/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place - Suite 330, Boston, MA 02111-1307 USA.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/blkdev.h>
#include <linux/major.h>
#include <linux/delay.h>
#include <linux/hdreg.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_dbg.h>
#include "osd.h"
#include "logging.h"
#include "vmbus.h"
#include "StorVscApi.h"


#define BLKVSC_MINORS   64

enum blkvsc_device_type {
        UNKNOWN_DEV_TYPE,
        HARDDISK_TYPE,
        DVD_TYPE,
};

/*
 * This request ties the struct request and struct
 * blkvsc_request/hv_storvsc_request together A struct request may be
 * represented by 1 or more struct blkvsc_request
 */
struct blkvsc_request_group {
        int outstanding;
        int status;
        struct list_head blkvsc_req_list;       /* list of blkvsc_requests */
};

struct blkvsc_request {
        /* blkvsc_request_group.blkvsc_req_list */
        struct list_head req_entry;

        /* block_device_context.pending_list */
        struct list_head pend_entry;

        /* This may be null if we generate a request internally */
        struct request *req;

        struct block_device_context *dev;

        /* The group this request is part of. Maybe null */
        struct blkvsc_request_group *group;

        wait_queue_head_t wevent;
        int cond;

        int write;
        sector_t sector_start;
        unsigned long sector_count;

        unsigned char sense_buffer[SCSI_SENSE_BUFFERSIZE];
        unsigned char cmd_len;
        unsigned char cmnd[MAX_COMMAND_SIZE];

        struct hv_storvsc_request request;
        /*
         * !!!DO NOT ADD ANYTHING BELOW HERE!!! Otherwise, memory can overlap,
         * because - The extension buffer falls right here and is pointed to by
         * request.Extension;
         * Which sounds like a horrible idea, who designed this?
         */
};

/* Per device structure */
struct block_device_context {
        /* point back to our device context */
        struct device_context *device_ctx;
        struct kmem_cache *request_pool;
        spinlock_t lock;
        struct gendisk *gd;
        enum blkvsc_device_type device_type;
        struct list_head pending_list;

        unsigned char device_id[64];
        unsigned int device_id_len;
        int num_outstanding_reqs;
        int shutting_down;
        int media_not_present;
        unsigned int sector_size;
        sector_t capacity;
        unsigned int port;
        unsigned char path;
        unsigned char target;
        int users;
};

/* Per driver */
struct blkvsc_driver_context {
        /* !! These must be the first 2 fields !! */
        /* FIXME this is a bug! */
        struct driver_context drv_ctx;
        struct storvsc_driver_object drv_obj;
};

/* Static decl */
static int blkvsc_probe(struct device *dev);
static int blkvsc_remove(struct device *device);
static void blkvsc_shutdown(struct device *device);

static int blkvsc_open(struct block_device *bdev,  fmode_t mode);
static int blkvsc_release(struct gendisk *disk, fmode_t mode);
static int blkvsc_media_changed(struct gendisk *gd);
static int blkvsc_revalidate_disk(struct gendisk *gd);
static int blkvsc_getgeo(struct block_device *bd, struct hd_geometry *hg);
static int blkvsc_ioctl(struct block_device *bd, fmode_t mode,
                        unsigned cmd, unsigned long argument);
static void blkvsc_request(struct request_queue *queue);
static void blkvsc_request_completion(struct hv_storvsc_request *request);
static int blkvsc_do_request(struct block_device_context *blkdev,
                             struct request *req);
static int blkvsc_submit_request(struct blkvsc_request *blkvsc_req,
                void (*request_completion)(struct hv_storvsc_request *));
static void blkvsc_init_rw(struct blkvsc_request *blkvsc_req);
static void blkvsc_cmd_completion(struct hv_storvsc_request *request);
static int blkvsc_do_inquiry(struct block_device_context *blkdev);
static int blkvsc_do_read_capacity(struct block_device_context *blkdev);
static int blkvsc_do_read_capacity16(struct block_device_context *blkdev);
static int blkvsc_do_flush(struct block_device_context *blkdev);
static int blkvsc_cancel_pending_reqs(struct block_device_context *blkdev);
static int blkvsc_do_pending_reqs(struct block_device_context *blkdev);


static int blkvsc_ringbuffer_size = BLKVSC_RING_BUFFER_SIZE;

/* The one and only one */
static struct blkvsc_driver_context g_blkvsc_drv;

static struct block_device_operations block_ops = {
        .owner = THIS_MODULE,
        .open = blkvsc_open,
        .release = blkvsc_release,
        .media_changed = blkvsc_media_changed,
        .revalidate_disk = blkvsc_revalidate_disk,
        .getgeo = blkvsc_getgeo,
        .ioctl  = blkvsc_ioctl,
};

/**
 * blkvsc_drv_init -  BlkVsc driver initialization.
 */
static int blkvsc_drv_init(int (*drv_init)(struct hv_driver *drv))
{
        struct storvsc_driver_object *storvsc_drv_obj = &g_blkvsc_drv.drv_obj;
        struct driver_context *drv_ctx = &g_blkvsc_drv.drv_ctx;
        int ret;

        DPRINT_ENTER(BLKVSC_DRV);

        vmbus_get_interface(&storvsc_drv_obj->Base.VmbusChannelInterface);

        storvsc_drv_obj->RingBufferSize = blkvsc_ringbuffer_size;

        /* Callback to client driver to complete the initialization */
        drv_init(&storvsc_drv_obj->Base);

        drv_ctx->driver.name = storvsc_drv_obj->Base.name;
        memcpy(&drv_ctx->class_id, &storvsc_drv_obj->Base.deviceType,
               sizeof(struct hv_guid));

        drv_ctx->probe = blkvsc_probe;
        drv_ctx->remove = blkvsc_remove;
        drv_ctx->shutdown = blkvsc_shutdown;

        /* The driver belongs to vmbus */
        ret = vmbus_child_driver_register(drv_ctx);

        DPRINT_EXIT(BLKVSC_DRV);

        return ret;
}

static int blkvsc_drv_exit_cb(struct device *dev, void *data)
{
        struct device **curr = (struct device **)data;
        *curr = dev;
        return 1; /* stop iterating */
}

static void blkvsc_drv_exit(void)
{
        struct storvsc_driver_object *storvsc_drv_obj = &g_blkvsc_drv.drv_obj;
        struct driver_context *drv_ctx = &g_blkvsc_drv.drv_ctx;
        struct device *current_dev;
        int ret;

