block, bfq: return nbytes and not zero from struct cftype .write() method

[mirror_ubuntu-bionic-kernel.git] / block / 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/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;
};

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 blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,
                                struct sg_io_v4 *hdr, struct bsg_device *bd,
                                fmode_t mode)
{
        struct scsi_request *req = scsi_req(rq);

        if (hdr->request_len > BLK_MAX_CDB) {
                req->cmd = kzalloc(hdr->request_len, GFP_KERNEL);
                if (!req->cmd)
                        return -ENOMEM;
        }

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

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

        /*
         * fill in request structure
         */
        req->cmd_len = hdr->request_len;

        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 sg_io_v4 *hdr, int *op)
{
        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;
        }

        *op = hdr->dout_xfer_len ? REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN;
        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 mode)
{
        struct request_queue *q = bd->queue;
        struct request *rq, *next_rq = NULL;
        int ret;
        unsigned int op, 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(hdr, &op);
        if (ret)
                return ERR_PTR(ret);

        /*
         * map scatter-gather elements separately and string them to request
         */
        rq = blk_get_request(q, op, GFP_KERNEL);
        if (IS_ERR(rq))
                return rq;

        ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, mode);
        if (ret)
                goto out;

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

                next_rq = blk_get_request(q, REQ_OP_SCSI_IN, GFP_KERNEL);
                if (IS_ERR(next_rq)) {
                        ret = PTR_ERR(next_rq);
                        next_rq = NULL;
                        goto out;
                }
                rq->next_rq = next_rq;

                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;
        }

        return rq;
out:
        scsi_req_free_cmd(scsi_req(rq));
        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, blk_status_t status)
{
        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\n",
                bd->name, rq, bc, bc->bio);

        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)
{
        struct scsi_request *req = scsi_req(rq);
        int ret = 0;

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

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

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

        if (rq->next_rq) {
                hdr->dout_resid = req->resid_len;
                hdr->din_resid = scsi_req(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 = req->resid_len;
        else
                hdr->dout_resid = req->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 && req->result < 0)
                ret = req->result;

        blk_rq_unmap_user(bio);
        scsi_req_free_cmd(req);
        blk_put_request(rq);

        return ret;
}

static bool bsg_complete(struct bsg_device *bd)
{
        bool ret = false;
        bool spin;

        do {
                spin_lock_irq(&bd->lock);

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

                /*
                 * All commands consumed.
                 */
                if (bd->done_cmds == bd->queued_cmds)
                        ret = true;

                spin = !test_bit(BSG_F_BLOCK, &bd->flags);

                spin_unlock_irq(&bd->lock);
        } while (!ret && spin);

        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
         */
        io_wait_event(bd->wq_done, bsg_complete(bd));

        /*
         * 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 mode)
{
        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, mode);
                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);

        if (unlikely(uaccess_kernel()))
                return -EINVAL;

        bsg_set_block(bd, file);

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

        *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_queue_scsi_passthrough(rq)) {
                WARN_ONCE(true, "Attempt to register a non-SCSI queue\n");
                return ERR_PTR(-EINVAL);
        }

        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;

        mutex_lock(&bsg_mutex);

        hlist_for_each_entry(bd, 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;

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

                rq = bsg_map_hdr(bd, &hdr, file->f_mode);
                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;
        }
        default:
                return -ENOTTY;
        }
}

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;
        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 (!queue_is_rq_based(q))
                return 0;

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

        mutex_lock(&bsg_mutex);

        ret = idr_alloc(&bsg_minor_idr, bcd, 0, BSG_MAX_DEVS, GFP_KERNEL);
        if (ret < 0) {
                if (ret == -ENOSPC) {
                        printk(KERN_ERR "bsg: too many bsg devices\n");
                        ret = -EINVAL;
                }
                goto unlock;
        }

        bcd->minor = ret;
        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);
        idr_remove(&bsg_minor_idr, bcd->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);