bsg.c

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/*
 * bsg.c - block layer implementation of the sg v4 interface
 *
 * Copyright (C) 2004 Jens Axboe <[email protected]> SUSE Labs
 * Copyright (C) 2004 Peter M. Jones <[email protected]>
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License version 2.  See the file "COPYING" in the main directory of this
 *  archive for more details.
 *
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/blkdev.h>
#include <linux/poll.h>
#include <linux/cdev.h>
#include <linux/jiffies.h>
#include <linux/percpu.h>
#include <linux/uio.h>
#include <linux/idr.h>
#include <linux/bsg.h>
#include <linux/slab.h>

#include <scsi/scsi.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/sg.h>

#define BSG_DESCRIPTION "Block layer SCSI generic (bsg) driver"
#define BSG_VERSION "0.4"

struct bsg_device {
    struct request_queue *queue;
    spinlock_t lock;
    struct list_head busy_list;
    struct list_head done_list;
    struct hlist_node dev_list;
    atomic_t ref_count;
    int queued_cmds;
    int done_cmds;
    wait_queue_head_t wq_done;
    wait_queue_head_t wq_free;
    char name[20];
    int max_queue;
    unsigned long flags;
};

enum {
    BSG_F_BLOCK     = 1,
};

#define BSG_DEFAULT_CMDS    64
#define BSG_MAX_DEVS        32768

#undef BSG_DEBUG

#ifdef BSG_DEBUG
#define dprintk(fmt, args...) printk(KERN_ERR "%s: " fmt, __func__, ##args)
#else
#define dprintk(fmt, args...)
#endif

static DEFINE_MUTEX(bsg_mutex);
static DEFINE_IDR(bsg_minor_idr);

#define BSG_LIST_ARRAY_SIZE 8
static struct hlist_head bsg_device_list[BSG_LIST_ARRAY_SIZE];

static struct class *bsg_class;
static int bsg_major;

static struct kmem_cache *bsg_cmd_cachep;

/*
 * our internal command type
 */
struct bsg_command {
    struct bsg_device *bd;
    struct list_head list;
    struct request *rq;
    struct bio *bio;
    struct bio *bidi_bio;
    int err;
    struct sg_io_v4 hdr;
    char sense[SCSI_SENSE_BUFFERSIZE];
};

static void bsg_free_command(struct bsg_command *bc)
{
    struct bsg_device *bd = bc->bd;
    unsigned long flags;

    kmem_cache_free(bsg_cmd_cachep, bc);

    spin_lock_irqsave(&bd->lock, flags);
    bd->queued_cmds--;
    spin_unlock_irqrestore(&bd->lock, flags);

    wake_up(&bd->wq_free);
}

static struct bsg_command *bsg_alloc_command(struct bsg_device *bd)
{
    struct bsg_command *bc = ERR_PTR(-EINVAL);

    spin_lock_irq(&bd->lock);

    if (bd->queued_cmds >= bd->max_queue)
        goto out;

    bd->queued_cmds++;
    spin_unlock_irq(&bd->lock);

    bc = kmem_cache_zalloc(bsg_cmd_cachep, GFP_KERNEL);
    if (unlikely(!bc)) {
        spin_lock_irq(&bd->lock);
        bd->queued_cmds--;
        bc = ERR_PTR(-ENOMEM);
        goto out;
    }

    bc->bd = bd;
    INIT_LIST_HEAD(&bc->list);
    dprintk("%s: returning free cmd %p\n", bd->name, bc);
    return bc;
out:
    spin_unlock_irq(&bd->lock);
    return bc;
}

static inline struct hlist_head *bsg_dev_idx_hash(int index)
{
    return &bsg_device_list[index & (BSG_LIST_ARRAY_SIZE - 1)];
}

static int bsg_io_schedule(struct bsg_device *bd)
{
    DEFINE_WAIT(wait);
    int ret = 0;

    spin_lock_irq(&bd->lock);

    BUG_ON(bd->done_cmds > bd->queued_cmds);