        DPRINT_ENTER(BLKVSC_DRV);

        while (1) {
                current_dev = NULL;

                /* Get the device */
                ret = driver_for_each_device(&drv_ctx->driver, NULL,
                                             (void *) &current_dev,
                                             blkvsc_drv_exit_cb);

                if (ret)
                        DPRINT_WARN(BLKVSC_DRV,
                                    "driver_for_each_device returned %d", ret);


                if (current_dev == NULL)
                        break;

                /* Initiate removal from the top-down */
                device_unregister(current_dev);
        }

        if (storvsc_drv_obj->Base.OnCleanup)
                storvsc_drv_obj->Base.OnCleanup(&storvsc_drv_obj->Base);

        vmbus_child_driver_unregister(drv_ctx);

        DPRINT_EXIT(BLKVSC_DRV);

        return;
}

/**
 * blkvsc_probe - Add a new device for this driver
 */
static int blkvsc_probe(struct device *device)
{
        struct driver_context *driver_ctx =
                                driver_to_driver_context(device->driver);
        struct blkvsc_driver_context *blkvsc_drv_ctx =
                                (struct blkvsc_driver_context *)driver_ctx;
        struct storvsc_driver_object *storvsc_drv_obj =
                                &blkvsc_drv_ctx->drv_obj;
        struct device_context *device_ctx = device_to_device_context(device);
        struct hv_device *device_obj = &device_ctx->device_obj;

        struct block_device_context *blkdev = NULL;
        struct storvsc_device_info device_info;
        int major = 0;
        int devnum = 0;
        int ret = 0;
        static int ide0_registered;
        static int ide1_registered;

        DPRINT_ENTER(BLKVSC_DRV);

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_probe - enter");

        if (!storvsc_drv_obj->Base.OnDeviceAdd) {
                DPRINT_ERR(BLKVSC_DRV, "OnDeviceAdd() not set");
                ret = -1;
                goto Cleanup;
        }

        blkdev = kzalloc(sizeof(struct block_device_context), GFP_KERNEL);
        if (!blkdev) {
                ret = -ENOMEM;
                goto Cleanup;
        }

        INIT_LIST_HEAD(&blkdev->pending_list);

        /* Initialize what we can here */
        spin_lock_init(&blkdev->lock);

        ASSERT(sizeof(struct blkvsc_request_group) <=
                sizeof(struct blkvsc_request));

        blkdev->request_pool = kmem_cache_create(dev_name(&device_ctx->device),
                                        sizeof(struct blkvsc_request) +
                                        storvsc_drv_obj->RequestExtSize, 0,
                                        SLAB_HWCACHE_ALIGN, NULL);
        if (!blkdev->request_pool) {
                ret = -ENOMEM;
                goto Cleanup;
        }


        /* Call to the vsc driver to add the device */
        ret = storvsc_drv_obj->Base.OnDeviceAdd(device_obj, &device_info);
        if (ret != 0) {
                DPRINT_ERR(BLKVSC_DRV, "unable to add blkvsc device");
                goto Cleanup;
        }

        blkdev->device_ctx = device_ctx;
        /* this identified the device 0 or 1 */
        blkdev->target = device_info.TargetId;
        /* this identified the ide ctrl 0 or 1 */
        blkdev->path = device_info.PathId;

        dev_set_drvdata(device, blkdev);

        /* Calculate the major and device num */
        if (blkdev->path == 0) {
                major = IDE0_MAJOR;
                devnum = blkdev->path + blkdev->target;         /* 0 or 1 */

                if (!ide0_registered) {
                        ret = register_blkdev(major, "ide");
                        if (ret != 0) {
                                DPRINT_ERR(BLKVSC_DRV,
                                           "register_blkdev() failed! ret %d",
                                           ret);
                                goto Remove;
                        }

                        ide0_registered = 1;
                }
        } else if (blkdev->path == 1) {
                major = IDE1_MAJOR;
                devnum = blkdev->path + blkdev->target + 1; /* 2 or 3 */

                if (!ide1_registered) {
                        ret = register_blkdev(major, "ide");
                        if (ret != 0) {
                                DPRINT_ERR(BLKVSC_DRV,
                                           "register_blkdev() failed! ret %d",
                                           ret);
                                goto Remove;
                        }

                        ide1_registered = 1;
                }
        } else {
                DPRINT_ERR(BLKVSC_DRV, "invalid pathid");
                ret = -1;
                goto Cleanup;
        }

        DPRINT_INFO(BLKVSC_DRV, "blkvsc registered for major %d!!", major);

        blkdev->gd = alloc_disk(BLKVSC_MINORS);
        if (!blkdev->gd) {
                DPRINT_ERR(BLKVSC_DRV, "register_blkdev() failed! ret %d", ret);
                ret = -1;
                goto Cleanup;
        }

        blkdev->gd->queue = blk_init_queue(blkvsc_request, &blkdev->lock);

        blk_queue_max_segment_size(blkdev->gd->queue, PAGE_SIZE);
        blk_queue_max_phys_segments(blkdev->gd->queue,
                                    MAX_MULTIPAGE_BUFFER_COUNT);
        blk_queue_max_hw_segments(blkdev->gd->queue,
                                  MAX_MULTIPAGE_BUFFER_COUNT);
        blk_queue_segment_boundary(blkdev->gd->queue, PAGE_SIZE-1);
        blk_queue_bounce_limit(blkdev->gd->queue, BLK_BOUNCE_ANY);
        blk_queue_dma_alignment(blkdev->gd->queue, 511);

        blkdev->gd->major = major;
        if (devnum == 1 || devnum == 3)
                blkdev->gd->first_minor = BLKVSC_MINORS;
        else
                blkdev->gd->first_minor = 0;
        blkdev->gd->fops = &block_ops;
        blkdev->gd->private_data = blkdev;
        sprintf(blkdev->gd->disk_name, "hd%c", 'a' + devnum);

        blkvsc_do_inquiry(blkdev);
        if (blkdev->device_type == DVD_TYPE) {
                set_disk_ro(blkdev->gd, 1);
                blkdev->gd->flags |= GENHD_FL_REMOVABLE;
                blkvsc_do_read_capacity(blkdev);
        } else {
                blkvsc_do_read_capacity16(blkdev);
        }

        set_capacity(blkdev->gd, blkdev->capacity * (blkdev->sector_size/512));
        blk_queue_logical_block_size(blkdev->gd->queue, blkdev->sector_size);
        /* go! */
        add_disk(blkdev->gd);

