/*
 *  drivers/s390/char/tape_block.c
 *    block device frontend for tape device driver
 *
 *  S390 and zSeries version
 *    Copyright (C) 2001,2003 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Carsten Otte <cotte@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"

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/buffer_head.h>
#include <linux/kernel.h>

#include <asm/debug.h>

#define TAPE_DBF_AREA   tape_core_dbf

#include "tape.h"

#define TAPEBLOCK_MAX_SEC       100
#define TAPEBLOCK_MIN_REQUEUE   3

/*
 * 2003/11/25  Stefan Bader <shbader@de.ibm.com>
 *
 * In 2.5/2.6 the block device request function is very likely to be called
 * with disabled interrupts (e.g. generic_unplug_device). So the driver can't
 * just call any function that tries to allocate CCW requests from that con-
 * text since it might sleep. There are two choices to work around this:
 *      a) do not allocate with kmalloc but use its own memory pool
 *      b) take requests from the queue outside that context, knowing that
 *         allocation might sleep
 */

/*
 * file operation structure for tape block frontend
 */
static int tapeblock_open(struct block_device *, fmode_t);
static int tapeblock_release(struct gendisk *, fmode_t);
static int tapeblock_ioctl(struct block_device *, fmode_t, unsigned int,
                                unsigned long);
static int tapeblock_medium_changed(struct gendisk *);
static int tapeblock_revalidate_disk(struct gendisk *);

static struct block_device_operations tapeblock_fops = {
        .owner           = THIS_MODULE,
        .open            = tapeblock_open,
        .release         = tapeblock_release,
        .locked_ioctl           = tapeblock_ioctl,
        .media_changed   = tapeblock_medium_changed,
        .revalidate_disk = tapeblock_revalidate_disk,
};

static int tapeblock_major = 0;

static void
tapeblock_trigger_requeue(struct tape_device *device)
{
        /* Protect against rescheduling. */
        if (atomic_cmpxchg(&device->blk_data.requeue_scheduled, 0, 1) != 0)
                return;
        schedule_work(&device->blk_data.requeue_task);
}

/*
 * Post finished request.
 */
static void
tapeblock_end_request(struct request *req, int error)
{
        if (blk_end_request(req, error, blk_rq_bytes(req)))
                BUG();
}

static void
__tapeblock_end_request(struct tape_request *ccw_req, void *data)
{
        struct tape_device *device;
        struct request *req;

        DBF_LH(6, "__tapeblock_end_request()\n");

        device = ccw_req->device;
        req = (struct request *) data;
        tapeblock_end_request(req, (ccw_req->rc == 0) ? 0 : -EIO);
        if (ccw_req->rc == 0)
                /* Update position. */
                device->blk_data.block_position =
                        (req->sector + req->nr_sectors) >> TAPEBLOCK_HSEC_S2B;
        else
                /* We lost the position information due to an error. */
                device->blk_data.block_position = -1;
        device->discipline->free_bread(ccw_req);
        if (!list_empty(&device->req_queue) ||
            elv_next_request(device->blk_data.request_queue))
                tapeblock_trigger_requeue(device);
}

/*
 * Feed the tape device CCW queue with requests supplied in a list.
 */
static int
tapeblock_start_request(struct tape_device *device, struct request *req)
{
        struct tape_request *   ccw_req;
        int                     rc;

        DBF_LH(6, "tapeblock_start_request(%p, %p)\n", device, req);

        ccw_req = device->discipline->bread(device, req);
        if (IS_ERR(ccw_req)) {
                DBF_EVENT(1, "TBLOCK: bread failed\n");
                tapeblock_end_request(req, -EIO);
                return PTR_ERR(ccw_req);
        }
        ccw_req->callback = __tapeblock_end_request;
        ccw_req->callback_data = (void *) req;
        ccw_req->retries = TAPEBLOCK_RETRIES;

        rc = tape_do_io_async(device, ccw_req);
        if (rc) {
                /*
                 * Start/enqueueing failed. No retries in
                 * this case.
                 */
                tapeblock_end_request(req, -EIO);
                device->discipline->free_bread(ccw_req);
        }

        return rc;
}

/*
 * Move requests from the block device request queue to the tape device ccw
 * queue.
 */
static void
tapeblock_requeue(struct work_struct *work) {
        struct tape_blk_data *  blkdat;
        struct tape_device *    device;
        struct request_queue *  queue;
        int                     nr_queued;
        struct request *        req;
        struct list_head *      l;
        int                     rc;

        blkdat = container_of(work, struct tape_blk_data, requeue_task);
        device = blkdat->device;
        if (!device)
                return;

        spin_lock_irq(get_ccwdev_lock(device->cdev));
        queue  = device->blk_data.request_queue;

