Merge tag 'v3.10.55' into update

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / scsi / storvsc_drv.c

/*
 * 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>
 *   K. Y. Srinivasan <kys@microsoft.com>
 */

#include <linux/kernel.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/hyperv.h>
#include <linux/mempool.h>
#include <linux/blkdev.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_dbg.h>

/*
 * All wire protocol details (storage protocol between the guest and the host)
 * are consolidated here.
 *
 * Begin protocol definitions.
 */

/*
 * Version history:
 * V1 Beta: 0.1
 * V1 RC < 2008/1/31: 1.0
 * V1 RC > 2008/1/31:  2.0
 * Win7: 4.2
 */

#define VMSTOR_CURRENT_MAJOR  4
#define VMSTOR_CURRENT_MINOR  2


/*  Packet structure describing virtual storage requests. */
enum vstor_packet_operation {
        VSTOR_OPERATION_COMPLETE_IO             = 1,
        VSTOR_OPERATION_REMOVE_DEVICE           = 2,
        VSTOR_OPERATION_EXECUTE_SRB             = 3,
        VSTOR_OPERATION_RESET_LUN               = 4,
        VSTOR_OPERATION_RESET_ADAPTER           = 5,
        VSTOR_OPERATION_RESET_BUS               = 6,
        VSTOR_OPERATION_BEGIN_INITIALIZATION    = 7,
        VSTOR_OPERATION_END_INITIALIZATION      = 8,
        VSTOR_OPERATION_QUERY_PROTOCOL_VERSION  = 9,
        VSTOR_OPERATION_QUERY_PROPERTIES        = 10,
        VSTOR_OPERATION_ENUMERATE_BUS           = 11,
        VSTOR_OPERATION_MAXIMUM                 = 11
};

/*
 * Platform neutral description of a scsi request -
 * this remains the same across the write regardless of 32/64 bit
 * note: it's patterned off the SCSI_PASS_THROUGH structure
 */
#define STORVSC_MAX_CMD_LEN                     0x10
#define STORVSC_SENSE_BUFFER_SIZE               0x12
#define STORVSC_MAX_BUF_LEN_WITH_PADDING        0x14

struct vmscsi_request {
        u16 length;
        u8 srb_status;
        u8 scsi_status;

        u8  port_number;
        u8  path_id;
        u8  target_id;
        u8  lun;

        u8  cdb_length;
        u8  sense_info_length;
        u8  data_in;
        u8  reserved;

        u32 data_transfer_length;

        union {
                u8 cdb[STORVSC_MAX_CMD_LEN];
                u8 sense_data[STORVSC_SENSE_BUFFER_SIZE];
                u8 reserved_array[STORVSC_MAX_BUF_LEN_WITH_PADDING];
        };
} __attribute((packed));


/*
 * This structure is sent during the intialization phase to get the different
 * properties of the channel.
 */
struct vmstorage_channel_properties {
        u16 protocol_version;
        u8  path_id;
        u8 target_id;

        /* Note: port number is only really known on the client side */
        u32  port_number;
        u32  flags;
        u32   max_transfer_bytes;

        /*
         * This id is unique for each channel and will correspond with
         * vendor specific data in the inquiry data.
         */

        u64  unique_id;
} __packed;

/*  This structure is sent during the storage protocol negotiations. */
struct vmstorage_protocol_version {
        /* Major (MSW) and minor (LSW) version numbers. */
        u16 major_minor;

        /*
         * Revision number is auto-incremented whenever this file is changed
         * (See FILL_VMSTOR_REVISION macro above).  Mismatch does not
         * definitely indicate incompatibility--but it does indicate mismatched
         * builds.
         * This is only used on the windows side. Just set it to 0.
         */
        u16 revision;
} __packed;

/* Channel Property Flags */
#define STORAGE_CHANNEL_REMOVABLE_FLAG          0x1
#define STORAGE_CHANNEL_EMULATED_IDE_FLAG       0x2

struct vstor_packet {
        /* Requested operation type */
        enum vstor_packet_operation operation;

        /*  Flags - see below for values */
        u32 flags;

        /* Status of the request returned from the server side. */
        u32 status;

        /* Data payload area */
        union {
                /*
                 * Structure used to forward SCSI commands from the
                 * client to the server.
                 */
                struct vmscsi_request vm_srb;

                /* Structure used to query channel properties. */
                struct vmstorage_channel_properties storage_channel_properties;

                /* Used during version negotiations. */
                struct vmstorage_protocol_version version;
        };
} __packed;

/*
 * Packet Flags:
 *
 * This flag indicates that the server should send back a completion for this
 * packet.
 */

#define REQUEST_COMPLETION_FLAG 0x1

/* Matches Windows-end */
enum storvsc_request_type {
        WRITE_TYPE = 0,
        READ_TYPE,
        UNKNOWN_TYPE,
};

/*
 * SRB status codes and masks; a subset of the codes used here.
 */

#define SRB_STATUS_AUTOSENSE_VALID      0x80
#define SRB_STATUS_INVALID_LUN  0x20
#define SRB_STATUS_SUCCESS      0x01
#define SRB_STATUS_ABORTED      0x02
#define SRB_STATUS_ERROR        0x04

/*
 * This is the end of Protocol specific defines.
 */


/*
 * We setup a mempool to allocate request structures for this driver
 * on a per-lun basis. The following define specifies the number of
 * elements in the pool.
 */

#define STORVSC_MIN_BUF_NR                              64
static int storvsc_ringbuffer_size = (20 * PAGE_SIZE);

module_param(storvsc_ringbuffer_size, int, S_IRUGO);
MODULE_PARM_DESC(storvsc_ringbuffer_size, "Ring buffer size (bytes)");

