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bsg.c

/*
 * bsg.c - block layer implementation of the sg v4 interface
 *
 * Copyright (C) 2004 Jens Axboe <axboe@suse.de> SUSE Labs
 * Copyright (C) 2004 Peter M. Jones <pjones@redhat.com>
 *
 *  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/percpu.h>
#include <linux/uio.h>
#include <linux/idr.h>
#include <linux/bsg.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 minor;
      int queued_cmds;
      int done_cmds;
      wait_queue_head_t wq_done;
      wait_queue_head_t wq_free;
      char name[BUS_ID_SIZE];
      int max_queue;
      unsigned long flags;
};

enum {
      BSG_F_BLOCK       = 1,
      BSG_F_WRITE_PERM  = 2,
};

#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, __FUNCTION__, ##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, int has_write_perm)
{
      memset(rq->cmd, 0, BLK_MAX_CDB); /* ATAPI hates garbage after CDB */

      if (copy_from_user(rq->cmd, (void *)(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 = (hdr->timeout * HZ) / 1000;
      if (!rq->timeout)
            rq->timeout = q->sg_timeout;
      if (!rq->timeout)
            rq->timeout = BLK_DEFAULT_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;
      if (hdr->request_len > BLK_MAX_CDB)
            return -EINVAL;
      if (hdr->dout_xfer_len > (q->max_sectors << 9) ||
          hdr->din_xfer_len > (q->max_sectors << 9))
            return -EIO;

      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)
{
      struct request_queue *q = bd->queue;
      struct request *rq, *next_rq = NULL;
      int ret, rw;
      unsigned int dxfer_len;
      void *dxferp = NULL;

      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 seperately 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, test_bit(BSG_F_WRITE_PERM,
                                           &bd->flags));
      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;

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

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

      if (dxfer_len) {
            ret = blk_rq_map_user(q, rq, dxferp, dxfer_len);
            if (ret)
                  goto out;
      }
      return rq;
out:
      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)
{
      rq->sense = bc->sense;
      rq->sense_len = 0;

      /*
       * 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, 1, 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_entry(bd->done_list.next, 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 %u\n", rq, bio, rq->errors);
      /*
       * fill in all the output members
       */
      hdr->device_status = status_byte(rq->errors);
      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*)(unsigned long)hdr->response,
                           rq->sense, len);
            if (!ret)
                  hdr->response_len = len;
            else
                  ret = -EFAULT;
      }

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

      blk_rq_unmap_user(bio);
      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);

      set_bit(BSG_F_BLOCK, &bd->flags);

      /*
       * 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);
}

static inline void bsg_set_write_perm(struct bsg_device *bd, struct file *file)
{
      if (file->f_mode & FMODE_WRITE)
            set_bit(BSG_F_WRITE_PERM, &bd->flags);
      else
            clear_bit(BSG_F_WRITE_PERM, &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 || (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)
{
      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);
            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);
      bsg_set_write_perm(bd, file);

      bytes_written = 0;
      ret = __bsg_write(bd, buf, count, &bytes_written);
      *ppos = bytes_written;

      /*
       * return bytes written on non-fatal errors
       */
      if (!bytes_written || (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 int bsg_put_device(struct bsg_device *bd)
{
      int ret = 0;

      mutex_lock(&bsg_mutex);

      if (!atomic_dec_and_test(&bd->ref_count))
            goto out;

      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);

      blk_put_queue(bd->queue);
      hlist_del(&bd->dev_list);
      kfree(bd);
out:
      mutex_unlock(&bsg_mutex);
      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

      bd = bsg_alloc_device();
      if (!bd)
            return ERR_PTR(-ENOMEM);

      bd->queue = rq;
      kobject_get(&rq->kobj);
      bsg_set_block(bd, file);

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

      strncpy(bd->name, rq->bsg_dev.class_dev->class_id, 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 bsg_device *bd = NULL;
      struct hlist_node *entry;

      mutex_lock(&bsg_mutex);

      hlist_for_each(entry, bsg_dev_idx_hash(minor)) {
            bd = hlist_entry(entry, struct bsg_device, dev_list);
            if (bd->minor == minor) {
                  atomic_inc(&bd->ref_count);
                  break;
            }

            bd = NULL;
      }

      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;

      bd = __bsg_get_device(iminor(inode));
      if (bd)
            return bd;

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

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

      return bsg_add_device(inode, bcd->queue, file);
}

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

      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(file, bd->queue, NULL, cmd, uarg);
      }
      case SG_IO: {
            struct request *rq;
            struct bio *bio, *bidi_bio = NULL;
            struct sg_io_v4 hdr;

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

            rq = bsg_map_hdr(bd, &hdr);
            if (IS_ERR(rq))
                  return PTR_ERR(rq);

            bio = rq->bio;
            if (rq->next_rq)
                  bidi_bio = rq->next_rq->bio;
            blk_execute_rq(bd->queue, NULL, rq, 0);
            blk_complete_sgv4_hdr_rq(rq, &hdr, bio, bidi_bio);

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

            return 0;
      }
      /*
       * 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,
};

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);
      sysfs_remove_link(&q->kobj, "bsg");
      class_device_unregister(bcd->class_dev);
      put_device(bcd->dev);
      bcd->class_dev = NULL;
      bcd->dev = NULL;
      mutex_unlock(&bsg_mutex);
}
EXPORT_SYMBOL_GPL(bsg_unregister_queue);

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

      if (name)
            devname = name;
      else
            devname = gdev->bus_id;

      /*
       * 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->dev = get_device(gdev);
      dev = MKDEV(bsg_major, bcd->minor);
      class_dev = class_device_create(bsg_class, NULL, dev, gdev, "%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:
      class_device_unregister(class_dev);
put_dev:
      put_device(gdev);
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 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;
      }

      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);

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