    /*
     * -ENOSPC or -ENODATA?  I'm going for -ENODATA, meaning "I have no
     * work to do", even though we return -ENOSPC after this same test
     * during bsg_write() -- there, it means our buffer can't have more
     * bsg_commands added to it, thus has no space left.
     */
    if (bd->done_cmds == bd->queued_cmds) {
        ret = -ENODATA;
        goto unlock;
    }

    if (!test_bit(BSG_F_BLOCK, &bd->flags)) {
        ret = -EAGAIN;
        goto unlock;
    }

    prepare_to_wait(&bd->wq_done, &wait, TASK_UNINTERRUPTIBLE);
    spin_unlock_irq(&bd->lock);
    io_schedule();
    finish_wait(&bd->wq_done, &wait);

    return ret;
unlock:
    spin_unlock_irq(&bd->lock);
    return ret;
}

static int blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,
                struct sg_io_v4 *hdr, struct bsg_device *bd,
                fmode_t has_write_perm)
{
    if (hdr->request_len > BLK_MAX_CDB) {
        rq->cmd = kzalloc(hdr->request_len, GFP_KERNEL);
        if (!rq->cmd)
            return -ENOMEM;
    }

    if (copy_from_user(rq->cmd, (void __user *)(unsigned long)hdr->request,
               hdr->request_len))
        return -EFAULT;

    if (hdr->subprotocol == BSG_SUB_PROTOCOL_SCSI_CMD) {
        if (blk_verify_command(rq->cmd, has_write_perm))
            return -EPERM;
    } else if (!capable(CAP_SYS_RAWIO))
        return -EPERM;

    /*
     * fill in request structure
     */
    rq->cmd_len = hdr->request_len;
    rq->cmd_type = REQ_TYPE_BLOCK_PC;

    rq->timeout = msecs_to_jiffies(hdr->timeout);
    if (!rq->timeout)
        rq->timeout = q->sg_timeout;
    if (!rq->timeout)
        rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
    if (rq->timeout < BLK_MIN_SG_TIMEOUT)
        rq->timeout = BLK_MIN_SG_TIMEOUT;

    return 0;
}

/*
 * Check if sg_io_v4 from user is allowed and valid
 */
static int
bsg_validate_sgv4_hdr(struct request_queue *q, struct sg_io_v4 *hdr, int *rw)
{
    int ret = 0;

    if (hdr->guard != 'Q')
        return -EINVAL;

    switch (hdr->protocol) {
    case BSG_PROTOCOL_SCSI:
        switch (hdr->subprotocol) {
        case BSG_SUB_PROTOCOL_SCSI_CMD:
        case BSG_SUB_PROTOCOL_SCSI_TRANSPORT:
            break;
        default:
            ret = -EINVAL;
        }
        break;
    default:
        ret = -EINVAL;
    }

    *rw = hdr->dout_xfer_len ? WRITE : READ;
    return ret;
}

/*
 * map sg_io_v4 to a request.
 */
static struct request *
bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t has_write_perm,
        u8 *sense)
{
    struct request_queue *q = bd->queue;
    struct request *rq, *next_rq = NULL;
    int ret, rw;
    unsigned int dxfer_len;
    void __user *dxferp = NULL;
    struct bsg_class_device *bcd = &q->bsg_dev;

    /* if the LLD has been removed then the bsg_unregister_queue will
     * eventually be called and the class_dev was freed, so we can no
     * longer use this request_queue. Return no such address.
     */
    if (!bcd->class_dev)
        return ERR_PTR(-ENXIO);

    dprintk("map hdr %llx/%u %llx/%u\n", (unsigned long long) hdr->dout_xferp,
        hdr->dout_xfer_len, (unsigned long long) hdr->din_xferp,
        hdr->din_xfer_len);

    ret = bsg_validate_sgv4_hdr(q, hdr, &rw);
    if (ret)
        return ERR_PTR(ret);