#define STORVSC_MAX_IO_REQUESTS                         128

/*
 * In Hyper-V, each port/path/target maps to 1 scsi host adapter.  In
 * reality, the path/target is not used (ie always set to 0) so our
 * scsi host adapter essentially has 1 bus with 1 target that contains
 * up to 256 luns.
 */
#define STORVSC_MAX_LUNS_PER_TARGET                     64
#define STORVSC_MAX_TARGETS                             1
#define STORVSC_MAX_CHANNELS                            1



struct storvsc_cmd_request {
        struct list_head entry;
        struct scsi_cmnd *cmd;

        unsigned int bounce_sgl_count;
        struct scatterlist *bounce_sgl;

        struct hv_device *device;

        /* Synchronize the request/response if needed */
        struct completion wait_event;

        unsigned char *sense_buffer;
        struct hv_multipage_buffer data_buffer;
        struct vstor_packet vstor_packet;
};


/* A storvsc device is a device object that contains a vmbus channel */
struct storvsc_device {
        struct hv_device *device;

        bool     destroy;
        bool     drain_notify;
        atomic_t num_outstanding_req;
        struct Scsi_Host *host;

        wait_queue_head_t waiting_to_drain;

        /*
         * Each unique Port/Path/Target represents 1 channel ie scsi
         * controller. In reality, the pathid, targetid is always 0
         * and the port is set by us
         */
        unsigned int port_number;
        unsigned char path_id;
        unsigned char target_id;

        /* Used for vsc/vsp channel reset process */
        struct storvsc_cmd_request init_request;
        struct storvsc_cmd_request reset_request;
};

struct stor_mem_pools {
        struct kmem_cache *request_pool;
        mempool_t *request_mempool;
};

struct hv_host_device {
        struct hv_device *dev;
        unsigned int port;
        unsigned char path;
        unsigned char target;
};

struct storvsc_scan_work {
        struct work_struct work;
        struct Scsi_Host *host;
        uint lun;
};

static void storvsc_device_scan(struct work_struct *work)
{
        struct storvsc_scan_work *wrk;
        uint lun;
        struct scsi_device *sdev;

        wrk = container_of(work, struct storvsc_scan_work, work);
        lun = wrk->lun;

        sdev = scsi_device_lookup(wrk->host, 0, 0, lun);
        if (!sdev)
                goto done;
        scsi_rescan_device(&sdev->sdev_gendev);
        scsi_device_put(sdev);

done:
        kfree(wrk);
}

static void storvsc_bus_scan(struct work_struct *work)
{
        struct storvsc_scan_work *wrk;
        int id, order_id;

        wrk = container_of(work, struct storvsc_scan_work, work);
        for (id = 0; id < wrk->host->max_id; ++id) {
                if (wrk->host->reverse_ordering)
                        order_id = wrk->host->max_id - id - 1;
                else
                        order_id = id;

                scsi_scan_target(&wrk->host->shost_gendev, 0,
                                order_id, SCAN_WILD_CARD, 1);
        }
        kfree(wrk);
}

static void storvsc_remove_lun(struct work_struct *work)
{
        struct storvsc_scan_work *wrk;
        struct scsi_device *sdev;

        wrk = container_of(work, struct storvsc_scan_work, work);
        if (!scsi_host_get(wrk->host))
                goto done;

        sdev = scsi_device_lookup(wrk->host, 0, 0, wrk->lun);

        if (sdev) {
                scsi_remove_device(sdev);
                scsi_device_put(sdev);
        }
        scsi_host_put(wrk->host);

done:
        kfree(wrk);
}

/*
 * Major/minor macros.  Minor version is in LSB, meaning that earlier flat
 * version numbers will be interpreted as "0.x" (i.e., 1 becomes 0.1).
 */

static inline u16 storvsc_get_version(u8 major, u8 minor)
{
        u16 version;

        version = ((major << 8) | minor);
        return version;
}

/*
 * We can get incoming messages from the host that are not in response to
 * messages that we have sent out. An example of this would be messages
 * received by the guest to notify dynamic addition/removal of LUNs. To
 * deal with potential race conditions where the driver may be in the
 * midst of being unloaded when we might receive an unsolicited message
 * from the host, we have implemented a mechanism to gurantee sequential
 * consistency:
 *
 * 1) Once the device is marked as being destroyed, we will fail all
 *    outgoing messages.
 * 2) We permit incoming messages when the device is being destroyed,
 *    only to properly account for messages already sent out.
 */

static inline struct storvsc_device *get_out_stor_device(
                                        struct hv_device *device)
{
        struct storvsc_device *stor_device;

        stor_device = hv_get_drvdata(device);

        if (stor_device && stor_device->destroy)
                stor_device = NULL;

        return stor_device;
}


static inline void storvsc_wait_to_drain(struct storvsc_device *dev)
{
        dev->drain_notify = true;
        wait_event(dev->waiting_to_drain,
                   atomic_read(&dev->num_outstanding_req) == 0);
        dev->drain_notify = false;
}

static inline struct storvsc_device *get_in_stor_device(
                                        struct hv_device *device)
{
        struct storvsc_device *stor_device;

        stor_device = hv_get_drvdata(device);

        if (!stor_device)
                goto get_in_err;

        /*
         * If the device is being destroyed; allow incoming
         * traffic only to cleanup outstanding requests.
         */

        if (stor_device->destroy  &&
                (atomic_read(&stor_device->num_outstanding_req) == 0))
                stor_device = NULL;

get_in_err:
        return stor_device;

}

static void destroy_bounce_buffer(struct scatterlist *sgl,
                                  unsigned int sg_count)
{
        int i;
        struct page *page_buf;

        for (i = 0; i < sg_count; i++) {
                page_buf = sg_page((&sgl[i]));
                if (page_buf != NULL)
                        __free_page(page_buf);
        }

        kfree(sgl);
}

static int do_bounce_buffer(struct scatterlist *sgl, unsigned int sg_count)
{
        int i;

        /* No need to check */
        if (sg_count < 2)
                return -1;