        DPRINT_INFO(BLKVSC_DRV, "%s added!! capacity %lu sector_size %d",
                    blkdev->gd->disk_name, (unsigned long)blkdev->capacity,
                    blkdev->sector_size);

        return ret;

Remove:
        storvsc_drv_obj->Base.OnDeviceRemove(device_obj);

Cleanup:
        if (blkdev) {
                if (blkdev->request_pool) {
                        kmem_cache_destroy(blkdev->request_pool);
                        blkdev->request_pool = NULL;
                }
                kfree(blkdev);
                blkdev = NULL;
        }

        DPRINT_EXIT(BLKVSC_DRV);

        return ret;
}

static void blkvsc_shutdown(struct device *device)
{
        struct block_device_context *blkdev = dev_get_drvdata(device);
        unsigned long flags;

        if (!blkdev)
                return;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_shutdown - users %d disk %s\n",
                   blkdev->users, blkdev->gd->disk_name);

        spin_lock_irqsave(&blkdev->lock, flags);

        blkdev->shutting_down = 1;

        blk_stop_queue(blkdev->gd->queue);

        spin_unlock_irqrestore(&blkdev->lock, flags);

        while (blkdev->num_outstanding_reqs) {
                DPRINT_INFO(STORVSC, "waiting for %d requests to complete...",
                            blkdev->num_outstanding_reqs);
                udelay(100);
        }

        blkvsc_do_flush(blkdev);

        spin_lock_irqsave(&blkdev->lock, flags);

        blkvsc_cancel_pending_reqs(blkdev);

        spin_unlock_irqrestore(&blkdev->lock, flags);
}

static int blkvsc_do_flush(struct block_device_context *blkdev)
{
        struct blkvsc_request *blkvsc_req;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_do_flush()\n");

        if (blkdev->device_type != HARDDISK_TYPE)
                return 0;

        blkvsc_req = kmem_cache_alloc(blkdev->request_pool, GFP_KERNEL);
        if (!blkvsc_req)
                return -ENOMEM;

        memset(blkvsc_req, 0, sizeof(struct blkvsc_request));
        init_waitqueue_head(&blkvsc_req->wevent);
        blkvsc_req->dev = blkdev;
        blkvsc_req->req = NULL;
        blkvsc_req->write = 0;

        blkvsc_req->request.DataBuffer.PfnArray[0] = 0;
        blkvsc_req->request.DataBuffer.Offset = 0;
        blkvsc_req->request.DataBuffer.Length = 0;

        blkvsc_req->cmnd[0] = SYNCHRONIZE_CACHE;
        blkvsc_req->cmd_len = 10;

        /*
         * Set this here since the completion routine may be invoked and
         * completed before we return
         */
        blkvsc_req->cond = 0;
        blkvsc_submit_request(blkvsc_req, blkvsc_cmd_completion);

        wait_event_interruptible(blkvsc_req->wevent, blkvsc_req->cond);

        kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);

        return 0;
}

/* Do a scsi INQUIRY cmd here to get the device type (ie disk or dvd) */
static int blkvsc_do_inquiry(struct block_device_context *blkdev)
{
        struct blkvsc_request *blkvsc_req;
        struct page *page_buf;
        unsigned char *buf;
        unsigned char device_type;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_do_inquiry()\n");

        blkvsc_req = kmem_cache_alloc(blkdev->request_pool, GFP_KERNEL);
        if (!blkvsc_req)
                return -ENOMEM;

        memset(blkvsc_req, 0, sizeof(struct blkvsc_request));
        page_buf = alloc_page(GFP_KERNEL);
        if (!page_buf) {
                kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);
                return -ENOMEM;
        }

        init_waitqueue_head(&blkvsc_req->wevent);
        blkvsc_req->dev = blkdev;
        blkvsc_req->req = NULL;
        blkvsc_req->write = 0;

        blkvsc_req->request.DataBuffer.PfnArray[0] = page_to_pfn(page_buf);
        blkvsc_req->request.DataBuffer.Offset = 0;
        blkvsc_req->request.DataBuffer.Length = 64;

        blkvsc_req->cmnd[0] = INQUIRY;
        blkvsc_req->cmnd[1] = 0x1;              /* Get product data */
        blkvsc_req->cmnd[2] = 0x83;             /* mode page 83 */
        blkvsc_req->cmnd[4] = 64;
        blkvsc_req->cmd_len = 6;

        /*
         * Set this here since the completion routine may be invoked and
         * completed before we return
         */
        blkvsc_req->cond = 0;

        blkvsc_submit_request(blkvsc_req, blkvsc_cmd_completion);

        DPRINT_DBG(BLKVSC_DRV, "waiting %p to complete - cond %d\n",
                   blkvsc_req, blkvsc_req->cond);

        wait_event_interruptible(blkvsc_req->wevent, blkvsc_req->cond);

        buf = kmap(page_buf);

        /* print_hex_dump_bytes("", DUMP_PREFIX_NONE, buf, 64); */
        /* be to le */
        device_type = buf[0] & 0x1F;

        if (device_type == 0x0) {
                blkdev->device_type = HARDDISK_TYPE;
        } else if (device_type == 0x5) {
                blkdev->device_type = DVD_TYPE;
        } else {
                /* TODO: this is currently unsupported device type */
                blkdev->device_type = UNKNOWN_DEV_TYPE;
        }

        DPRINT_DBG(BLKVSC_DRV, "device type %d \n", device_type);

        blkdev->device_id_len = buf[7];
        if (blkdev->device_id_len > 64)
                blkdev->device_id_len = 64;

        memcpy(blkdev->device_id, &buf[8], blkdev->device_id_len);
        /* printk_hex_dump_bytes("", DUMP_PREFIX_NONE, blkdev->device_id,
         * blkdev->device_id_len); */

        kunmap(page_buf);