        /* Count number of requests on ccw queue. */
        nr_queued = 0;
        list_for_each(l, &device->req_queue)
                nr_queued++;
        spin_unlock(get_ccwdev_lock(device->cdev));

        spin_lock_irq(&device->blk_data.request_queue_lock);
        while (
                !blk_queue_plugged(queue) &&
                elv_next_request(queue)   &&
                nr_queued < TAPEBLOCK_MIN_REQUEUE
        ) {
                req = elv_next_request(queue);
                if (rq_data_dir(req) == WRITE) {
                        DBF_EVENT(1, "TBLOCK: Rejecting write request\n");
                        blkdev_dequeue_request(req);
                        spin_unlock_irq(&device->blk_data.request_queue_lock);
                        tapeblock_end_request(req, -EIO);
                        spin_lock_irq(&device->blk_data.request_queue_lock);
                        continue;
                }
                blkdev_dequeue_request(req);
                nr_queued++;
                spin_unlock_irq(&device->blk_data.request_queue_lock);
                rc = tapeblock_start_request(device, req);
                spin_lock_irq(&device->blk_data.request_queue_lock);
        }
        spin_unlock_irq(&device->blk_data.request_queue_lock);
        atomic_set(&device->blk_data.requeue_scheduled, 0);
}

/*
 * Tape request queue function. Called from ll_rw_blk.c
 */
static void
tapeblock_request_fn(struct request_queue *queue)
{
        struct tape_device *device;

        device = (struct tape_device *) queue->queuedata;
        DBF_LH(6, "tapeblock_request_fn(device=%p)\n", device);
        BUG_ON(device == NULL);
        tapeblock_trigger_requeue(device);
}

/*
 * This function is called for every new tapedevice
 */
int
tapeblock_setup_device(struct tape_device * device)
{
        struct tape_blk_data *  blkdat;
        struct gendisk *        disk;
        int                     rc;

        blkdat = &device->blk_data;
        blkdat->device = device;
        spin_lock_init(&blkdat->request_queue_lock);
        atomic_set(&blkdat->requeue_scheduled, 0);

        blkdat->request_queue = blk_init_queue(
                tapeblock_request_fn,
                &blkdat->request_queue_lock
        );
        if (!blkdat->request_queue)
                return -ENOMEM;

        elevator_exit(blkdat->request_queue->elevator);
        rc = elevator_init(blkdat->request_queue, "noop");
        if (rc)
                goto cleanup_queue;

        blk_queue_hardsect_size(blkdat->request_queue, TAPEBLOCK_HSEC_SIZE);
        blk_queue_max_sectors(blkdat->request_queue, TAPEBLOCK_MAX_SEC);
        blk_queue_max_phys_segments(blkdat->request_queue, -1L);
        blk_queue_max_hw_segments(blkdat->request_queue, -1L);
        blk_queue_max_segment_size(blkdat->request_queue, -1L);
        blk_queue_segment_boundary(blkdat->request_queue, -1L);

        disk = alloc_disk(1);
        if (!disk) {
                rc = -ENOMEM;
                goto cleanup_queue;
        }

        disk->major = tapeblock_major;
        disk->first_minor = device->first_minor;
        disk->fops = &tapeblock_fops;
        disk->private_data = tape_get_device_reference(device);
        disk->queue = blkdat->request_queue;
        set_capacity(disk, 0);
        sprintf(disk->disk_name, "btibm%d",
                device->first_minor / TAPE_MINORS_PER_DEV);

        blkdat->disk = disk;
        blkdat->medium_changed = 1;
        blkdat->request_queue->queuedata = tape_get_device_reference(device);

        add_disk(disk);

        tape_get_device_reference(device);
        INIT_WORK(&blkdat->requeue_task, tapeblock_requeue);

        return 0;

cleanup_queue:
        blk_cleanup_queue(blkdat->request_queue);
        blkdat->request_queue = NULL;

        return rc;
}

void
tapeblock_cleanup_device(struct tape_device *device)
{
        flush_scheduled_work();
        tape_put_device(device);

        if (!device->blk_data.disk) {
                goto cleanup_queue;
        }

        del_gendisk(device->blk_data.disk);
        device->blk_data.disk->private_data =
                tape_put_device(device->blk_data.disk->private_data);
        put_disk(device->blk_data.disk);

        device->blk_data.disk = NULL;
cleanup_queue:
        device->blk_data.request_queue->queuedata = tape_put_device(device);

        blk_cleanup_queue(device->blk_data.request_queue);
        device->blk_data.request_queue = NULL;
}