        /* We have at least 2 sg entries */
        for (i = 0; i < sg_count; i++) {
                if (i == 0) {
                        /* make sure 1st one does not have hole */
                        if (sgl[i].offset + sgl[i].length != PAGE_SIZE)
                                return i;
                } else if (i == sg_count - 1) {
                        /* make sure last one does not have hole */
                        if (sgl[i].offset != 0)
                                return i;
                } else {
                        /* make sure no hole in the middle */
                        if (sgl[i].length != PAGE_SIZE || sgl[i].offset != 0)
                                return i;
                }
        }
        return -1;
}

static struct scatterlist *create_bounce_buffer(struct scatterlist *sgl,
                                                unsigned int sg_count,
                                                unsigned int len,
                                                int write)
{
        int i;
        int num_pages;
        struct scatterlist *bounce_sgl;
        struct page *page_buf;
        unsigned int buf_len = ((write == WRITE_TYPE) ? 0 : PAGE_SIZE);

        num_pages = ALIGN(len, PAGE_SIZE) >> PAGE_SHIFT;

        bounce_sgl = kcalloc(num_pages, sizeof(struct scatterlist), GFP_ATOMIC);
        if (!bounce_sgl)
                return NULL;

        sg_init_table(bounce_sgl, num_pages);
        for (i = 0; i < num_pages; i++) {
                page_buf = alloc_page(GFP_ATOMIC);
                if (!page_buf)
                        goto cleanup;
                sg_set_page(&bounce_sgl[i], page_buf, buf_len, 0);
        }

        return bounce_sgl;

cleanup:
        destroy_bounce_buffer(bounce_sgl, num_pages);
        return NULL;
}

/* Disgusting wrapper functions */
static inline unsigned long sg_kmap_atomic(struct scatterlist *sgl, int idx)
{
        void *addr = kmap_atomic(sg_page(sgl + idx));
        return (unsigned long)addr;
}

static inline void sg_kunmap_atomic(unsigned long addr)
{
        kunmap_atomic((void *)addr);
}


/* Assume the original sgl has enough room */
static unsigned int copy_from_bounce_buffer(struct scatterlist *orig_sgl,
                                            struct scatterlist *bounce_sgl,
                                            unsigned int orig_sgl_count,
                                            unsigned int bounce_sgl_count)
{
        int i;
        int j = 0;
        unsigned long src, dest;
        unsigned int srclen, destlen, copylen;
        unsigned int total_copied = 0;
        unsigned long bounce_addr = 0;
        unsigned long dest_addr = 0;
        unsigned long flags;

        local_irq_save(flags);

        for (i = 0; i < orig_sgl_count; i++) {
                dest_addr = sg_kmap_atomic(orig_sgl,i) + orig_sgl[i].offset;
                dest = dest_addr;
                destlen = orig_sgl[i].length;

                if (bounce_addr == 0)
                        bounce_addr = sg_kmap_atomic(bounce_sgl,j);

                while (destlen) {
                        src = bounce_addr + bounce_sgl[j].offset;
                        srclen = bounce_sgl[j].length - bounce_sgl[j].offset;

                        copylen = min(srclen, destlen);
                        memcpy((void *)dest, (void *)src, copylen);

                        total_copied += copylen;
                        bounce_sgl[j].offset += copylen;
                        destlen -= copylen;
                        dest += copylen;

                        if (bounce_sgl[j].offset == bounce_sgl[j].length) {
                                /* full */
                                sg_kunmap_atomic(bounce_addr);
                                j++;

                                /*
                                 * It is possible that the number of elements
                                 * in the bounce buffer may not be equal to
                                 * the number of elements in the original
                                 * scatter list. Handle this correctly.
                                 */

                                if (j == bounce_sgl_count) {
                                        /*
                                         * We are done; cleanup and return.
                                         */
                                        sg_kunmap_atomic(dest_addr - orig_sgl[i].offset);
                                        local_irq_restore(flags);
                                        return total_copied;
                                }

                                /* if we need to use another bounce buffer */
                                if (destlen || i != orig_sgl_count - 1)
                                        bounce_addr = sg_kmap_atomic(bounce_sgl,j);
                        } else if (destlen == 0 && i == orig_sgl_count - 1) {
                                /* unmap the last bounce that is < PAGE_SIZE */
                                sg_kunmap_atomic(bounce_addr);
                        }
                }

                sg_kunmap_atomic(dest_addr - orig_sgl[i].offset);
        }

        local_irq_restore(flags);

        return total_copied;
}

/* Assume the bounce_sgl has enough room ie using the create_bounce_buffer() */
static unsigned int copy_to_bounce_buffer(struct scatterlist *orig_sgl,
                                          struct scatterlist *bounce_sgl,
                                          unsigned int orig_sgl_count)
{
        int i;
        int j = 0;
        unsigned long src, dest;
        unsigned int srclen, destlen, copylen;
        unsigned int total_copied = 0;
        unsigned long bounce_addr = 0;
        unsigned long src_addr = 0;
        unsigned long flags;

        local_irq_save(flags);

        for (i = 0; i < orig_sgl_count; i++) {
                src_addr = sg_kmap_atomic(orig_sgl,i) + orig_sgl[i].offset;
                src = src_addr;
                srclen = orig_sgl[i].length;

                if (bounce_addr == 0)
                        bounce_addr = sg_kmap_atomic(bounce_sgl,j);

                while (srclen) {
                        /* assume bounce offset always == 0 */
                        dest = bounce_addr + bounce_sgl[j].length;
                        destlen = PAGE_SIZE - bounce_sgl[j].length;

                        copylen = min(srclen, destlen);
                        memcpy((void *)dest, (void *)src, copylen);

                        total_copied += copylen;
                        bounce_sgl[j].length += copylen;
                        srclen -= copylen;
                        src += copylen;

                        if (bounce_sgl[j].length == PAGE_SIZE) {
                                /* full..move to next entry */
                                sg_kunmap_atomic(bounce_addr);
                                j++;

                                /* if we need to use another bounce buffer */
                                if (srclen || i != orig_sgl_count - 1)
                                        bounce_addr = sg_kmap_atomic(bounce_sgl,j);

