/*
 * Copyright (C) 2000 Jens Axboe <axboe@suse.de>
 * Copyright (C) 2001-2004 Peter Osterlund <petero2@telia.com>
 * Copyright (C) 2006 Thomas Maier <balagi@justmail.de>
 *
 * May be copied or modified under the terms of the GNU General Public
 * License.  See linux/COPYING for more information.
 *
 * Packet writing layer for ATAPI and SCSI CD-RW, DVD+RW, DVD-RW and
 * DVD-RAM devices.
 *
 * Theory of operation:
 *
 * At the lowest level, there is the standard driver for the CD/DVD device,
 * typically ide-cd.c or sr.c. This driver can handle read and write requests,
 * but it doesn't know anything about the special restrictions that apply to
 * packet writing. One restriction is that write requests must be aligned to
 * packet boundaries on the physical media, and the size of a write request
 * must be equal to the packet size. Another restriction is that a
 * GPCMD_FLUSH_CACHE command has to be issued to the drive before a read
 * command, if the previous command was a write.
 *
 * The purpose of the packet writing driver is to hide these restrictions from
 * higher layers, such as file systems, and present a block device that can be
 * randomly read and written using 2kB-sized blocks.
 *
 * The lowest layer in the packet writing driver is the packet I/O scheduler.
 * Its data is defined by the struct packet_iosched and includes two bio
 * queues with pending read and write requests. These queues are processed
 * by the pkt_iosched_process_queue() function. The write requests in this
 * queue are already properly aligned and sized. This layer is responsible for
 * issuing the flush cache commands and scheduling the I/O in a good order.
 *
 * The next layer transforms unaligned write requests to aligned writes. This
 * transformation requires reading missing pieces of data from the underlying
 * block device, assembling the pieces to full packets and queuing them to the
 * packet I/O scheduler.
 *
 * At the top layer there is a custom ->submit_bio function that forwards
 * read requests directly to the iosched queue and puts write requests in the
 * unaligned write queue. A kernel thread performs the necessary read
 * gathering to convert the unaligned writes to aligned writes and then feeds
 * them to the packet I/O scheduler.
 *
 *************************************************************************/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/pktcdvd.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/compat.h>
#include <linux/kthread.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/miscdevice.h>
#include <linux/freezer.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi.h>
#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/nospec.h>
#include <linux/uaccess.h>

#define DRIVER_NAME     "pktcdvd"

#define pkt_err(pd, fmt, ...)                                           \
        pr_err("%s: " fmt, pd->name, ##__VA_ARGS__)
#define pkt_notice(pd, fmt, ...)                                        \
        pr_notice("%s: " fmt, pd->name, ##__VA_ARGS__)
#define pkt_info(pd, fmt, ...)                                          \
        pr_info("%s: " fmt, pd->name, ##__VA_ARGS__)

#define pkt_dbg(level, pd, fmt, ...)                                    \
do {                                                                    \
        if (level == 2 && PACKET_DEBUG >= 2)                            \
                pr_notice("%s: %s():" fmt,                              \
                          pd->name, __func__, ##__VA_ARGS__);           \
        else if (level == 1 && PACKET_DEBUG >= 1)                       \
                pr_notice("%s: " fmt, pd->name, ##__VA_ARGS__);         \
} while (0)

#define MAX_SPEED 0xffff

static DEFINE_MUTEX(pktcdvd_mutex);
static struct pktcdvd_device *pkt_devs[MAX_WRITERS];
static struct proc_dir_entry *pkt_proc;
static int pktdev_major;
static int write_congestion_on  = PKT_WRITE_CONGESTION_ON;
static int write_congestion_off = PKT_WRITE_CONGESTION_OFF;
static struct mutex ctl_mutex;  /* Serialize open/close/setup/teardown */
static mempool_t psd_pool;
static struct bio_set pkt_bio_set;

static struct class     *class_pktcdvd = NULL;    /* /sys/class/pktcdvd */
static struct dentry    *pkt_debugfs_root = NULL; /* /sys/kernel/debug/pktcdvd */

/* forward declaration */
static int pkt_setup_dev(dev_t dev, dev_t* pkt_dev);
static int pkt_remove_dev(dev_t pkt_dev);
static int pkt_seq_show(struct seq_file *m, void *p);

static sector_t get_zone(sector_t sector, struct pktcdvd_device *pd)
{
        return (sector + pd->offset) & ~(sector_t)(pd->settings.size - 1);
}