    /*
     * map scatter-gather elements separately and string them to request
     */
    rq = blk_get_request(q, rw, GFP_KERNEL);
    if (!rq)
        return ERR_PTR(-ENOMEM);
    ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, has_write_perm);
    if (ret)
        goto out;

    if (rw == WRITE && hdr->din_xfer_len) {
        if (!test_bit(QUEUE_FLAG_BIDI, &q->queue_flags)) {
            ret = -EOPNOTSUPP;
            goto out;
        }

        next_rq = blk_get_request(q, READ, GFP_KERNEL);
        if (!next_rq) {
            ret = -ENOMEM;
            goto out;
        }
        rq->next_rq = next_rq;
        next_rq->cmd_type = rq->cmd_type;

        dxferp = (void __user *)(unsigned long)hdr->din_xferp;
        ret =  blk_rq_map_user(q, next_rq, NULL, dxferp,
                       hdr->din_xfer_len, GFP_KERNEL);
        if (ret)
            goto out;
    }

    if (hdr->dout_xfer_len) {
        dxfer_len = hdr->dout_xfer_len;
        dxferp = (void __user *)(unsigned long)hdr->dout_xferp;
    } else if (hdr->din_xfer_len) {
        dxfer_len = hdr->din_xfer_len;
        dxferp = (void __user *)(unsigned long)hdr->din_xferp;
    } else
        dxfer_len = 0;

    if (dxfer_len) {
        ret = blk_rq_map_user(q, rq, NULL, dxferp, dxfer_len,
                      GFP_KERNEL);
        if (ret)
            goto out;
    }

    rq->sense = sense;
    rq->sense_len = 0;

    return rq;
out:
    if (rq->cmd != rq->__cmd)
        kfree(rq->cmd);
    blk_put_request(rq);
    if (next_rq) {
        blk_rq_unmap_user(next_rq->bio);
        blk_put_request(next_rq);
    }
    return ERR_PTR(ret);
}

/*
 * async completion call-back from the block layer, when scsi/ide/whatever
 * calls end_that_request_last() on a request
 */
static void bsg_rq_end_io(struct request *rq, int uptodate)
{
    struct bsg_command *bc = rq->end_io_data;
    struct bsg_device *bd = bc->bd;
    unsigned long flags;

    dprintk("%s: finished rq %p bc %p, bio %p stat %d\n",
        bd->name, rq, bc, bc->bio, uptodate);

    bc->hdr.duration = jiffies_to_msecs(jiffies - bc->hdr.duration);

    spin_lock_irqsave(&bd->lock, flags);
    list_move_tail(&bc->list, &bd->done_list);
    bd->done_cmds++;
    spin_unlock_irqrestore(&bd->lock, flags);

    wake_up(&bd->wq_done);
}

/*
 * do final setup of a 'bc' and submit the matching 'rq' to the block
 * layer for io
 */
static void bsg_add_command(struct bsg_device *bd, struct request_queue *q,
                struct bsg_command *bc, struct request *rq)
{
    int at_head = (0 == (bc->hdr.flags & BSG_FLAG_Q_AT_TAIL));

    /*
     * add bc command to busy queue and submit rq for io
     */
    bc->rq = rq;
    bc->bio = rq->bio;
    if (rq->next_rq)
        bc->bidi_bio = rq->next_rq->bio;
    bc->hdr.duration = jiffies;
    spin_lock_irq(&bd->lock);
    list_add_tail(&bc->list, &bd->busy_list);
    spin_unlock_irq(&bd->lock);

    dprintk("%s: queueing rq %p, bc %p\n", bd->name, rq, bc);

    rq->end_io_data = bc;
    blk_execute_rq_nowait(q, NULL, rq, at_head, bsg_rq_end_io);
}

static struct bsg_command *bsg_next_done_cmd(struct bsg_device *bd)
{
    struct bsg_command *bc = NULL;

    spin_lock_irq(&bd->lock);
    if (bd->done_cmds) {
        bc = list_first_entry(&bd->done_list, struct bsg_command, list);
        list_del(&bc->list);
        bd->done_cmds--;
    }
    spin_unlock_irq(&bd->lock);

    return bc;
}

/*
 * Get a finished command from the done list
 */
static struct bsg_command *bsg_get_done_cmd(struct bsg_device *bd)
{
    struct bsg_command *bc;
    int ret;

    do {
        bc = bsg_next_done_cmd(bd);
        if (bc)
            break;