                        } else if (srclen == 0 && i == orig_sgl_count - 1) {
                                /* unmap the last bounce that is < PAGE_SIZE */
                                sg_kunmap_atomic(bounce_addr);
                        }
                }

                sg_kunmap_atomic(src_addr - orig_sgl[i].offset);
        }

        local_irq_restore(flags);

        return total_copied;
}

static int storvsc_channel_init(struct hv_device *device)
{
        struct storvsc_device *stor_device;
        struct storvsc_cmd_request *request;
        struct vstor_packet *vstor_packet;
        int ret, t;

        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return -ENODEV;

        request = &stor_device->init_request;
        vstor_packet = &request->vstor_packet;

        /*
         * Now, initiate the vsc/vsp initialization protocol on the open
         * channel
         */
        memset(request, 0, sizeof(struct storvsc_cmd_request));
        init_completion(&request->wait_event);
        vstor_packet->operation = VSTOR_OPERATION_BEGIN_INITIALIZATION;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               sizeof(struct vstor_packet),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0)
                goto cleanup;


        /* reuse the packet for version range supported */
        memset(vstor_packet, 0, sizeof(struct vstor_packet));
        vstor_packet->operation = VSTOR_OPERATION_QUERY_PROTOCOL_VERSION;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;

        vstor_packet->version.major_minor =
                storvsc_get_version(VMSTOR_CURRENT_MAJOR, VMSTOR_CURRENT_MINOR);

        /*
         * The revision number is only used in Windows; set it to 0.
         */
        vstor_packet->version.revision = 0;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               sizeof(struct vstor_packet),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0)
                goto cleanup;


        memset(vstor_packet, 0, sizeof(struct vstor_packet));
        vstor_packet->operation = VSTOR_OPERATION_QUERY_PROPERTIES;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;
        vstor_packet->storage_channel_properties.port_number =
                                        stor_device->port_number;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               sizeof(struct vstor_packet),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0)
                goto cleanup;

        stor_device->path_id = vstor_packet->storage_channel_properties.path_id;
        stor_device->target_id
                = vstor_packet->storage_channel_properties.target_id;

        memset(vstor_packet, 0, sizeof(struct vstor_packet));
        vstor_packet->operation = VSTOR_OPERATION_END_INITIALIZATION;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               sizeof(struct vstor_packet),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);

        if (ret != 0)
                goto cleanup;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0) {
                ret = -ETIMEDOUT;
                goto cleanup;
        }

        if (vstor_packet->operation != VSTOR_OPERATION_COMPLETE_IO ||
            vstor_packet->status != 0)
                goto cleanup;


cleanup:
        return ret;
}

static void storvsc_handle_error(struct vmscsi_request *vm_srb,
                                struct scsi_cmnd *scmnd,
                                struct Scsi_Host *host,
                                u8 asc, u8 ascq)
{
        struct storvsc_scan_work *wrk;
        void (*process_err_fn)(struct work_struct *work);
        bool do_work = false;

        switch (vm_srb->srb_status) {
        case SRB_STATUS_ERROR:
                /*
                 * If there is an error; offline the device since all
                 * error recovery strategies would have already been
                 * deployed on the host side. However, if the command
                 * were a pass-through command deal with it appropriately.
                 */
                switch (scmnd->cmnd[0]) {
                case ATA_16:
                case ATA_12:
                        set_host_byte(scmnd, DID_PASSTHROUGH);
                        break;
                /*
                 * On Some Windows hosts TEST_UNIT_READY command can return
                 * SRB_STATUS_ERROR, let the upper level code deal with it
                 * based on the sense information.
                 */
                case TEST_UNIT_READY:
                        break;
                default:
                        set_host_byte(scmnd, DID_TARGET_FAILURE);
                }
                break;
        case SRB_STATUS_INVALID_LUN:
                do_work = true;
                process_err_fn = storvsc_remove_lun;
                break;
        case (SRB_STATUS_ABORTED | SRB_STATUS_AUTOSENSE_VALID):
                if ((asc == 0x2a) && (ascq == 0x9)) {
                        do_work = true;
                        process_err_fn = storvsc_device_scan;
                        /*
                         * Retry the I/O that trigerred this.
                         */
                        set_host_byte(scmnd, DID_REQUEUE);
                }
                break;
        }

        if (!do_work)
                return;

        /*
         * We need to schedule work to process this error; schedule it.
         */
        wrk = kmalloc(sizeof(struct storvsc_scan_work), GFP_ATOMIC);
        if (!wrk) {
                set_host_byte(scmnd, DID_TARGET_FAILURE);
                return;
        }

        wrk->host = host;
        wrk->lun = vm_srb->lun;
        INIT_WORK(&wrk->work, process_err_fn);
        schedule_work(&wrk->work);
}


static void storvsc_command_completion(struct storvsc_cmd_request *cmd_request)
{
        struct scsi_cmnd *scmnd = cmd_request->cmd;
        struct hv_host_device *host_dev = shost_priv(scmnd->device->host);
        void (*scsi_done_fn)(struct scsi_cmnd *);
        struct scsi_sense_hdr sense_hdr;
        struct vmscsi_request *vm_srb;
        struct stor_mem_pools *memp = scmnd->device->hostdata;
        struct Scsi_Host *host;
        struct storvsc_device *stor_dev;
        struct hv_device *dev = host_dev->dev;

        stor_dev = get_in_stor_device(dev);
        host = stor_dev->host;

        vm_srb = &cmd_request->vstor_packet.vm_srb;
        if (cmd_request->bounce_sgl_count) {
                if (vm_srb->data_in == READ_TYPE)
                        copy_from_bounce_buffer(scsi_sglist(scmnd),
                                        cmd_request->bounce_sgl,
                                        scsi_sg_count(scmnd),
                                        cmd_request->bounce_sgl_count);
                destroy_bounce_buffer(cmd_request->bounce_sgl,
                                        cmd_request->bounce_sgl_count);
        }