        __free_page(page_buf);

        kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);

        return 0;
}

/* Do a scsi READ_CAPACITY cmd here to get the size of the disk */
static int blkvsc_do_read_capacity(struct block_device_context *blkdev)
{
        struct blkvsc_request *blkvsc_req;
        struct page *page_buf;
        unsigned char *buf;
        struct scsi_sense_hdr sense_hdr;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_do_read_capacity()\n");

        blkdev->sector_size = 0;
        blkdev->capacity = 0;
        blkdev->media_not_present = 0; /* assume a disk is present */

        blkvsc_req = kmem_cache_alloc(blkdev->request_pool, GFP_KERNEL);
        if (!blkvsc_req)
                return -ENOMEM;

        memset(blkvsc_req, 0, sizeof(struct blkvsc_request));
        page_buf = alloc_page(GFP_KERNEL);
        if (!page_buf) {
                kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);
                return -ENOMEM;
        }

        init_waitqueue_head(&blkvsc_req->wevent);
        blkvsc_req->dev = blkdev;
        blkvsc_req->req = NULL;
        blkvsc_req->write = 0;

        blkvsc_req->request.DataBuffer.PfnArray[0] = page_to_pfn(page_buf);
        blkvsc_req->request.DataBuffer.Offset = 0;
        blkvsc_req->request.DataBuffer.Length = 8;

        blkvsc_req->cmnd[0] = READ_CAPACITY;
        blkvsc_req->cmd_len = 16;

        /*
         * Set this here since the completion routine may be invoked
         * and completed before we return
         */
        blkvsc_req->cond = 0;

        blkvsc_submit_request(blkvsc_req, blkvsc_cmd_completion);

        DPRINT_DBG(BLKVSC_DRV, "waiting %p to complete - cond %d\n",
                   blkvsc_req, blkvsc_req->cond);

        wait_event_interruptible(blkvsc_req->wevent, blkvsc_req->cond);

        /* check error */
        if (blkvsc_req->request.Status) {
                scsi_normalize_sense(blkvsc_req->sense_buffer,
                                     SCSI_SENSE_BUFFERSIZE, &sense_hdr);

                if (sense_hdr.asc == 0x3A) {
                        /* Medium not present */
                        blkdev->media_not_present = 1;
                }
                return 0;
        }
        buf = kmap(page_buf);

        /* be to le */
        blkdev->capacity = ((buf[0] << 24) | (buf[1] << 16) |
                            (buf[2] << 8) | buf[3]) + 1;
        blkdev->sector_size = (buf[4] << 24) | (buf[5] << 16) |
                              (buf[6] << 8) | buf[7];

        kunmap(page_buf);

        __free_page(page_buf);

        kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);

        return 0;
}

static int blkvsc_do_read_capacity16(struct block_device_context *blkdev)
{
        struct blkvsc_request *blkvsc_req;
        struct page *page_buf;
        unsigned char *buf;
        struct scsi_sense_hdr sense_hdr;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_do_read_capacity16()\n");

        blkdev->sector_size = 0;
        blkdev->capacity = 0;
        blkdev->media_not_present = 0; /* assume a disk is present */

        blkvsc_req = kmem_cache_alloc(blkdev->request_pool, GFP_KERNEL);
        if (!blkvsc_req)
                return -ENOMEM;

        memset(blkvsc_req, 0, sizeof(struct blkvsc_request));
        page_buf = alloc_page(GFP_KERNEL);
        if (!page_buf) {
                kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);
                return -ENOMEM;
        }

        init_waitqueue_head(&blkvsc_req->wevent);
        blkvsc_req->dev = blkdev;
        blkvsc_req->req = NULL;
        blkvsc_req->write = 0;

        blkvsc_req->request.DataBuffer.PfnArray[0] = page_to_pfn(page_buf);
        blkvsc_req->request.DataBuffer.Offset = 0;
        blkvsc_req->request.DataBuffer.Length = 12;

        blkvsc_req->cmnd[0] = 0x9E; /* READ_CAPACITY16; */
        blkvsc_req->cmd_len = 16;

        /*
         * Set this here since the completion routine may be invoked
         * and completed before we return
         */
        blkvsc_req->cond = 0;

        blkvsc_submit_request(blkvsc_req, blkvsc_cmd_completion);

        DPRINT_DBG(BLKVSC_DRV, "waiting %p to complete - cond %d\n",
                   blkvsc_req, blkvsc_req->cond);

        wait_event_interruptible(blkvsc_req->wevent, blkvsc_req->cond);

        /* check error */
        if (blkvsc_req->request.Status) {
                scsi_normalize_sense(blkvsc_req->sense_buffer,
                                     SCSI_SENSE_BUFFERSIZE, &sense_hdr);
                if (sense_hdr.asc == 0x3A) {
                        /* Medium not present */
                        blkdev->media_not_present = 1;
                }
                return 0;
        }
        buf = kmap(page_buf);

        /* be to le */
        blkdev->capacity = be64_to_cpu(*(unsigned long long *) &buf[0]) + 1;
        blkdev->sector_size = be32_to_cpu(*(unsigned int *)&buf[8]);

#if 0
        blkdev->capacity = ((buf[0] << 24) | (buf[1] << 16) |
                            (buf[2] << 8) | buf[3]) + 1;
        blkdev->sector_size = (buf[4] << 24) | (buf[5] << 16) |
                              (buf[6] << 8) | buf[7];
#endif

        kunmap(page_buf);

        __free_page(page_buf);

        kmem_cache_free(blkvsc_req->dev->request_pool, blkvsc_req);

        return 0;
}

/**
 * blkvsc_remove() - Callback when our device is removed
 */
static int blkvsc_remove(struct device *device)
{
        struct driver_context *driver_ctx =
                                driver_to_driver_context(device->driver);
        struct blkvsc_driver_context *blkvsc_drv_ctx =
                                (struct blkvsc_driver_context *)driver_ctx;
        struct storvsc_driver_object *storvsc_drv_obj =
                                &blkvsc_drv_ctx->drv_obj;
        struct device_context *device_ctx = device_to_device_context(device);
        struct hv_device *device_obj = &device_ctx->device_obj;
        struct block_device_context *blkdev = dev_get_drvdata(device);
        unsigned long flags;
        int ret;

        DPRINT_ENTER(BLKVSC_DRV);

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_remove()\n");

        if (!storvsc_drv_obj->Base.OnDeviceRemove) {
                DPRINT_EXIT(BLKVSC_DRV);
                return -1;
        }

        /*
         * Call to the vsc driver to let it know that the device is being
         * removed
         */
        ret = storvsc_drv_obj->Base.OnDeviceRemove(device_obj);
        if (ret != 0) {
                /* TODO: */
                DPRINT_ERR(BLKVSC_DRV,
                           "unable to remove blkvsc device (ret %d)", ret);
        }