        if (!test_bit(BSG_F_BLOCK, &bd->flags)) {
            bc = ERR_PTR(-EAGAIN);
            break;
        }

        ret = wait_event_interruptible(bd->wq_done, bd->done_cmds);
        if (ret) {
            bc = ERR_PTR(-ERESTARTSYS);
            break;
        }
    } while (1);

    dprintk("%s: returning done %p\n", bd->name, bc);

    return bc;
}

static int blk_complete_sgv4_hdr_rq(struct request *rq, struct sg_io_v4 *hdr,
                    struct bio *bio, struct bio *bidi_bio)
{
    int ret = 0;

    dprintk("rq %p bio %p 0x%x\n", rq, bio, rq->errors);
    /*
     * fill in all the output members
     */
    hdr->device_status = rq->errors & 0xff;
    hdr->transport_status = host_byte(rq->errors);
    hdr->driver_status = driver_byte(rq->errors);
    hdr->info = 0;
    if (hdr->device_status || hdr->transport_status || hdr->driver_status)
        hdr->info |= SG_INFO_CHECK;
    hdr->response_len = 0;

    if (rq->sense_len && hdr->response) {
        int len = min_t(unsigned int, hdr->max_response_len,
                    rq->sense_len);

        ret = copy_to_user((void __user *)(unsigned long)hdr->response,
                   rq->sense, len);
        if (!ret)
            hdr->response_len = len;
        else
            ret = -EFAULT;
    }

    if (rq->next_rq) {
        hdr->dout_resid = rq->resid_len;
        hdr->din_resid = rq->next_rq->resid_len;
        blk_rq_unmap_user(bidi_bio);
        blk_put_request(rq->next_rq);
    } else if (rq_data_dir(rq) == READ)
        hdr->din_resid = rq->resid_len;
    else
        hdr->dout_resid = rq->resid_len;

    /*
     * If the request generated a negative error number, return it
     * (providing we aren't already returning an error); if it's
     * just a protocol response (i.e. non negative), that gets
     * processed above.
     */
    if (!ret && rq->errors < 0)
        ret = rq->errors;

    blk_rq_unmap_user(bio);
    if (rq->cmd != rq->__cmd)
        kfree(rq->cmd);
    blk_put_request(rq);

    return ret;
}

static int bsg_complete_all_commands(struct bsg_device *bd)
{
    struct bsg_command *bc;
    int ret, tret;

    dprintk("%s: entered\n", bd->name);

    /*
     * wait for all commands to complete
     */
    ret = 0;
    do {
        ret = bsg_io_schedule(bd);
        /*
         * look for -ENODATA specifically -- we'll sometimes get
         * -ERESTARTSYS when we've taken a signal, but we can't
         * return until we're done freeing the queue, so ignore
         * it.  The signal will get handled when we're done freeing
         * the bsg_device.
         */
    } while (ret != -ENODATA);

    /*
     * discard done commands
     */
    ret = 0;
    do {
        spin_lock_irq(&bd->lock);
        if (!bd->queued_cmds) {
            spin_unlock_irq(&bd->lock);
            break;
        }
        spin_unlock_irq(&bd->lock);

        bc = bsg_get_done_cmd(bd);
        if (IS_ERR(bc))
            break;

        tret = blk_complete_sgv4_hdr_rq(bc->rq, &bc->hdr, bc->bio,
                        bc->bidi_bio);
        if (!ret)
            ret = tret;

        bsg_free_command(bc);
    } while (1);

    return ret;
}

static int
__bsg_read(char __user *buf, size_t count, struct bsg_device *bd,
       const struct iovec *iov, ssize_t *bytes_read)
{
    struct bsg_command *bc;
    int nr_commands, ret;

    if (count % sizeof(struct sg_io_v4))
        return -EINVAL;

    ret = 0;
    nr_commands = count / sizeof(struct sg_io_v4);
    while (nr_commands) {
        bc = bsg_get_done_cmd(bd);
        if (IS_ERR(bc)) {
            ret = PTR_ERR(bc);
            break;
        }