        scmnd->result = vm_srb->scsi_status;

        if (scmnd->result) {
                if (scsi_normalize_sense(scmnd->sense_buffer,
                                SCSI_SENSE_BUFFERSIZE, &sense_hdr))
                        scsi_print_sense_hdr("storvsc", &sense_hdr);
        }

        if (vm_srb->srb_status != SRB_STATUS_SUCCESS)
                storvsc_handle_error(vm_srb, scmnd, host, sense_hdr.asc,
                                         sense_hdr.ascq);

        scsi_set_resid(scmnd,
                cmd_request->data_buffer.len -
                vm_srb->data_transfer_length);

        scsi_done_fn = scmnd->scsi_done;

        scmnd->host_scribble = NULL;
        scmnd->scsi_done = NULL;

        scsi_done_fn(scmnd);

        mempool_free(cmd_request, memp->request_mempool);
}

static void storvsc_on_io_completion(struct hv_device *device,
                                  struct vstor_packet *vstor_packet,
                                  struct storvsc_cmd_request *request)
{
        struct storvsc_device *stor_device;
        struct vstor_packet *stor_pkt;

        stor_device = hv_get_drvdata(device);
        stor_pkt = &request->vstor_packet;

        /*
         * The current SCSI handling on the host side does
         * not correctly handle:
         * INQUIRY command with page code parameter set to 0x80
         * MODE_SENSE command with cmd[2] == 0x1c
         *
         * Setup srb and scsi status so this won't be fatal.
         * We do this so we can distinguish truly fatal failues
         * (srb status == 0x4) and off-line the device in that case.
         */

        if ((stor_pkt->vm_srb.cdb[0] == INQUIRY) ||
           (stor_pkt->vm_srb.cdb[0] == MODE_SENSE)) {
                vstor_packet->vm_srb.scsi_status = 0;
                vstor_packet->vm_srb.srb_status = SRB_STATUS_SUCCESS;
        }


        /* Copy over the status...etc */
        stor_pkt->vm_srb.scsi_status = vstor_packet->vm_srb.scsi_status;
        stor_pkt->vm_srb.srb_status = vstor_packet->vm_srb.srb_status;
        stor_pkt->vm_srb.sense_info_length =
        vstor_packet->vm_srb.sense_info_length;

        if (vstor_packet->vm_srb.scsi_status != 0 ||
                vstor_packet->vm_srb.srb_status != SRB_STATUS_SUCCESS){
                dev_warn(&device->device,
                         "cmd 0x%x scsi status 0x%x srb status 0x%x\n",
                         stor_pkt->vm_srb.cdb[0],
                         vstor_packet->vm_srb.scsi_status,
                         vstor_packet->vm_srb.srb_status);
        }

        if ((vstor_packet->vm_srb.scsi_status & 0xFF) == 0x02) {
                /* CHECK_CONDITION */
                if (vstor_packet->vm_srb.srb_status &
                        SRB_STATUS_AUTOSENSE_VALID) {
                        /* autosense data available */
                        dev_warn(&device->device,
                                 "stor pkt %p autosense data valid - len %d\n",
                                 request,
                                 vstor_packet->vm_srb.sense_info_length);

                        memcpy(request->sense_buffer,
                               vstor_packet->vm_srb.sense_data,
                               vstor_packet->vm_srb.sense_info_length);

                }
        }

        stor_pkt->vm_srb.data_transfer_length =
        vstor_packet->vm_srb.data_transfer_length;

        storvsc_command_completion(request);

        if (atomic_dec_and_test(&stor_device->num_outstanding_req) &&
                stor_device->drain_notify)
                wake_up(&stor_device->waiting_to_drain);


}

static void storvsc_on_receive(struct hv_device *device,
                             struct vstor_packet *vstor_packet,
                             struct storvsc_cmd_request *request)
{
        struct storvsc_scan_work *work;
        struct storvsc_device *stor_device;

        switch (vstor_packet->operation) {
        case VSTOR_OPERATION_COMPLETE_IO:
                storvsc_on_io_completion(device, vstor_packet, request);
                break;

        case VSTOR_OPERATION_REMOVE_DEVICE:
        case VSTOR_OPERATION_ENUMERATE_BUS:
                stor_device = get_in_stor_device(device);
                work = kmalloc(sizeof(struct storvsc_scan_work), GFP_ATOMIC);
                if (!work)
                        return;

                INIT_WORK(&work->work, storvsc_bus_scan);
                work->host = stor_device->host;
                schedule_work(&work->work);
                break;

        default:
                break;
        }
}

static void storvsc_on_channel_callback(void *context)
{
        struct hv_device *device = (struct hv_device *)context;
        struct storvsc_device *stor_device;
        u32 bytes_recvd;
        u64 request_id;
        unsigned char packet[ALIGN(sizeof(struct vstor_packet), 8)];
        struct storvsc_cmd_request *request;
        int ret;


        stor_device = get_in_stor_device(device);
        if (!stor_device)
                return;

        do {
                ret = vmbus_recvpacket(device->channel, packet,
                                       ALIGN(sizeof(struct vstor_packet), 8),
                                       &bytes_recvd, &request_id);
                if (ret == 0 && bytes_recvd > 0) {

                        request = (struct storvsc_cmd_request *)
                                        (unsigned long)request_id;

                        if ((request == &stor_device->init_request) ||
                            (request == &stor_device->reset_request)) {