        /* Get to a known state */
        spin_lock_irqsave(&blkdev->lock, flags);

        blkdev->shutting_down = 1;

        blk_stop_queue(blkdev->gd->queue);

        spin_unlock_irqrestore(&blkdev->lock, flags);

        while (blkdev->num_outstanding_reqs) {
                DPRINT_INFO(STORVSC, "waiting for %d requests to complete...",
                            blkdev->num_outstanding_reqs);
                udelay(100);
        }

        blkvsc_do_flush(blkdev);

        spin_lock_irqsave(&blkdev->lock, flags);

        blkvsc_cancel_pending_reqs(blkdev);

        spin_unlock_irqrestore(&blkdev->lock, flags);

        blk_cleanup_queue(blkdev->gd->queue);

        del_gendisk(blkdev->gd);

        kmem_cache_destroy(blkdev->request_pool);

        kfree(blkdev);

        DPRINT_EXIT(BLKVSC_DRV);

        return ret;
}

static void blkvsc_init_rw(struct blkvsc_request *blkvsc_req)
{
        ASSERT(blkvsc_req->req);
        ASSERT(blkvsc_req->sector_count <= (MAX_MULTIPAGE_BUFFER_COUNT*8));

        blkvsc_req->cmd_len = 16;

        if (blkvsc_req->sector_start > 0xffffffff) {
                if (rq_data_dir(blkvsc_req->req)) {
                        blkvsc_req->write = 1;
                        blkvsc_req->cmnd[0] = WRITE_16;
                } else {
                        blkvsc_req->write = 0;
                        blkvsc_req->cmnd[0] = READ_16;
                }

                blkvsc_req->cmnd[1] |= blk_fua_rq(blkvsc_req->req) ? 0x8 : 0;

                *(unsigned long long *)&blkvsc_req->cmnd[2] =
                                cpu_to_be64(blkvsc_req->sector_start);
                *(unsigned int *)&blkvsc_req->cmnd[10] =
                                cpu_to_be32(blkvsc_req->sector_count);
        } else if ((blkvsc_req->sector_count > 0xff) ||
                   (blkvsc_req->sector_start > 0x1fffff)) {
                if (rq_data_dir(blkvsc_req->req)) {
                        blkvsc_req->write = 1;
                        blkvsc_req->cmnd[0] = WRITE_10;
                } else {
                        blkvsc_req->write = 0;
                        blkvsc_req->cmnd[0] = READ_10;
                }

                blkvsc_req->cmnd[1] |= blk_fua_rq(blkvsc_req->req) ? 0x8 : 0;

                *(unsigned int *)&blkvsc_req->cmnd[2] =
                                cpu_to_be32(blkvsc_req->sector_start);
                *(unsigned short *)&blkvsc_req->cmnd[7] =
                                cpu_to_be16(blkvsc_req->sector_count);
        } else {
                if (rq_data_dir(blkvsc_req->req)) {
                        blkvsc_req->write = 1;
                        blkvsc_req->cmnd[0] = WRITE_6;
                } else {
                        blkvsc_req->write = 0;
                        blkvsc_req->cmnd[0] = READ_6;
                }

                *(unsigned int *)&blkvsc_req->cmnd[1] =
                                cpu_to_be32(blkvsc_req->sector_start) >> 8;
                blkvsc_req->cmnd[1] &= 0x1f;
                blkvsc_req->cmnd[4] = (unsigned char)blkvsc_req->sector_count;
        }
}

static int blkvsc_submit_request(struct blkvsc_request *blkvsc_req,
                        void (*request_completion)(struct hv_storvsc_request *))
{
        struct block_device_context *blkdev = blkvsc_req->dev;
        struct device_context *device_ctx = blkdev->device_ctx;
        struct driver_context *driver_ctx =
                        driver_to_driver_context(device_ctx->device.driver);
        struct blkvsc_driver_context *blkvsc_drv_ctx =
                        (struct blkvsc_driver_context *)driver_ctx;
        struct storvsc_driver_object *storvsc_drv_obj =
                        &blkvsc_drv_ctx->drv_obj;
        struct hv_storvsc_request *storvsc_req;
        int ret;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_submit_request() - "
                   "req %p type %s start_sector %lu count %ld offset %d "
                   "len %d\n", blkvsc_req,
                   (blkvsc_req->write) ? "WRITE" : "READ",
                   (unsigned long) blkvsc_req->sector_start,
                   blkvsc_req->sector_count,
                   blkvsc_req->request.DataBuffer.Offset,
                   blkvsc_req->request.DataBuffer.Length);
#if 0
        for (i = 0; i < (blkvsc_req->request.DataBuffer.Length >> 12); i++) {
                DPRINT_DBG(BLKVSC_DRV, "blkvsc_submit_request() - "
                           "req %p pfn[%d] %llx\n",
                           blkvsc_req, i,
                           blkvsc_req->request.DataBuffer.PfnArray[i]);
        }
#endif

        storvsc_req = &blkvsc_req->request;
        storvsc_req->Extension = (void *)((unsigned long)blkvsc_req +
                                          sizeof(struct blkvsc_request));

        storvsc_req->Type = blkvsc_req->write ? WRITE_TYPE : READ_TYPE;

        storvsc_req->OnIOCompletion = request_completion;
        storvsc_req->Context = blkvsc_req;

        storvsc_req->Host = blkdev->port;
        storvsc_req->Bus = blkdev->path;
        storvsc_req->TargetId = blkdev->target;
        storvsc_req->LunId = 0;  /* this is not really used at all */

        storvsc_req->CdbLen = blkvsc_req->cmd_len;
        storvsc_req->Cdb = blkvsc_req->cmnd;

        storvsc_req->SenseBuffer = blkvsc_req->sense_buffer;
        storvsc_req->SenseBufferSize = SCSI_SENSE_BUFFERSIZE;

        ret = storvsc_drv_obj->OnIORequest(&blkdev->device_ctx->device_obj,
                                           &blkvsc_req->request);
        if (ret == 0)
                blkdev->num_outstanding_reqs++;

        return ret;
}

/*
 * We break the request into 1 or more blkvsc_requests and submit
 * them.  If we cant submit them all, we put them on the
 * pending_list. The blkvsc_request() will work on the pending_list.
 */
static int blkvsc_do_request(struct block_device_context *blkdev,
                             struct request *req)
{
        struct bio *bio = NULL;
        struct bio_vec *bvec = NULL;
        struct bio_vec *prev_bvec = NULL;
        struct blkvsc_request *blkvsc_req = NULL;
        struct blkvsc_request *tmp;
        int databuf_idx = 0;
        int seg_idx = 0;
        sector_t start_sector;
        unsigned long num_sectors = 0;
        int ret = 0;
        int pending = 0;
        struct blkvsc_request_group *group = NULL;