        /*
         * this is the only case where we need to copy data back
         * after completing the request. so do that here,
         * bsg_complete_work() cannot do that for us
         */
        ret = blk_complete_sgv4_hdr_rq(bc->rq, &bc->hdr, bc->bio,
                           bc->bidi_bio);

        if (copy_to_user(buf, &bc->hdr, sizeof(bc->hdr)))
            ret = -EFAULT;

        bsg_free_command(bc);

        if (ret)
            break;

        buf += sizeof(struct sg_io_v4);
        *bytes_read += sizeof(struct sg_io_v4);
        nr_commands--;
    }

    return ret;
}

static inline void bsg_set_block(struct bsg_device *bd, struct file *file)
{
    if (file->f_flags & O_NONBLOCK)
        clear_bit(BSG_F_BLOCK, &bd->flags);
    else
        set_bit(BSG_F_BLOCK, &bd->flags);
}

/*
 * Check if the error is a "real" error that we should return.
 */
static inline int err_block_err(int ret)
{
    if (ret && ret != -ENOSPC && ret != -ENODATA && ret != -EAGAIN)
        return 1;

    return 0;
}

static ssize_t
bsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    struct bsg_device *bd = file->private_data;
    int ret;
    ssize_t bytes_read;

    dprintk("%s: read %Zd bytes\n", bd->name, count);

    bsg_set_block(bd, file);

    bytes_read = 0;
    ret = __bsg_read(buf, count, bd, NULL, &bytes_read);
    *ppos = bytes_read;

    if (!bytes_read || err_block_err(ret))
        bytes_read = ret;

    return bytes_read;
}

static int __bsg_write(struct bsg_device *bd, const char __user *buf,
               size_t count, ssize_t *bytes_written,
               fmode_t has_write_perm)
{
    struct bsg_command *bc;
    struct request *rq;
    int ret, nr_commands;

    if (count % sizeof(struct sg_io_v4))
        return -EINVAL;

    nr_commands = count / sizeof(struct sg_io_v4);
    rq = NULL;
    bc = NULL;
    ret = 0;
    while (nr_commands) {
        struct request_queue *q = bd->queue;

        bc = bsg_alloc_command(bd);
        if (IS_ERR(bc)) {
            ret = PTR_ERR(bc);
            bc = NULL;
            break;
        }

        if (copy_from_user(&bc->hdr, buf, sizeof(bc->hdr))) {
            ret = -EFAULT;
            break;
        }

        /*
         * get a request, fill in the blanks, and add to request queue
         */
        rq = bsg_map_hdr(bd, &bc->hdr, has_write_perm, bc->sense);
        if (IS_ERR(rq)) {
            ret = PTR_ERR(rq);
            rq = NULL;
            break;
        }

        bsg_add_command(bd, q, bc, rq);
        bc = NULL;
        rq = NULL;
        nr_commands--;
        buf += sizeof(struct sg_io_v4);
        *bytes_written += sizeof(struct sg_io_v4);
    }

    if (bc)
        bsg_free_command(bc);

    return ret;
}

static ssize_t
bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
    struct bsg_device *bd = file->private_data;
    ssize_t bytes_written;
    int ret;

    dprintk("%s: write %Zd bytes\n", bd->name, count);

    bsg_set_block(bd, file);

    bytes_written = 0;
    ret = __bsg_write(bd, buf, count, &bytes_written,
              file->f_mode & FMODE_WRITE);

    *ppos = bytes_written;

    /*
     * return bytes written on non-fatal errors
     */
    if (!bytes_written || err_block_err(ret))
        bytes_written = ret;

    dprintk("%s: returning %Zd\n", bd->name, bytes_written);
    return bytes_written;
}

static struct bsg_device *bsg_alloc_device(void)
{
    struct bsg_device *bd;

    bd = kzalloc(sizeof(struct bsg_device), GFP_KERNEL);
    if (unlikely(!bd))
        return NULL;

    spin_lock_init(&bd->lock);

    bd->max_queue = BSG_DEFAULT_CMDS;