/*
 * create and register a pktcdvd kernel object.
 */
static struct pktcdvd_kobj* pkt_kobj_create(struct pktcdvd_device *pd,
                                        const char* name,
                                        struct kobject* parent,
                                        struct kobj_type* ktype)
{
        struct pktcdvd_kobj *p;
        int error;

        p = kzalloc(sizeof(*p), GFP_KERNEL);
        if (!p)
                return NULL;
        p->pd = pd;
        error = kobject_init_and_add(&p->kobj, ktype, parent, "%s", name);
        if (error) {
                kobject_put(&p->kobj);
                return NULL;
        }
        kobject_uevent(&p->kobj, KOBJ_ADD);
        return p;
}
/*
 * remove a pktcdvd kernel object.
 */
static void pkt_kobj_remove(struct pktcdvd_kobj *p)
{
        if (p)
                kobject_put(&p->kobj);
}
/*
 * default release function for pktcdvd kernel objects.
 */
static void pkt_kobj_release(struct kobject *kobj)
{
        kfree(to_pktcdvdkobj(kobj));
}


/**********************************************************
 *
 * sysfs interface for pktcdvd
 * by (C) 2006  Thomas Maier <balagi@justmail.de>
 *
 **********************************************************/

#define DEF_ATTR(_obj,_name,_mode) \
        static struct attribute _obj = { .name = _name, .mode = _mode }

/**********************************************************
  /sys/class/pktcdvd/pktcdvd[0-7]/
                     stat/reset
                     stat/packets_started
                     stat/packets_finished
                     stat/kb_written
                     stat/kb_read
                     stat/kb_read_gather
                     write_queue/size
                     write_queue/congestion_off
                     write_queue/congestion_on
 **********************************************************/

DEF_ATTR(kobj_pkt_attr_st1, "reset", 0200);
DEF_ATTR(kobj_pkt_attr_st2, "packets_started", 0444);
DEF_ATTR(kobj_pkt_attr_st3, "packets_finished", 0444);
DEF_ATTR(kobj_pkt_attr_st4, "kb_written", 0444);
DEF_ATTR(kobj_pkt_attr_st5, "kb_read", 0444);
DEF_ATTR(kobj_pkt_attr_st6, "kb_read_gather", 0444);

static struct attribute *kobj_pkt_attrs_stat[] = {
        &kobj_pkt_attr_st1,
        &kobj_pkt_attr_st2,
        &kobj_pkt_attr_st3,
        &kobj_pkt_attr_st4,
        &kobj_pkt_attr_st5,
        &kobj_pkt_attr_st6,
        NULL
};

DEF_ATTR(kobj_pkt_attr_wq1, "size", 0444);
DEF_ATTR(kobj_pkt_attr_wq2, "congestion_off", 0644);
DEF_ATTR(kobj_pkt_attr_wq3, "congestion_on",  0644);

static struct attribute *kobj_pkt_attrs_wqueue[] = {
        &kobj_pkt_attr_wq1,
        &kobj_pkt_attr_wq2,
        &kobj_pkt_attr_wq3,
        NULL
};

static ssize_t kobj_pkt_show(struct kobject *kobj,
                        struct attribute *attr, char *data)
{
        struct pktcdvd_device *pd = to_pktcdvdkobj(kobj)->pd;
        int n = 0;
        int v;
        if (strcmp(attr->name, "packets_started") == 0) {
                n = sprintf(data, "%lu\n", pd->stats.pkt_started);

        } else if (strcmp(attr->name, "packets_finished") == 0) {
                n = sprintf(data, "%lu\n", pd->stats.pkt_ended);

        } else if (strcmp(attr->name, "kb_written") == 0) {
                n = sprintf(data, "%lu\n", pd->stats.secs_w >> 1);

        } else if (strcmp(attr->name, "kb_read") == 0) {
                n = sprintf(data, "%lu\n", pd->stats.secs_r >> 1);

        } else if (strcmp(attr->name, "kb_read_gather") == 0) {
                n = sprintf(data, "%lu\n", pd->stats.secs_rg >> 1);

        } else if (strcmp(attr->name, "size") == 0) {
                spin_lock(&pd->lock);
                v = pd->bio_queue_size;
                spin_unlock(&pd->lock);
                n = sprintf(data, "%d\n", v);

        } else if (strcmp(attr->name, "congestion_off") == 0) {
                spin_lock(&pd->lock);
                v = pd->write_congestion_off;
                spin_unlock(&pd->lock);
                n = sprintf(data, "%d\n", v);

