed unconditionally. Set offline
         * flag to prevent dasd_open from opening it while it is
         * no quite down yet.
         */
        dasd_set_target_state(device, DASD_STATE_NEW);
        /* dasd_delete_device destroys the device reference. */
        block = device->block;
        device->block = NULL;
        dasd_delete_device(device);
        /*
         * life cycle of block is bound to device, so delete it after
         * device was safely removed
         */
        if (block)
                dasd_free_block(block);
}

/*
 * Activate a device. This is called from dasd_{eckd,fba}_probe() when either
 * the device is detected for the first time and is supposed to be used
 * or the user has started activation through sysfs.
 */
int dasd_generic_set_online(struct ccw_device *cdev,
                            struct dasd_discipline *base_discipline)
{
        struct dasd_discipline *discipline;
        struct dasd_device *device;
        int rc;

        /* first online clears initial online feature flag */
        dasd_set_feature(cdev, DASD_FEATURE_INITIAL_ONLINE, 0);
        device = dasd_create_device(cdev);
        if (IS_ERR(device))
                return PTR_ERR(device);

        discipline = base_discipline;
        if (device->features & DASD_FEATURE_USEDIAG) {
                if (!dasd_diag_discipline_pointer) {
                        pr_warning("%s Setting the DASD online failed because "
                                   "of missing DIAG discipline\n",
                                   dev_name(&cdev->dev));
                        dasd_delete_device(device);
                        return -ENODEV;
                }
                discipline = dasd_diag_discipline_pointer;
        }
        if (!try_module_get(base_discipline->owner)) {
                dasd_delete_device(device);
                return -EINVAL;
        }
        if (!try_module_get(discipline->owner)) {
                module_put(base_discipline->owner);
                dasd_delete_device(device);
                return -EINVAL;
        }
        device->base_discipline = base_discipline;
        device->discipline = discipline;

        /* check_device will allocate block device if necessary */
        rc = discipline->check_device(device);
        if (rc) {
                pr_warning("%s Setting the DASD online with discipline %s "
                           "failed with rc=%i\n",
                           dev_name(&cdev->dev), discipline->name, rc);
                module_put(discipline->owner);
                module_put(base_discipline->owner);
                dasd_delete_device(device);
                return rc;
        }

        dasd_set_target_state(device, DASD_STATE_ONLINE);
        if (device->state <= DASD_STATE_KNOWN) {
                pr_warning("%s Setting the DASD online failed because of a "
                           "missing discipline\n", dev_name(&cdev->dev));
                rc = -ENODEV;
                dasd_set_target_state(device, DASD_STATE_NEW);
                if (device->block)
                        dasd_free_block(device->block);
                dasd_delete_device(device);
        } else
                pr_debug("dasd_generic device %s found\n",
                                dev_name(&cdev->dev));

        /* FIXME: we have to wait for the root device but we don't want
         * to wait for each single device but for all at once. */
        wait_event(dasd_init_waitq, _wait_for_device(device));

        dasd_put_device(device);

        return rc;
}

int dasd_generic_set_offline(struct ccw_device *cdev)
{
        struct dasd_device *device;
        struct dasd_block *block;
        int max_count, open_count;

        device = dasd_device_from_cdev(cdev);
        if (IS_ERR(device))
                return PTR_ERR(device);
        if (test_and_set_bit(DASD_FLAG_OFFLINE, &device->flags)) {
                /* Already doing offline processing */
                dasd_put_device(device);
                return 0;
        }
        /*
         * We must make sure that this device is currently not in use.
         * The open_count is increased for every opener, that includes
         * the blkdev_get in dasd_scan_partitions. We are only interested
         * in the other openers.
         */
        if (device->block) {
                max_count = device->block->bdev ? 0 : -1;
                open_count = atomic_read(&device->block->open_count);
                if (open_count > max_count) {
                        if (open_count > 0)
                                pr_warning("%s: The DASD cannot be set offline "
                                           "with open count %i\n",
                                           dev_name(&cdev->dev), open_count);
                        else
                                pr_warning("%s: The DASD cannot be set offline "
                                           "while it is in use\n",
                                           dev_name(&cdev->dev));
                        clear_bit(DASD_FLAG_OFFLINE, &device->flags);
                        dasd_put_device(device);
                        return -EBUSY;
                }
        }
        dasd_set_target_state(device, DASD_STATE_NEW);
        /* dasd_delete_device destroys the device reference. */
        block = device->block;
        device->block = NULL;
        dasd_delete_device(device);
        /*
         * life cycle of block is bound to device, so delete it after
         * device was safely removed
         */
        if (block)
                dasd_free_block(block);
        return 0;
}