/*
 * Detect number of blocks of the tape.
 * FIXME: can we extent this to detect the blocks size as well ?
 */
static int
tapeblock_revalidate_disk(struct gendisk *disk)
{
        struct tape_device *    device;
        unsigned int            nr_of_blks;
        int                     rc;

        device = (struct tape_device *) disk->private_data;
        BUG_ON(!device);

        if (!device->blk_data.medium_changed)
                return 0;

        dev_info(&device->cdev->dev, "Determining the size of the recorded "
                "area...\n");
        rc = tape_mtop(device, MTFSFM, 1);
        if (rc)
                return rc;

        rc = tape_mtop(device, MTTELL, 1);
        if (rc < 0)
                return rc;

        DBF_LH(3, "Image file ends at %d\n", rc);
        nr_of_blks = rc;

        /* This will fail for the first file. Catch the error by checking the
         * position. */
        tape_mtop(device, MTBSF, 1);

        rc = tape_mtop(device, MTTELL, 1);
        if (rc < 0)
                return rc;

        if (rc > nr_of_blks)
                return -EINVAL;

        DBF_LH(3, "Image file starts at %d\n", rc);
        device->bof = rc;
        nr_of_blks -= rc;

        dev_info(&device->cdev->dev, "The size of the recorded area is %i "
                "blocks\n", nr_of_blks);
        set_capacity(device->blk_data.disk,
                nr_of_blks*(TAPEBLOCK_HSEC_SIZE/512));

        device->blk_data.block_position = 0;
        device->blk_data.medium_changed = 0;
        return 0;
}

static int
tapeblock_medium_changed(struct gendisk *disk)
{
        struct tape_device *device;

        device = (struct tape_device *) disk->private_data;
        DBF_LH(6, "tapeblock_medium_changed(%p) = %d\n",
                device, device->blk_data.medium_changed);

        return device->blk_data.medium_changed;
}

/*
 * Block frontend tape device open function.
 */
static int
tapeblock_open(struct block_device *bdev, fmode_t mode)
{
        struct gendisk *        disk = bdev->bd_disk;
        struct tape_device *    device;
        int                     rc;

        device = tape_get_device_reference(disk->private_data);

        if (device->required_tapemarks) {
                DBF_EVENT(2, "TBLOCK: missing tapemarks\n");
                dev_warn(&device->cdev->dev, "Opening the tape failed because"
                        " of missing end-of-file marks\n");
                rc = -EPERM;
                goto put_device;
        }

        rc = tape_open(device);
        if (rc)
                goto put_device;

        rc = tapeblock_revalidate_disk(disk);
        if (rc)
                goto release;

        /*
         * Note: The reference to <device> is hold until the release function
         *       is called.
         */
        tape_state_set(device, TS_BLKUSE);
        return 0;

release:
        tape_release(device);
 put_device:
        tape_put_device(device);
        return rc;
}

/*
 * Block frontend tape device release function.
 *
 * Note: One reference to the tape device was made by the open function. So
 *       we just get the pointer here and release the reference.
 */
static int
tapeblock_release(struct gendisk *disk, fmode_t mode)
{
        struct tape_device *device = disk->private_data;

        tape_state_set(device, TS_IN_USE);
        tape_release(device);
        tape_put_device(device);

        return 0;
}

/*
 * Support of some generic block device IOCTLs.
 */
static int
tapeblock_ioctl(
        struct block_device *   bdev,
        fmode_t                 mode,
        unsigned int            command,
        unsigned long           arg
) {
        int rc;
        int minor;
        struct gendisk *disk = bdev->bd_disk;
        struct tape_device *device;

        rc     = 0;
        BUG_ON(!disk);
        device = disk->private_data;
        BUG_ON(!device);
        minor  = MINOR(bdev->bd_dev);

        DBF_LH(6, "tapeblock_ioctl(0x%0x)\n", command);
        DBF_LH(6, "device = %d:%d\n", tapeblock_major, minor);

        switch (command) {
                /* Refuse some IOCTL calls without complaining (mount). */
                case 0x5310:            /* CDROMMULTISESSION */
                        rc = -EINVAL;
                        break;
                default:
                        rc = -EINVAL;
        }

        return rc;
}

/*
 * Initialize block device frontend.
 */
int
tapeblock_init(void)
{
        int rc;

        /* Register the tape major number to the kernel */
        rc = register_blkdev(tapeblock_major, "tBLK");
        if (rc < 0)
                return rc;

        if (tapeblock_major == 0)
                tapeblock_major = rc;
        return 0;
}

/*
 * Deregister major for block device frontend
 */
void
tapeblock_exit(void)
{
        unregister_blkdev(tapeblock_major, "tBLK");
}