        } else if (strcmp(attr->name, "congestion_on") == 0) {
                spin_lock(&pd->lock);
                v = pd->write_congestion_on;
                spin_unlock(&pd->lock);
                n = sprintf(data, "%d\n", v);
        }
        return n;
}

static void init_write_congestion_marks(int* lo, int* hi)
{
        if (*hi > 0) {
                *hi = max(*hi, 500);
                *hi = min(*hi, 1000000);
                if (*lo <= 0)
                        *lo = *hi - 100;
                else {
                        *lo = min(*lo, *hi - 100);
                        *lo = max(*lo, 100);
                }
        } else {
                *hi = -1;
                *lo = -1;
        }
}

static ssize_t kobj_pkt_store(struct kobject *kobj,
                        struct attribute *attr,
                        const char *data, size_t len)
{
        struct pktcdvd_device *pd = to_pktcdvdkobj(kobj)->pd;
        int val;

        if (strcmp(attr->name, "reset") == 0 && len > 0) {
                pd->stats.pkt_started = 0;
                pd->stats.pkt_ended = 0;
                pd->stats.secs_w = 0;
                pd->stats.secs_rg = 0;
                pd->stats.secs_r = 0;

        } else if (strcmp(attr->name, "congestion_off") == 0
                   && sscanf(data, "%d", &val) == 1) {
                spin_lock(&pd->lock);
                pd->write_congestion_off = val;
                init_write_congestion_marks(&pd->write_congestion_off,
                                        &pd->write_congestion_on);
                spin_unlock(&pd->lock);

        } else if (strcmp(attr->name, "congestion_on") == 0
                   && sscanf(data, "%d", &val) == 1) {
                spin_lock(&pd->lock);
                pd->write_congestion_on = val;
                init_write_congestion_marks(&pd->write_congestion_off,
                                        &pd->write_congestion_on);
                spin_unlock(&pd->lock);
        }
        return len;
}

static const struct sysfs_ops kobj_pkt_ops = {
        .show = kobj_pkt_show,
        .store = kobj_pkt_store
};
static struct kobj_type kobj_pkt_type_stat = {
        .release = pkt_kobj_release,
        .sysfs_ops = &kobj_pkt_ops,
        .default_attrs = kobj_pkt_attrs_stat
};
static struct kobj_type kobj_pkt_type_wqueue = {
        .release = pkt_kobj_release,
        .sysfs_ops = &kobj_pkt_ops,
        .default_attrs = kobj_pkt_attrs_wqueue
};

static void pkt_sysfs_dev_new(struct pktcdvd_device *pd)
{
        if (class_pktcdvd) {
                pd->dev = device_create(class_pktcdvd, NULL, MKDEV(0, 0), NULL,
                                        "%s", pd->name);
                if (IS_ERR(pd->dev))
                        pd->dev = NULL;
        }
        if (pd->dev) {
                pd->kobj_stat = pkt_kobj_create(pd, "stat",
                                        &pd->dev->kobj,
                                        &kobj_pkt_type_stat);
                pd->kobj_wqueue = pkt_kobj_create(pd, "write_queue",
                                        &pd->dev->kobj,
                                        &kobj_pkt_type_wqueue);
        }
}

static void pkt_sysfs_dev_remove(struct pktcdvd_device *pd)
{
        pkt_kobj_remove(pd->kobj_stat);
        pkt_kobj_remove(pd->kobj_wqueue);
        if (class_pktcdvd)
                device_unregister(pd->dev);
}


/********************************************************************
  /sys/class/pktcdvd/
                     add            map block device
                     remove         unmap packet dev
                     device_map     show mappings
 *******************************************************************/

static void class_pktcdvd_release(struct class *cls)
{
        kfree(cls);
}

static ssize_t device_map_show(struct class *c, struct class_attribute *attr,
                               char *data)
{
        int n = 0;
        int idx;
        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
        for (idx = 0; idx < MAX_WRITERS; idx++) {
                struct pktcdvd_device *pd = pkt_devs[idx];
                if (!pd)
                        continue;
                n += sprintf(data+n, "%s %u:%u %u:%u\n",
                        pd->name,
                        MAJOR(pd->pkt_dev), MINOR(pd->pkt_dev),
                        MAJOR(pd->bdev->bd_dev),
                        MINOR(pd->bdev->bd_dev));
        }
        mutex_unlock(&ctl_mutex);
        return n;
}
static CLASS_ATTR_RO(device_map);