int dasd_generic_notify(struct ccw_device *cdev, int event)
{
        struct dasd_device *device;
        struct dasd_ccw_req *cqr;
        int ret;

        device = dasd_device_from_cdev_locked(cdev);
        if (IS_ERR(device))
                return 0;
        ret = 0;
        switch (event) {
        case CIO_GONE:
        case CIO_BOXED:
        case CIO_NO_PATH:
                /* First of all call extended error reporting. */
                dasd_eer_write(device, NULL, DASD_EER_NOPATH);

                if (device->state < DASD_STATE_BASIC)
                        break;
                /* Device is active. We want to keep it. */
                list_for_each_entry(cqr, &device->ccw_queue, devlist)
                        if (cqr->status == DASD_CQR_IN_IO) {
                                cqr->status = DASD_CQR_QUEUED;
                                cqr->retries++;
                        }
                device->stopped |= DASD_STOPPED_DC_WAIT;
                dasd_device_clear_timer(device);
                dasd_schedule_device_bh(device);
                ret = 1;
                break;
        case CIO_OPER:
                /* FIXME: add a sanity check. */
                device->stopped &= ~DASD_STOPPED_DC_WAIT;
                dasd_schedule_device_bh(device);
                if (device->block)
                        dasd_schedule_block_bh(device->block);
                ret = 1;
                break;
        }
        dasd_put_device(device);
        return ret;
}

static struct dasd_ccw_req *dasd_generic_build_rdc(struct dasd_device *device,
                                                   void *rdc_buffer,
                                                   int rdc_buffer_size,
                                                   char *magic)
{
        struct dasd_ccw_req *cqr;
        struct ccw1 *ccw;

        cqr = dasd_smalloc_request(magic, 1 /* RDC */, rdc_buffer_size, device);

        if (IS_ERR(cqr)) {
                /* internal error 13 - Allocating the RDC request failed*/
                dev_err(&device->cdev->dev,
                         "An error occurred in the DASD device driver, "
                         "reason=%s\n", "13");
                return cqr;
        }

        ccw = cqr->cpaddr;
        ccw->cmd_code = CCW_CMD_RDC;
        ccw->cda = (__u32)(addr_t)rdc_buffer;
        ccw->count = rdc_buffer_size;

        cqr->startdev = device;
        cqr->memdev = device;
        cqr->expires = 10*HZ;
        clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
        cqr->retries = 2;
        cqr->buildclk = get_clock();
        cqr->status = DASD_CQR_FILLED;
        return cqr;
}


int dasd_generic_read_dev_chars(struct dasd_device *device, char *magic,
                                void **rdc_buffer, int rdc_buffer_size)
{
        int ret;
        struct dasd_ccw_req *cqr;

        cqr = dasd_generic_build_rdc(device, *rdc_buffer, rdc_buffer_size,
                                     magic);
        if (IS_ERR(cqr))
                return PTR_ERR(cqr);

        ret = dasd_sleep_on(cqr);
        dasd_sfree_request(cqr, cqr->memdev);
        return ret;
}
EXPORT_SYMBOL_GPL(dasd_generic_read_dev_chars);