        DPRINT_DBG(BLKVSC_DRV, "blkdev %p req %p sect %lu \n", blkdev, req,
                  (unsigned long)blk_rq_pos(req));

        /* Create a group to tie req to list of blkvsc_reqs */
        group = kmem_cache_alloc(blkdev->request_pool, GFP_ATOMIC);
        if (!group)
                return -ENOMEM;

        INIT_LIST_HEAD(&group->blkvsc_req_list);
        group->outstanding = group->status = 0;

        start_sector = blk_rq_pos(req);

        /* foreach bio in the request */
        if (req->bio) {
                for (bio = req->bio; bio; bio = bio->bi_next) {
                        /*
                         * Map this bio into an existing or new storvsc request
                         */
                        bio_for_each_segment(bvec, bio, seg_idx) {
                                DPRINT_DBG(BLKVSC_DRV, "bio_for_each_segment() "
                                           "- req %p bio %p bvec %p seg_idx %d "
                                           "databuf_idx %d\n", req, bio, bvec,
                                           seg_idx, databuf_idx);

                                /* Get a new storvsc request */
                                /* 1st-time */
                                if ((!blkvsc_req) ||
                                    (databuf_idx >= MAX_MULTIPAGE_BUFFER_COUNT)
                                    /* hole at the begin of page */
                                    || (bvec->bv_offset != 0) ||
                                    /* hold at the end of page */
                                    (prev_bvec &&
                                     (prev_bvec->bv_len != PAGE_SIZE))) {
                                        /* submit the prev one */
                                        if (blkvsc_req) {
                                                blkvsc_req->sector_start = start_sector;
                                                sector_div(blkvsc_req->sector_start, (blkdev->sector_size >> 9));

                                                blkvsc_req->sector_count = num_sectors / (blkdev->sector_size >> 9);
                                                blkvsc_init_rw(blkvsc_req);
                                        }

                                        /*
                                         * Create new blkvsc_req to represent
                                         * the current bvec
                                         */
                                        blkvsc_req = kmem_cache_alloc(blkdev->request_pool, GFP_ATOMIC);
                                        if (!blkvsc_req) {
                                                /* free up everything */
                                                list_for_each_entry_safe(
                                                        blkvsc_req, tmp,
                                                        &group->blkvsc_req_list,
                                                        req_entry) {
                                                        list_del(&blkvsc_req->req_entry);
                                                        kmem_cache_free(blkdev->request_pool, blkvsc_req);
                                                }

                                                kmem_cache_free(blkdev->request_pool, group);
                                                return -ENOMEM;
                                        }

                                        memset(blkvsc_req, 0,
                                               sizeof(struct blkvsc_request));

                                        blkvsc_req->dev = blkdev;
                                        blkvsc_req->req = req;
                                        blkvsc_req->request.DataBuffer.Offset = bvec->bv_offset;
                                        blkvsc_req->request.DataBuffer.Length = 0;

                                        /* Add to the group */
                                        blkvsc_req->group = group;
                                        blkvsc_req->group->outstanding++;
                                        list_add_tail(&blkvsc_req->req_entry,
                                                &blkvsc_req->group->blkvsc_req_list);

                                        start_sector += num_sectors;
                                        num_sectors = 0;
                                        databuf_idx = 0;
                                }

                                /* Add the curr bvec/segment to the curr blkvsc_req */
                                blkvsc_req->request.DataBuffer.PfnArray[databuf_idx] = page_to_pfn(bvec->bv_page);
                                blkvsc_req->request.DataBuffer.Length += bvec->bv_len;

                                prev_bvec = bvec;

                                databuf_idx++;
                                num_sectors += bvec->bv_len >> 9;

                        } /* bio_for_each_segment */

                } /* rq_for_each_bio */
        }

        /* Handle the last one */
        if (blkvsc_req) {
                DPRINT_DBG(BLKVSC_DRV, "blkdev %p req %p group %p count %d\n",
                           blkdev, req, blkvsc_req->group,
                           blkvsc_req->group->outstanding);

                blkvsc_req->sector_start = start_sector;
                sector_div(blkvsc_req->sector_start,
                           (blkdev->sector_size >> 9));

                blkvsc_req->sector_count = num_sectors /
                                           (blkdev->sector_size >> 9);

                blkvsc_init_rw(blkvsc_req);
        }

        list_for_each_entry(blkvsc_req, &group->blkvsc_req_list, req_entry) {
                if (pending) {
                        DPRINT_DBG(BLKVSC_DRV, "adding blkvsc_req to "
                                   "pending_list - blkvsc_req %p start_sect %lu"
                                   " sect_count %ld (%lu %ld)\n", blkvsc_req,
                                   (unsigned long)blkvsc_req->sector_start,
                                   blkvsc_req->sector_count,
                                   (unsigned long)start_sector,
                                   (unsigned long)num_sectors);

                        list_add_tail(&blkvsc_req->pend_entry,
                                      &blkdev->pending_list);
                } else {
                        ret = blkvsc_submit_request(blkvsc_req,
                                                    blkvsc_request_completion);
                        if (ret == -1) {
                                pending = 1;
                                list_add_tail(&blkvsc_req->pend_entry,
                                              &blkdev->pending_list);
                        }

                        DPRINT_DBG(BLKVSC_DRV, "submitted blkvsc_req %p "
                                   "start_sect %lu sect_count %ld (%lu %ld) "
                                   "ret %d\n", blkvsc_req,
                                   (unsigned long)blkvsc_req->sector_start,
                                   blkvsc_req->sector_count,
                                   (unsigned long)start_sector,
                                   num_sectors, ret);
                }
        }

        return pending;
}

static void blkvsc_cmd_completion(struct hv_storvsc_request *request)
{
        struct blkvsc_request *blkvsc_req =
                        (struct blkvsc_request *)request->Context;
        struct block_device_context *blkdev =
                        (struct block_device_context *)blkvsc_req->dev;
        struct scsi_sense_hdr sense_hdr;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_cmd_completion() - req %p\n",
                   blkvsc_req);

        blkdev->num_outstanding_reqs--;

        if (blkvsc_req->request.Status)
                if (scsi_normalize_sense(blkvsc_req->sense_buffer,
                                         SCSI_SENSE_BUFFERSIZE, &sense_hdr))
                        scsi_print_sense_hdr("blkvsc", &sense_hdr);

        blkvsc_req->cond = 1;
        wake_up_interruptible(&blkvsc_req->wevent);
}

static void blkvsc_request_completion(struct hv_storvsc_request *request)
{
        struct blkvsc_request *blkvsc_req =
                        (struct blkvsc_request *)request->Context;
        struct block_device_context *blkdev =
                        (struct block_device_context *)blkvsc_req->dev;
        unsigned long flags;
        struct blkvsc_request *comp_req, *tmp;