                                memcpy(&request->vstor_packet, packet,
                                       sizeof(struct vstor_packet));
                                complete(&request->wait_event);
                        } else {
                                storvsc_on_receive(device,
                                                (struct vstor_packet *)packet,
                                                request);
                        }
                } else {
                        break;
                }
        } while (1);

        return;
}

static int storvsc_connect_to_vsp(struct hv_device *device, u32 ring_size)
{
        struct vmstorage_channel_properties props;
        int ret;

        memset(&props, 0, sizeof(struct vmstorage_channel_properties));

        ret = vmbus_open(device->channel,
                         ring_size,
                         ring_size,
                         (void *)&props,
                         sizeof(struct vmstorage_channel_properties),
                         storvsc_on_channel_callback, device);

        if (ret != 0)
                return ret;

        ret = storvsc_channel_init(device);

        return ret;
}

static int storvsc_dev_remove(struct hv_device *device)
{
        struct storvsc_device *stor_device;
        unsigned long flags;

        stor_device = hv_get_drvdata(device);

        spin_lock_irqsave(&device->channel->inbound_lock, flags);
        stor_device->destroy = true;
        spin_unlock_irqrestore(&device->channel->inbound_lock, flags);

        /*
         * At this point, all outbound traffic should be disable. We
         * only allow inbound traffic (responses) to proceed so that
         * outstanding requests can be completed.
         */

        storvsc_wait_to_drain(stor_device);

        /*
         * Since we have already drained, we don't need to busy wait
         * as was done in final_release_stor_device()
         * Note that we cannot set the ext pointer to NULL until
         * we have drained - to drain the outgoing packets, we need to
         * allow incoming packets.
         */
        spin_lock_irqsave(&device->channel->inbound_lock, flags);
        hv_set_drvdata(device, NULL);
        spin_unlock_irqrestore(&device->channel->inbound_lock, flags);

        /* Close the channel */
        vmbus_close(device->channel);

        kfree(stor_device);
        return 0;
}

static int storvsc_do_io(struct hv_device *device,
                              struct storvsc_cmd_request *request)
{
        struct storvsc_device *stor_device;
        struct vstor_packet *vstor_packet;
        int ret = 0;

        vstor_packet = &request->vstor_packet;
        stor_device = get_out_stor_device(device);

        if (!stor_device)
                return -ENODEV;


        request->device  = device;


        vstor_packet->flags |= REQUEST_COMPLETION_FLAG;

        vstor_packet->vm_srb.length = sizeof(struct vmscsi_request);


        vstor_packet->vm_srb.sense_info_length = STORVSC_SENSE_BUFFER_SIZE;


        vstor_packet->vm_srb.data_transfer_length =
        request->data_buffer.len;

        vstor_packet->operation = VSTOR_OPERATION_EXECUTE_SRB;

        if (request->data_buffer.len) {
                ret = vmbus_sendpacket_multipagebuffer(device->channel,
                                &request->data_buffer,
                                vstor_packet,
                                sizeof(struct vstor_packet),
                                (unsigned long)request);
        } else {
                ret = vmbus_sendpacket(device->channel, vstor_packet,
                               sizeof(struct vstor_packet),
                               (unsigned long)request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        }

        if (ret != 0)
                return ret;

        atomic_inc(&stor_device->num_outstanding_req);

        return ret;
}

static int storvsc_device_alloc(struct scsi_device *sdevice)
{
        struct stor_mem_pools *memp;
        int number = STORVSC_MIN_BUF_NR;

        memp = kzalloc(sizeof(struct stor_mem_pools), GFP_KERNEL);
        if (!memp)
                return -ENOMEM;

        memp->request_pool =
                kmem_cache_create(dev_name(&sdevice->sdev_dev),
                                sizeof(struct storvsc_cmd_request), 0,
                                SLAB_HWCACHE_ALIGN, NULL);

        if (!memp->request_pool)
                goto err0;

        memp->request_mempool = mempool_create(number, mempool_alloc_slab,
                                                mempool_free_slab,
                                                memp->request_pool);

        if (!memp->request_mempool)
                goto err1;

        sdevice->hostdata = memp;

        return 0;

err1:
        kmem_cache_destroy(memp->request_pool);

err0:
        kfree(memp);
        return -ENOMEM;
}

static void storvsc_device_destroy(struct scsi_device *sdevice)
{
        struct stor_mem_pools *memp = sdevice->hostdata;

        if (!memp)
                return;

        mempool_destroy(memp->request_mempool);
        kmem_cache_destroy(memp->request_pool);
        kfree(memp);
        sdevice->hostdata = NULL;
}

static int storvsc_device_configure(struct scsi_device *sdevice)
{
        scsi_adjust_queue_depth(sdevice, MSG_SIMPLE_TAG,
                                STORVSC_MAX_IO_REQUESTS);

        blk_queue_max_segment_size(sdevice->request_queue, PAGE_SIZE);

        blk_queue_bounce_limit(sdevice->request_queue, BLK_BOUNCE_ANY);

        sdevice->no_write_same = 1;

        return 0;
}

static int storvsc_get_chs(struct scsi_device *sdev, struct block_device * bdev,
                           sector_t capacity, int *info)
{
        sector_t nsect = capacity;
        sector_t cylinders = nsect;
        int heads, sectors_pt;

        /*
         * We are making up these values; let us keep it simple.
         */
        heads = 0xff;
        sectors_pt = 0x3f;      /* Sectors per track */
        sector_div(cylinders, heads * sectors_pt);
        if ((sector_t)(cylinders + 1) * heads * sectors_pt < nsect)
                cylinders = 0xffff;

        info[0] = heads;
        info[1] = sectors_pt;
        info[2] = (int)cylinders;

        return 0;
}

static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
{
        struct hv_host_device *host_dev = shost_priv(scmnd->device->host);
        struct hv_device *device = host_dev->dev;

        struct storvsc_device *stor_device;
        struct storvsc_cmd_request *request;
        struct vstor_packet *vstor_packet;
        int ret, t;


        stor_device = get_out_stor_device(device);
        if (!stor_device)
                return FAILED;

        request = &stor_device->reset_request;
        vstor_packet = &request->vstor_packet;

        init_completion(&request->wait_event);

        vstor_packet->operation = VSTOR_OPERATION_RESET_BUS;
        vstor_packet->flags = REQUEST_COMPLETION_FLAG;
        vstor_packet->vm_srb.path_id = stor_device->path_id;

        ret = vmbus_sendpacket(device->channel, vstor_packet,
                               sizeof(struct vstor_packet),
                               (unsigned long)&stor_device->reset_request,
                               VM_PKT_DATA_INBAND,
                               VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (ret != 0)
                return FAILED;

        t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
        if (t == 0)
                return TIMEOUT_ERROR;