    INIT_LIST_HEAD(&bd->busy_list);
    INIT_LIST_HEAD(&bd->done_list);
    INIT_HLIST_NODE(&bd->dev_list);

    init_waitqueue_head(&bd->wq_free);
    init_waitqueue_head(&bd->wq_done);
    return bd;
}

static void bsg_kref_release_function(struct kref *kref)
{
    struct bsg_class_device *bcd =
        container_of(kref, struct bsg_class_device, ref);
    struct device *parent = bcd->parent;

    if (bcd->release)
        bcd->release(bcd->parent);

    put_device(parent);
}

static int bsg_put_device(struct bsg_device *bd)
{
    int ret = 0, do_free;
    struct request_queue *q = bd->queue;

    mutex_lock(&bsg_mutex);

    do_free = atomic_dec_and_test(&bd->ref_count);
    if (!do_free) {
        mutex_unlock(&bsg_mutex);
        goto out;
    }

    hlist_del(&bd->dev_list);
    mutex_unlock(&bsg_mutex);

    dprintk("%s: tearing down\n", bd->name);

    /*
     * close can always block
     */
    set_bit(BSG_F_BLOCK, &bd->flags);

    /*
     * correct error detection baddies here again. it's the responsibility
     * of the app to properly reap commands before close() if it wants
     * fool-proof error detection
     */
    ret = bsg_complete_all_commands(bd);

    kfree(bd);
out:
    kref_put(&q->bsg_dev.ref, bsg_kref_release_function);
    if (do_free)
        blk_put_queue(q);
    return ret;
}

static struct bsg_device *bsg_add_device(struct inode *inode,
                     struct request_queue *rq,
                     struct file *file)
{
    struct bsg_device *bd;
#ifdef BSG_DEBUG
    unsigned char buf[32];
#endif
    if (!blk_get_queue(rq))
        return ERR_PTR(-ENXIO);

    bd = bsg_alloc_device();
    if (!bd) {
        blk_put_queue(rq);
        return ERR_PTR(-ENOMEM);
    }

    bd->queue = rq;

    bsg_set_block(bd, file);

    atomic_set(&bd->ref_count, 1);
    mutex_lock(&bsg_mutex);
    hlist_add_head(&bd->dev_list, bsg_dev_idx_hash(iminor(inode)));

    strncpy(bd->name, dev_name(rq->bsg_dev.class_dev), sizeof(bd->name) - 1);
    dprintk("bound to <%s>, max queue %d\n",
        format_dev_t(buf, inode->i_rdev), bd->max_queue);

    mutex_unlock(&bsg_mutex);
    return bd;
}

static struct bsg_device *__bsg_get_device(int minor, struct request_queue *q)
{
    struct bsg_device *bd;
    struct hlist_node *entry;

    mutex_lock(&bsg_mutex);

    hlist_for_each_entry(bd, entry, bsg_dev_idx_hash(minor), dev_list) {
        if (bd->queue == q) {
            atomic_inc(&bd->ref_count);
            goto found;
        }
    }
    bd = NULL;
found:
    mutex_unlock(&bsg_mutex);
    return bd;
}

static struct bsg_device *bsg_get_device(struct inode *inode, struct file *file)
{
    struct bsg_device *bd;
    struct bsg_class_device *bcd;

    /*
     * find the class device
     */
    mutex_lock(&bsg_mutex);
    bcd = idr_find(&bsg_minor_idr, iminor(inode));
    if (bcd)
        kref_get(&bcd->ref);
    mutex_unlock(&bsg_mutex);

    if (!bcd)
        return ERR_PTR(-ENODEV);

    bd = __bsg_get_device(iminor(inode), bcd->queue);
    if (bd)
        return bd;

    bd = bsg_add_device(inode, bcd->queue, file);
    if (IS_ERR(bd))
        kref_put(&bcd->ref, bsg_kref_release_function);

    return bd;
}

static int bsg_open(struct inode *inode, struct file *file)
{
    struct bsg_device *bd;

    bd = bsg_get_device(inode, file);

    if (IS_ERR(bd))
        return PTR_ERR(bd);

    file->private_data = bd;
    return 0;
}

static int bsg_release(struct inode *inode, struct file *file)
{
    struct bsg_device *bd = file->private_data;