        ASSERT(blkvsc_req->group);

        DPRINT_DBG(BLKVSC_DRV, "blkdev %p blkvsc_req %p group %p type %s "
                   "sect_start %lu sect_count %ld len %d group outstd %d "
                   "total outstd %d\n",
                   blkdev, blkvsc_req, blkvsc_req->group,
                   (blkvsc_req->write) ? "WRITE" : "READ",
                   (unsigned long)blkvsc_req->sector_start,
                   blkvsc_req->sector_count,
                   blkvsc_req->request.DataBuffer.Length,
                   blkvsc_req->group->outstanding,
                   blkdev->num_outstanding_reqs);

        spin_lock_irqsave(&blkdev->lock, flags);

        blkdev->num_outstanding_reqs--;
        blkvsc_req->group->outstanding--;

        /*
         * Only start processing when all the blkvsc_reqs are
         * completed. This guarantees no out-of-order blkvsc_req
         * completion when calling end_that_request_first()
         */
        if (blkvsc_req->group->outstanding == 0) {
                list_for_each_entry_safe(comp_req, tmp,
                                         &blkvsc_req->group->blkvsc_req_list,
                                         req_entry) {
                        DPRINT_DBG(BLKVSC_DRV, "completing blkvsc_req %p "
                                   "sect_start %lu sect_count %ld \n",
                                   comp_req,
                                   (unsigned long)comp_req->sector_start,
                                   comp_req->sector_count);

                        list_del(&comp_req->req_entry);

                        if (!__blk_end_request(comp_req->req,
                                (!comp_req->request.Status ? 0 : -EIO),
                                comp_req->sector_count * blkdev->sector_size)) {
                                /*
                                 * All the sectors have been xferred ie the
                                 * request is done
                                 */
                                DPRINT_DBG(BLKVSC_DRV, "req %p COMPLETED\n",
                                           comp_req->req);
                                kmem_cache_free(blkdev->request_pool,
                                                comp_req->group);
                        }

                        kmem_cache_free(blkdev->request_pool, comp_req);
                }

                if (!blkdev->shutting_down) {
                        blkvsc_do_pending_reqs(blkdev);
                        blk_start_queue(blkdev->gd->queue);
                        blkvsc_request(blkdev->gd->queue);
                }
        }

        spin_unlock_irqrestore(&blkdev->lock, flags);
}

static int blkvsc_cancel_pending_reqs(struct block_device_context *blkdev)
{
        struct blkvsc_request *pend_req, *tmp;
        struct blkvsc_request *comp_req, *tmp2;

        int ret = 0;

        DPRINT_DBG(BLKVSC_DRV, "blkvsc_cancel_pending_reqs()");

        /* Flush the pending list first */
        list_for_each_entry_safe(pend_req, tmp, &blkdev->pending_list,
                                 pend_entry) {
                /*
                 * The pend_req could be part of a partially completed
                 * request. If so, complete those req first until we
                 * hit the pend_req
                 */
                list_for_each_entry_safe(comp_req, tmp2,
                                         &pend_req->group->blkvsc_req_list,
                                         req_entry) {
                        DPRINT_DBG(BLKVSC_DRV, "completing blkvsc_req %p "
                                   "sect_start %lu sect_count %ld \n",
                                   comp_req,
                                   (unsigned long) comp_req->sector_start,
                                   comp_req->sector_count);

                        if (comp_req == pend_req)
                                break;

                        list_del(&comp_req->req_entry);

                        if (comp_req->req) {
                                ret = __blk_end_request(comp_req->req,
                                        (!comp_req->request.Status ? 0 : -EIO),
                                        comp_req->sector_count *
                                        blkdev->sector_size);
                                ASSERT(ret != 0);
                        }

                        kmem_cache_free(blkdev->request_pool, comp_req);
                }

                DPRINT_DBG(BLKVSC_DRV, "cancelling pending request - %p\n",
                           pend_req);

                list_del(&pend_req->pend_entry);

                list_del(&pend_req->req_entry);

                if (comp_req->req) {
                        if (!__blk_end_request(pend_req->req, -EIO,
                                               pend_req->sector_count *
                                               blkdev->sector_size)) {
                                /*
                                 * All the sectors have been xferred ie the
                                 * request is done
                                 */
                                DPRINT_DBG(BLKVSC_DRV,
                                           "blkvsc_cancel_pending_reqs() - "
                                           "req %p COMPLETED\n", pend_req->req);
                                kmem_cache_free(blkdev->request_pool,
                                                pend_req->group);
                        }
                }

                kmem_cache_free(blkdev->request_pool, pend_req);
        }

        return ret;
}

static int blkvsc_do_pending_reqs(struct block_device_context *blkdev)
{
        struct blkvsc_request *pend_req, *tmp;
        int ret = 0;

        /* Flush the pending list first */
        list_for_each_entry_safe(pend_req, tmp, &blkdev->pending_list,
                                 pend_entry) {
                DPRINT_DBG(BLKVSC_DRV, "working off pending_list - %p\n",
                           pend_req);

                ret = blkvsc_submit_request(pend_req,
                                            blkvsc_request_completion);
                if (ret != 0)
                        break;
                else
                        list_del(&pend_req->pend_entry);
        }

        return ret;
}

static void blkvsc_request(struct request_queue *queue)
{
        struct block_device_context *blkdev = NULL;
        struct request *req;
        int ret = 0;