static ssize_t add_store(struct class *c, struct class_attribute *attr,
                         const char *buf, size_t count)
{
        unsigned int major, minor;

        if (sscanf(buf, "%u:%u", &major, &minor) == 2) {
                /* pkt_setup_dev() expects caller to hold reference to self */
                if (!try_module_get(THIS_MODULE))
                        return -ENODEV;

                pkt_setup_dev(MKDEV(major, minor), NULL);

                module_put(THIS_MODULE);

                return count;
        }

        return -EINVAL;
}
static CLASS_ATTR_WO(add);

static ssize_t remove_store(struct class *c, struct class_attribute *attr,
                            const char *buf, size_t count)
{
        unsigned int major, minor;
        if (sscanf(buf, "%u:%u", &major, &minor) == 2) {
                pkt_remove_dev(MKDEV(major, minor));
                return count;
        }
        return -EINVAL;
}
static CLASS_ATTR_WO(remove);

static struct attribute *class_pktcdvd_attrs[] = {
        &class_attr_add.attr,
        &class_attr_remove.attr,
        &class_attr_device_map.attr,
        NULL,
};
ATTRIBUTE_GROUPS(class_pktcdvd);

static int pkt_sysfs_init(void)
{
        int ret = 0;

        /*
         * create control files in sysfs
         * /sys/class/pktcdvd/...
         */
        class_pktcdvd = kzalloc(sizeof(*class_pktcdvd), GFP_KERNEL);
        if (!class_pktcdvd)
                return -ENOMEM;
        class_pktcdvd->name = DRIVER_NAME;
        class_pktcdvd->owner = THIS_MODULE;
        class_pktcdvd->class_release = class_pktcdvd_release;
        class_pktcdvd->class_groups = class_pktcdvd_groups;
        ret = class_register(class_pktcdvd);
        if (ret) {
                kfree(class_pktcdvd);
                class_pktcdvd = NULL;
                pr_err("failed to create class pktcdvd\n");
                return ret;
        }
        return 0;
}

static void pkt_sysfs_cleanup(void)
{
        if (class_pktcdvd)
                class_destroy(class_pktcdvd);
        class_pktcdvd = NULL;
}

/********************************************************************
  entries in debugfs

  /sys/kernel/debug/pktcdvd[0-7]/
                        info

 *******************************************************************/

static int pkt_debugfs_seq_show(struct seq_file *m, void *p)
{
        return pkt_seq_show(m, p);
}

static int pkt_debugfs_fops_open(struct inode *inode, struct file *file)
{
        return single_open(file, pkt_debugfs_seq_show, inode->i_private);
}

static const struct file_operations debug_fops = {
        .open           = pkt_debugfs_fops_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
        .owner          = THIS_MODULE,
};

static void pkt_debugfs_dev_new(struct pktcdvd_device *pd)
{
        if (!pkt_debugfs_root)
                return;
        pd->dfs_d_root = debugfs_create_dir(pd->name, pkt_debugfs_root);
        if (!pd->dfs_d_root)
                return;

        pd->dfs_f_info = debugfs_create_file("info", 0444,
                                             pd->dfs_d_root, pd, &debug_fops);
}

static void pkt_debugfs_dev_remove(struct pktcdvd_device *pd)
{
        if (!pkt_debugfs_root)
                return;
        debugfs_remove(pd->dfs_f_info);
        debugfs_remove(pd->dfs_d_root);
        pd->dfs_f_info = NULL;
        pd->dfs_d_root = NULL;
}

static void pkt_debugfs_init(void)
{
        pkt_debugfs_root = debugfs_create_dir(DRIVER_NAME, NULL);
}

static void pkt_debugfs_cleanup(void)
{
        debugfs_remove(pkt_debugfs_root);
        pkt_debugfs_root = NULL;
}

/* ----------------------------------------------------------*/


static void pkt_bio_finished(struct pktcdvd_device *pd)
{
        BUG_ON(atomic_read(&pd->cdrw.pending_bios) <= 0);
        if (atomic_dec_and_test(&pd->cdrw.pending_bios)) {
                pkt_dbg(2, pd, "queue empty\n");
                atomic_set(&pd->iosched.attention, 1);
                wake_up(&pd->wqueue);
        }
}