    file->private_data = NULL;
    return bsg_put_device(bd);
}

static unsigned int bsg_poll(struct file *file, poll_table *wait)
{
    struct bsg_device *bd = file->private_data;
    unsigned int mask = 0;

    poll_wait(file, &bd->wq_done, wait);
    poll_wait(file, &bd->wq_free, wait);

    spin_lock_irq(&bd->lock);
    if (!list_empty(&bd->done_list))
        mask |= POLLIN | POLLRDNORM;
    if (bd->queued_cmds < bd->max_queue)
        mask |= POLLOUT;
    spin_unlock_irq(&bd->lock);

    return mask;
}

static long bsg_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct bsg_device *bd = file->private_data;
    int __user *uarg = (int __user *) arg;
    int ret;

    switch (cmd) {
        /*
         * our own ioctls
         */
    case SG_GET_COMMAND_Q:
        return put_user(bd->max_queue, uarg);
    case SG_SET_COMMAND_Q: {
        int queue;

        if (get_user(queue, uarg))
            return -EFAULT;
        if (queue < 1)
            return -EINVAL;

        spin_lock_irq(&bd->lock);
        bd->max_queue = queue;
        spin_unlock_irq(&bd->lock);
        return 0;
    }

    /*
     * SCSI/sg ioctls
     */
    case SG_GET_VERSION_NUM:
    case SCSI_IOCTL_GET_IDLUN:
    case SCSI_IOCTL_GET_BUS_NUMBER:
    case SG_SET_TIMEOUT:
    case SG_GET_TIMEOUT:
    case SG_GET_RESERVED_SIZE:
    case SG_SET_RESERVED_SIZE:
    case SG_EMULATED_HOST:
    case SCSI_IOCTL_SEND_COMMAND: {
        void __user *uarg = (void __user *) arg;
        return scsi_cmd_ioctl(bd->queue, NULL, file->f_mode, cmd, uarg);
    }
    case SG_IO: {
        struct request *rq;
        struct bio *bio, *bidi_bio = NULL;
        struct sg_io_v4 hdr;
        int at_head;
        u8 sense[SCSI_SENSE_BUFFERSIZE];

        if (copy_from_user(&hdr, uarg, sizeof(hdr)))
            return -EFAULT;

        rq = bsg_map_hdr(bd, &hdr, file->f_mode & FMODE_WRITE, sense);
        if (IS_ERR(rq))
            return PTR_ERR(rq);

        bio = rq->bio;
        if (rq->next_rq)
            bidi_bio = rq->next_rq->bio;

        at_head = (0 == (hdr.flags & BSG_FLAG_Q_AT_TAIL));
        blk_execute_rq(bd->queue, NULL, rq, at_head);
        ret = blk_complete_sgv4_hdr_rq(rq, &hdr, bio, bidi_bio);

        if (copy_to_user(uarg, &hdr, sizeof(hdr)))
            return -EFAULT;

        return ret;
    }
    /*
     * block device ioctls
     */
    default:
#if 0
        return ioctl_by_bdev(bd->bdev, cmd, arg);
#else
        return -ENOTTY;
#endif
    }
}

static const struct file_operations bsg_fops = {
    .read       =   bsg_read,
    .write      =   bsg_write,
    .poll       =   bsg_poll,
    .open       =   bsg_open,
    .release    =   bsg_release,
    .unlocked_ioctl =   bsg_ioctl,
    .owner      =   THIS_MODULE,
    .llseek     =   default_llseek,
};

void bsg_unregister_queue(struct request_queue *q)
{
    struct bsg_class_device *bcd = &q->bsg_dev;

    if (!bcd->class_dev)
        return;

    mutex_lock(&bsg_mutex);
    idr_remove(&bsg_minor_idr, bcd->minor);
    if (q->kobj.sd)
        sysfs_remove_link(&q->kobj, "bsg");
    device_unregister(bcd->class_dev);
    bcd->class_dev = NULL;
    kref_put(&bcd->ref, bsg_kref_release_function);
    mutex_unlock(&bsg_mutex);
}
EXPORT_SYMBOL_GPL(bsg_unregister_queue);

int bsg_register_queue(struct request_queue *q, struct device *parent,
               const char *name, void (*release)(struct device *))
{
    struct bsg_class_device *bcd;
    dev_t dev;
    int ret, minor;
    struct device *class_dev = NULL;
    const char *devname;

    if (name)
        devname = name;
    else
        devname = dev_name(parent);