/*
 *   In command mode and transport mode we need to look for sense
 *   data in different places. The sense data itself is allways
 *   an array of 32 bytes, so we can unify the sense data access
 *   for both modes.
 */
char *dasd_get_sense(struct irb *irb)
{
        struct tsb *tsb = NULL;
        char *sense = NULL;

        if (scsw_is_tm(&irb->scsw) && (irb->scsw.tm.fcxs == 0x01)) {
                if (irb->scsw.tm.tcw)
                        tsb = tcw_get_tsb((struct tcw *)(unsigned long)
                                          irb->scsw.tm.tcw);
                if (tsb && tsb->length == 64 && tsb->flags)
                        switch (tsb->flags & 0x07) {
                        case 1: /* tsa_iostat */
                                sense = tsb->tsa.iostat.sense;
                                break;
                        case 2: /* tsa_ddpc */
                                sense = tsb->tsa.ddpc.sense;
                                break;
                        default:
                                /* currently we don't use interrogate data */
                                break;
                        }
        } else if (irb->esw.esw0.erw.cons) {
                sense = irb->ecw;
        }
        return sense;
}
EXPORT_SYMBOL_GPL(dasd_get_sense);

static int __init dasd_init(void)
{
        int rc;

        init_waitqueue_head(&dasd_init_waitq);
        init_waitqueue_head(&dasd_flush_wq);
        init_waitqueue_head(&generic_waitq);

        /* register 'common' DASD debug area, used for all DBF_XXX calls */
        dasd_debug_area = debug_register("dasd", 1, 1, 8 * sizeof(long));
        if (dasd_debug_area == NULL) {
                rc = -ENOMEM;
                goto failed;
        }
        debug_register_view(dasd_debug_area, &debug_sprintf_view);
        debug_set_level(dasd_debug_area, DBF_WARNING);

        DBF_EVENT(DBF_EMERG, "%s", "debug area created");

        dasd_diag_discipline_pointer = NULL;

        rc = dasd_devmap_init();
        if (rc)
                goto failed;
        rc = dasd_gendisk_init();
        if (rc)
                goto failed;
        rc = dasd_parse();
        if (rc)
                goto failed;
        rc = dasd_eer_init();
        if (rc)
                goto failed;
#ifdef CONFIG_PROC_FS
        rc = dasd_proc_init();
        if (rc)
                goto failed;
#endif

        return 0;
failed:
        pr_info("The DASD device driver could not be initialized\n");
        dasd_exit();
        return rc;
}

module_init(dasd_init);
module_exit(dasd_exit);

EXPORT_SYMBOL(dasd_debug_area);
EXPORT_SYMBOL(dasd_diag_discipline_pointer);

EXPORT_SYMBOL(dasd_add_request_head);
EXPORT_SYMBOL(dasd_add_request_tail);
EXPORT_SYMBOL(dasd_cancel_req);
EXPORT_SYMBOL(dasd_device_clear_timer);
EXPORT_SYMBOL(dasd_block_clear_timer);
EXPORT_SYMBOL(dasd_enable_device);
EXPORT_SYMBOL(dasd_int_handler);
EXPORT_SYMBOL(dasd_kfree_request);
EXPORT_SYMBOL(dasd_kick_device);
EXPORT_SYMBOL(dasd_kmalloc_request);
EXPORT_SYMBOL(dasd_schedule_device_bh);
EXPORT_SYMBOL(dasd_schedule_block_bh);
EXPORT_SYMBOL(dasd_set_target_state);
EXPORT_SYMBOL(dasd_device_set_timer);
EXPORT_SYMBOL(dasd_block_set_timer);
EXPORT_SYMBOL(dasd_sfree_request);
EXPORT_SYMBOL(dasd_sleep_on);
EXPORT_SYMBOL(dasd_sleep_on_immediatly);
EXPORT_SYMBOL(dasd_sleep_on_interruptible);
EXPORT_SYMBOL(dasd_smalloc_request);
EXPORT_SYMBOL(dasd_start_IO);
EXPORT_SYMBOL(dasd_term_IO);

EXPORT_SYMBOL_GPL(dasd_generic_probe);
EXPORT_SYMBOL_GPL(dasd_generic_remove);
EXPORT_SYMBOL_GPL(dasd_generic_notify);
EXPORT_SYMBOL_GPL(dasd_generic_set_online);
EXPORT_SYMBOL_GPL(dasd_generic_set_offline);
EXPORT_SYMBOL_GPL(dasd_generic_handle_state_change);
EXPORT_SYMBOL_GPL(dasd_flush_device_queue);
EXPORT_SYMBOL_GPL(dasd_alloc_block);
EXPORT_SYMBOL_GPL(dasd_free_block);