        DPRINT_DBG(BLKVSC_DRV, "- enter \n");
        while ((req = blk_peek_request(queue)) != NULL) {
                DPRINT_DBG(BLKVSC_DRV, "- req %p\n", req);

                blkdev = req->rq_disk->private_data;
                if (blkdev->shutting_down || !blk_fs_request(req) ||
                    blkdev->media_not_present) {
                        __blk_end_request_cur(req, 0);
                        continue;
                }

                ret = blkvsc_do_pending_reqs(blkdev);

                if (ret != 0) {
                        DPRINT_DBG(BLKVSC_DRV,
                                   "- stop queue - pending_list not empty\n");
                        blk_stop_queue(queue);
                        break;
                }

                blk_start_request(req);

                ret = blkvsc_do_request(blkdev, req);
                if (ret > 0) {
                        DPRINT_DBG(BLKVSC_DRV, "- stop queue - no room\n");
                        blk_stop_queue(queue);
                        break;
                } else if (ret < 0) {
                        DPRINT_DBG(BLKVSC_DRV, "- stop queue - no mem\n");
                        blk_requeue_request(queue, req);
                        blk_stop_queue(queue);
                        break;
                }
        }
}

static int blkvsc_open(struct block_device *bdev, fmode_t mode)
{
        struct block_device_context *blkdev = bdev->bd_disk->private_data;

        DPRINT_DBG(BLKVSC_DRV, "- users %d disk %s\n", blkdev->users,
                   blkdev->gd->disk_name);

        spin_lock(&blkdev->lock);

        if (!blkdev->users && blkdev->device_type == DVD_TYPE) {
                spin_unlock(&blkdev->lock);
                check_disk_change(bdev);
                spin_lock(&blkdev->lock);
        }

        blkdev->users++;

        spin_unlock(&blkdev->lock);
        return 0;
}

static int blkvsc_release(struct gendisk *disk, fmode_t mode)
{
        struct block_device_context *blkdev = disk->private_data;

        DPRINT_DBG(BLKVSC_DRV, "- users %d disk %s\n", blkdev->users,
                   blkdev->gd->disk_name);

        spin_lock(&blkdev->lock);
        if (blkdev->users == 1) {
                spin_unlock(&blkdev->lock);
                blkvsc_do_flush(blkdev);
                spin_lock(&blkdev->lock);
        }

        blkdev->users--;

        spin_unlock(&blkdev->lock);
        return 0;
}

static int blkvsc_media_changed(struct gendisk *gd)
{
        DPRINT_DBG(BLKVSC_DRV, "- enter\n");
        return 1;
}

static int blkvsc_revalidate_disk(struct gendisk *gd)
{
        struct block_device_context *blkdev = gd->private_data;

        DPRINT_DBG(BLKVSC_DRV, "- enter\n");

        if (blkdev->device_type == DVD_TYPE) {
                blkvsc_do_read_capacity(blkdev);
                set_capacity(blkdev->gd, blkdev->capacity *
                            (blkdev->sector_size/512));
                blk_queue_logical_block_size(gd->queue, blkdev->sector_size);
        }
        return 0;
}

static int blkvsc_getgeo(struct block_device *bd, struct hd_geometry *hg)
{
        sector_t total_sectors = get_capacity(bd->bd_disk);
        sector_t cylinder_times_heads = 0;
        sector_t temp = 0;

        int sectors_per_track = 0;
        int heads = 0;
        int cylinders = 0;
        int rem = 0;

        if (total_sectors > (65535 * 16 * 255))
                total_sectors = (65535 * 16 * 255);

        if (total_sectors >= (65535 * 16 * 63)) {
                sectors_per_track = 255;
                heads = 16;

                cylinder_times_heads = total_sectors;
                /* sector_div stores the quotient in cylinder_times_heads */
                rem = sector_div(cylinder_times_heads, sectors_per_track);
        } else {
                sectors_per_track = 17;

                cylinder_times_heads = total_sectors;
                /* sector_div stores the quotient in cylinder_times_heads */
                rem = sector_div(cylinder_times_heads, sectors_per_track);

                temp = cylinder_times_heads + 1023;
                /* sector_div stores the quotient in temp */
                rem = sector_div(temp, 1024);

                heads = temp;

                if (heads < 4)
                        heads = 4;


                if (cylinder_times_heads >= (heads * 1024) || (heads > 16)) {
                        sectors_per_track = 31;
                        heads = 16;

                        cylinder_times_heads = total_sectors;
                        /*
                         * sector_div stores the quotient in
                         * cylinder_times_heads
                         */
                        rem = sector_div(cylinder_times_heads,
                                         sectors_per_track);
                }

                if (cylinder_times_heads >= (heads * 1024)) {
                        sectors_per_track = 63;
                        heads = 16;

                        cylinder_times_heads = total_sectors;
                        /*
                         * sector_div stores the quotient in
                         * cylinder_times_heads
                         */
                        rem = sector_div(cylinder_times_heads,
                                         sectors_per_track);
                }
        }

        temp = cylinder_times_heads;
        /* sector_div stores the quotient in temp */
        rem = sector_div(temp, heads);
        cylinders = temp;

        hg->heads = heads;
        hg->sectors = sectors_per_track;
        hg->cylinders = cylinders;

        DPRINT_INFO(BLKVSC_DRV, "CHS (%d, %d, %d)", cylinders, heads,
                    sectors_per_track);

    return 0;
}

static int blkvsc_ioctl(struct block_device *bd, fmode_t mode,
                        unsigned cmd, unsigned long argument)
{
/*      struct block_device_context *blkdev = bd->bd_disk->private_data; */
        int ret;

        switch (cmd) {
        /*
         * TODO: I think there is certain format for HDIO_GET_IDENTITY rather
         * than just a GUID. Commented it out for now.
         */
#if 0
        case HDIO_GET_IDENTITY:
                DPRINT_INFO(BLKVSC_DRV, "HDIO_GET_IDENTITY\n");
                if (copy_to_user((void __user *)arg, blkdev->device_id,
                                 blkdev->device_id_len))
                        ret = -EFAULT;
                break;
#endif
        default:
                ret = -EINVAL;
                break;
        }

        return ret;
}

static int __init blkvsc_init(void)
{
        int ret;

        ASSERT(sizeof(sector_t) == 8); /* Make sure CONFIG_LBD is set */

        DPRINT_ENTER(BLKVSC_DRV);

        DPRINT_INFO(BLKVSC_DRV, "Blkvsc initializing....");

        ret = blkvsc_drv_init(BlkVscInitialize);

        DPRINT_EXIT(BLKVSC_DRV);

        return ret;
}

static void __exit blkvsc_exit(void)
{
        DPRINT_ENTER(BLKVSC_DRV);
        blkvsc_drv_exit();
        DPRINT_ENTER(BLKVSC_DRV);
}

MODULE_LICENSE("GPL");
module_param(blkvsc_ringbuffer_size, int, S_IRUGO);
module_init(blkvsc_init);
module_exit(blkvsc_exit);