    /*
     * we need a proper transport to send commands, not a stacked device
     */
    if (!q->request_fn)
        return 0;

    bcd = &q->bsg_dev;
    memset(bcd, 0, sizeof(*bcd));

    mutex_lock(&bsg_mutex);

    ret = idr_pre_get(&bsg_minor_idr, GFP_KERNEL);
    if (!ret) {
        ret = -ENOMEM;
        goto unlock;
    }

    ret = idr_get_new(&bsg_minor_idr, bcd, &minor);
    if (ret < 0)
        goto unlock;

    if (minor >= BSG_MAX_DEVS) {
        printk(KERN_ERR "bsg: too many bsg devices\n");
        ret = -EINVAL;
        goto remove_idr;
    }

    bcd->minor = minor;
    bcd->queue = q;
    bcd->parent = get_device(parent);
    bcd->release = release;
    kref_init(&bcd->ref);
    dev = MKDEV(bsg_major, bcd->minor);
    class_dev = device_create(bsg_class, parent, dev, NULL, "%s", devname);
    if (IS_ERR(class_dev)) {
        ret = PTR_ERR(class_dev);
        goto put_dev;
    }
    bcd->class_dev = class_dev;

    if (q->kobj.sd) {
        ret = sysfs_create_link(&q->kobj, &bcd->class_dev->kobj, "bsg");
        if (ret)
            goto unregister_class_dev;
    }

    mutex_unlock(&bsg_mutex);
    return 0;

unregister_class_dev:
    device_unregister(class_dev);
put_dev:
    put_device(parent);
remove_idr:
    idr_remove(&bsg_minor_idr, minor);
unlock:
    mutex_unlock(&bsg_mutex);
    return ret;
}
EXPORT_SYMBOL_GPL(bsg_register_queue);

static struct cdev bsg_cdev;

static char *bsg_devnode(struct device *dev, umode_t *mode)
{
    return kasprintf(GFP_KERNEL, "bsg/%s", dev_name(dev));
}

static int __init bsg_init(void)
{
    int ret, i;
    dev_t devid;

    bsg_cmd_cachep = kmem_cache_create("bsg_cmd",
                sizeof(struct bsg_command), 0, 0, NULL);
    if (!bsg_cmd_cachep) {
        printk(KERN_ERR "bsg: failed creating slab cache\n");
        return -ENOMEM;
    }

    for (i = 0; i < BSG_LIST_ARRAY_SIZE; i++)
        INIT_HLIST_HEAD(&bsg_device_list[i]);

    bsg_class = class_create(THIS_MODULE, "bsg");
    if (IS_ERR(bsg_class)) {
        ret = PTR_ERR(bsg_class);
        goto destroy_kmemcache;
    }
    bsg_class->devnode = bsg_devnode;

    ret = alloc_chrdev_region(&devid, 0, BSG_MAX_DEVS, "bsg");
    if (ret)
        goto destroy_bsg_class;

    bsg_major = MAJOR(devid);

    cdev_init(&bsg_cdev, &bsg_fops);
    ret = cdev_add(&bsg_cdev, MKDEV(bsg_major, 0), BSG_MAX_DEVS);
    if (ret)
        goto unregister_chrdev;

    printk(KERN_INFO BSG_DESCRIPTION " version " BSG_VERSION
           " loaded (major %d)\n", bsg_major);
    return 0;
unregister_chrdev:
    unregister_chrdev_region(MKDEV(bsg_major, 0), BSG_MAX_DEVS);
destroy_bsg_class:
    class_destroy(bsg_class);
destroy_kmemcache:
    kmem_cache_destroy(bsg_cmd_cachep);
    return ret;
}

MODULE_AUTHOR("Jens Axboe");
MODULE_DESCRIPTION(BSG_DESCRIPTION);
MODULE_LICENSE("GPL");

device_initcall(bsg_init);