        /*
         * At this point, all outstanding requests in the adapter
         * should have been flushed out and return to us
         * There is a potential race here where the host may be in
         * the process of responding when we return from here.
         * Just wait for all in-transit packets to be accounted for
         * before we return from here.
         */
        storvsc_wait_to_drain(stor_device);

        return SUCCESS;
}

/*
 * The host guarantees to respond to each command, although I/O latencies might
 * be unbounded on Azure.  Reset the timer unconditionally to give the host a
 * chance to perform EH.
 */
static enum blk_eh_timer_return storvsc_eh_timed_out(struct scsi_cmnd *scmnd)
{
        return BLK_EH_RESET_TIMER;
}

static bool storvsc_scsi_cmd_ok(struct scsi_cmnd *scmnd)
{
        bool allowed = true;
        u8 scsi_op = scmnd->cmnd[0];

        switch (scsi_op) {
        /* the host does not handle WRITE_SAME, log accident usage */
        case WRITE_SAME:
        /*
         * smartd sends this command and the host does not handle
         * this. So, don't send it.
         */
        case SET_WINDOW:
                scmnd->result = ILLEGAL_REQUEST << 16;
                allowed = false;
                break;
        default:
                break;
        }
        return allowed;
}

static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
{
        int ret;
        struct hv_host_device *host_dev = shost_priv(host);
        struct hv_device *dev = host_dev->dev;
        struct storvsc_cmd_request *cmd_request;
        unsigned int request_size = 0;
        int i;
        struct scatterlist *sgl;
        unsigned int sg_count = 0;
        struct vmscsi_request *vm_srb;
        struct stor_mem_pools *memp = scmnd->device->hostdata;

        if (!storvsc_scsi_cmd_ok(scmnd)) {
                scmnd->scsi_done(scmnd);
                return 0;
        }

        request_size = sizeof(struct storvsc_cmd_request);

        cmd_request = mempool_alloc(memp->request_mempool,
                                       GFP_ATOMIC);

        /*
         * We might be invoked in an interrupt context; hence
         * mempool_alloc() can fail.
         */
        if (!cmd_request)
                return SCSI_MLQUEUE_DEVICE_BUSY;

        memset(cmd_request, 0, sizeof(struct storvsc_cmd_request));

        /* Setup the cmd request */
        cmd_request->cmd = scmnd;

        scmnd->host_scribble = (unsigned char *)cmd_request;

        vm_srb = &cmd_request->vstor_packet.vm_srb;


        /* Build the SRB */
        switch (scmnd->sc_data_direction) {
        case DMA_TO_DEVICE:
                vm_srb->data_in = WRITE_TYPE;
                break;
        case DMA_FROM_DEVICE:
                vm_srb->data_in = READ_TYPE;
                break;
        default:
                vm_srb->data_in = UNKNOWN_TYPE;
                break;
        }


        vm_srb->port_number = host_dev->port;
        vm_srb->path_id = scmnd->device->channel;
        vm_srb->target_id = scmnd->device->id;
        vm_srb->lun = scmnd->device->lun;

        vm_srb->cdb_length = scmnd->cmd_len;

        memcpy(vm_srb->cdb, scmnd->cmnd, vm_srb->cdb_length);

        cmd_request->sense_buffer = scmnd->sense_buffer;


        cmd_request->data_buffer.len = scsi_bufflen(scmnd);
        if (scsi_sg_count(scmnd)) {
                sgl = (struct scatterlist *)scsi_sglist(scmnd);
                sg_count = scsi_sg_count(scmnd);

                /* check if we need to bounce the sgl */
                if (do_bounce_buffer(sgl, scsi_sg_count(scmnd)) != -1) {
                        cmd_request->bounce_sgl =
                                create_bounce_buffer(sgl, scsi_sg_count(scmnd),
                                                     scsi_bufflen(scmnd),
                                                     vm_srb->data_in);
                        if (!cmd_request->bounce_sgl) {
                                ret = SCSI_MLQUEUE_HOST_BUSY;
                                goto queue_error;
                        }

                        cmd_request->bounce_sgl_count =
                                ALIGN(scsi_bufflen(scmnd), PAGE_SIZE) >>
                                        PAGE_SHIFT;

                        if (vm_srb->data_in == WRITE_TYPE)
                                copy_to_bounce_buffer(sgl,
                                        cmd_request->bounce_sgl,
                                        scsi_sg_count(scmnd));

                        sgl = cmd_request->bounce_sgl;
                        sg_count = cmd_request->bounce_sgl_count;
                }

                cmd_request->data_buffer.offset = sgl[0].offset;

                for (i = 0; i < sg_count; i++)
                        cmd_request->data_buffer.pfn_array[i] =
                                page_to_pfn(sg_page((&sgl[i])));

        } else if (scsi_sglist(scmnd)) {
                cmd_request->data_buffer.offset =
                        virt_to_phys(scsi_sglist(scmnd)) & (PAGE_SIZE-1);
                cmd_request->data_buffer.pfn_array[0] =
                        virt_to_phys(scsi_sglist(scmnd)) >> PAGE_SHIFT;
        }

        /* Invokes the vsc to start an IO */
        ret = storvsc_do_io(dev, cmd_request);

        if (ret == -EAGAIN) {
                /* no more space */

                if (cmd_request->bounce_sgl_count) {
                        destroy_bounce_buffer(cmd_request->bounce_sgl,
                                        cmd_request->bounce_sgl_count);

                        ret = SCSI_MLQUEUE_DEVICE_BUSY;
                        goto queue_error;
                }
        }

        return 0;

queue_error:
        mempool_free(cmd_request, memp->request_mempool);
        scmnd->host_scribble = NULL;
        return ret;
}

static struct scsi_host_template scsi_driver = {
        .module =               THIS_MODULE,
        .name =                 "storvsc_host_t",
        .bios_param =           storvsc_get_chs,
        .queuecommand =         storvsc_queuecommand,
        .eh_host_reset_handler =        storvsc_host_reset_handler,
        .eh_timed_out =         storvsc_eh_timed_out,
        .slave_alloc =          storvsc_device_alloc,
        .slave_destroy =        storvsc_device_destroy,
        .slave_configure =      storvsc_device_configure,
        .cmd_per_lun =          1,
        /* 64 max_queue * 1 target */
        .can_queue =            STORVSC_MAX_IO_REQUESTS*STORVSC_MAX_TARGETS,
        .this_id =              -1,
        /* no use setting to 0 since ll_blk_rw reset it to 1 */
        /* currently 32 */
        .sg_tablesize =         MAX_MULTIPAGE_BUFFER_COUNT,
        .use_clustering =       DISABLE_CLUSTERING,
        /* Make sure we dont get a sg segment crosses a page boundary */
        .dma_boundary =         PAGE_SIZE-1,
        .no_write_same =        1,
};

enum {
        SCSI_GUID,
        IDE_GUID,
};

static const struct hv_vmbus_device_id id_table[] = {
        /* SCSI guid */
        { HV_SCSI_GUID,
          .driver_data = SCSI_GUID
        },
        /* IDE guid */
        { HV_IDE_GUID,
          .driver_data = IDE_GUID
        },
        { },
};

MODULE_DEVICE_TABLE(vmbus, id_table);

static int storvsc_probe(struct hv_device *device,
                        const struct hv_vmbus_device_id *dev_id)
{
        int ret;
        struct Scsi_Host *host;
        struct hv_host_device *host_dev;
        bool dev_is_ide = ((dev_id->driver_data == IDE_GUID) ? true : false);
        int target = 0;
        struct storvsc_device *stor_device;

        host = scsi_host_alloc(&scsi_driver,
                               sizeof(struct hv_host_device));
        if (!host)
                return -ENOMEM;

        host_dev = shost_priv(host);
        memset(host_dev, 0, sizeof(struct hv_host_device));

        host_dev->port = host->host_no;
        host_dev->dev = device;


        stor_device = kzalloc(sizeof(struct storvsc_device), GFP_KERNEL);
        if (!stor_device) {
                ret = -ENOMEM;
                goto err_out0;
        }

        stor_device->destroy = false;
        init_waitqueue_head(&stor_device->waiting_to_drain);
        stor_device->device = device;
        stor_device->host = host;
        hv_set_drvdata(device, stor_device);

        stor_device->port_number = host->host_no;
        ret = storvsc_connect_to_vsp(device, storvsc_ringbuffer_size);
        if (ret)
                goto err_out1;

        host_dev->path = stor_device->path_id;
        host_dev->target = stor_device->target_id;

        /* max # of devices per target */
        host->max_lun = STORVSC_MAX_LUNS_PER_TARGET;
        /* max # of targets per channel */
        host->max_id = STORVSC_MAX_TARGETS;
        /* max # of channels */
        host->max_channel = STORVSC_MAX_CHANNELS - 1;
        /* max cmd length */
        host->max_cmd_len = STORVSC_MAX_CMD_LEN;

        /* Register the HBA and start the scsi bus scan */
        ret = scsi_add_host(host, &device->device);
        if (ret != 0)
                goto err_out2;

        if (!dev_is_ide) {
                scsi_scan_host(host);
        } else {
                target = (device->dev_instance.b[5] << 8 |
                         device->dev_instance.b[4]);
                ret = scsi_add_device(host, 0, target, 0);
                if (ret) {
                        scsi_remove_host(host);
                        goto err_out2;
                }
        }
        return 0;

err_out2:
        /*
         * Once we have connected with the host, we would need to
         * to invoke storvsc_dev_remove() to rollback this state and
         * this call also frees up the stor_device; hence the jump around
         * err_out1 label.
         */
        storvsc_dev_remove(device);
        goto err_out0;

err_out1:
        kfree(stor_device);

err_out0:
        scsi_host_put(host);
        return ret;
}

static int storvsc_remove(struct hv_device *dev)
{
        struct storvsc_device *stor_device = hv_get_drvdata(dev);
        struct Scsi_Host *host = stor_device->host;

        scsi_remove_host(host);
        storvsc_dev_remove(dev);
        scsi_host_put(host);

        return 0;
}

static struct hv_driver storvsc_drv = {
        .name = KBUILD_MODNAME,
        .id_table = id_table,
        .probe = storvsc_probe,
        .remove = storvsc_remove,
};

static int __init storvsc_drv_init(void)
{
        u32 max_outstanding_req_per_channel;

        /*
         * Divide the ring buffer data size (which is 1 page less
         * than the ring buffer size since that page is reserved for
         * the ring buffer indices) by the max request size (which is
         * vmbus_channel_packet_multipage_buffer + struct vstor_packet + u64)
         */
        max_outstanding_req_per_channel =
                ((storvsc_ringbuffer_size - PAGE_SIZE) /
                ALIGN(MAX_MULTIPAGE_BUFFER_PACKET +
                sizeof(struct vstor_packet) + sizeof(u64),
                sizeof(u64)));

        if (max_outstanding_req_per_channel <
            STORVSC_MAX_IO_REQUESTS)
                return -EINVAL;

        return vmbus_driver_register(&storvsc_drv);
}

static void __exit storvsc_drv_exit(void)
{
        vmbus_driver_unregister(&storvsc_drv);
}

MODULE_LICENSE("GPL");
MODULE_VERSION(HV_DRV_VERSION);
MODULE_DESCRIPTION("Microsoft Hyper-V virtual storage driver");
module_init(storvsc_drv_init);
module_exit(storvsc_drv_exit);