/*
 * Allocate a packet_data struct
 */
static struct packet_data *pkt_alloc_packet_data(int frames)
{
        int i;
        struct packet_data *pkt;

        pkt = kzalloc(sizeof(struct packet_data), GFP_KERNEL);
        if (!pkt)
                goto no_pkt;

        pkt->frames = frames;
        pkt->w_bio = bio_kmalloc(GFP_KERNEL, frames);
        if (!pkt->w_bio)
                goto no_bio;

        for (i = 0; i < frames / FRAMES_PER_PAGE; i++) {
                pkt->pages[i] = alloc_page(GFP_KERNEL|__GFP_ZERO);
                if (!pkt->pages[i])
                        goto no_page;
        }

        spin_lock_init(&pkt->lock);
        bio_list_init(&pkt->orig_bios);

        for (i = 0; i < frames; i++) {
                struct bio *bio = bio_kmalloc(GFP_KERNEL, 1);
                if (!bio)
                        goto no_rd_bio;

                pkt->r_bios[i] = bio;
        }

        return pkt;

no_rd_bio:
        for (i = 0; i < frames; i++) {
                struct bio *bio = pkt->r_bios[i];
                if (bio)
                        bio_put(bio);
        }

no_page:
        for (i = 0; i < frames / FRAMES_PER_PAGE; i++)
                if (pkt->pages[i])
                        __free_page(pkt->pages[i]);
        bio_put(pkt->w_bio);
no_bio:
        kfree(pkt);
no_pkt:
        return NULL;
}

/*
 * Free a packet_data struct
 */
static void pkt_free_packet_data(struct packet_data *pkt)
{
        int i;

        for (i = 0; i < pkt->frames; i++) {
                struct bio *bio = pkt->r_bios[i];
                if (bio)
                        bio_put(bio);
        }
        for (i = 0; i < pkt->frames / FRAMES_PER_PAGE; i++)
                __free_page(pkt->pages[i]);
        bio_put(pkt->w_bio);
        kfree(pkt);
}

static void pkt_shrink_pktlist(struct pktcdvd_device *pd)
{
        struct packet_data *pkt, *next;

        BUG_ON(!list_empty(&pd->cdrw.pkt_active_list));

        list_for_each_entry_safe(pkt, next, &pd->cdrw.pkt_free_list, list) {
                pkt_free_packet_data(pkt);
        }
        INIT_LIST_HEAD(&pd->cdrw.pkt_free_list);
}

static int pkt_grow_pktlist(struct pktcdvd_device *pd, int nr_packets)
{
        struct packet_data *pkt;

        BUG_ON(!list_empty(&pd->cdrw.pkt_free_list));

        while (nr_packets > 0) {
                pkt = pkt_alloc_packet_data(pd->settings.size >> 2);
                if (!pkt) {
                        pkt_shrink_pktlist(pd);
                        return 0;
                }
                pkt->id = nr_packets;
                pkt->pd = pd;
                list_add(&pkt->list, &pd->cdrw.pkt_free_list);
                nr_packets--;
        }
        return 1;
}

static inline struct pkt_rb_node *pkt_rbtree_next(struct pkt_rb_node *node)
{
        struct rb_node *n = rb_next(&node->rb_node);
        if (!n)
                return NULL;
        return rb_entry(n, struct pkt_rb_node, rb_node);
}

static void pkt_rbtree_erase(struct pktcdvd_device *pd, struct pkt_rb_node *node)
{
        rb_erase(&node->rb_node, &pd->bio_queue);
        mempool_free(node, &pd->rb_pool);
        pd->bio_queue_size--;
        BUG_ON(pd->bio_queue_size < 0);
}

/*
 * Find the first node in the pd->bio_queue rb tree with a starting sector >= s.
 */
static struct pkt_rb_node *pkt_rbtree_find(struct pktcdvd_device *pd, sector_t s)
{
        struct rb_node *n = pd->bio_queue.rb_node;
        struct rb_node *next;
        struct pkt_rb_node *tmp;

        if (!n) {
                BUG_ON(pd->bio_queue_size > 0);
                return NULL;
        }

        for (;;) {
                tmp = rb_entry(n, struct pkt_rb_node, rb_node);
                if (s <= tmp->bio->bi_iter.bi_sector)
                        next = n->rb_left;
                else
                        next = n->rb_right;
                if (!next)
                        break;
                n = next;
        }

        if (s > tmp->bio->bi_iter.bi_sector) {
                tmp = pkt_rbtree_next(tmp);
                if (!tmp)
                        return NULL;
        }
        BUG_ON(s > tmp->bio->bi_iter.bi_sector);
        return tmp;
}

/*
 * Insert a node into the pd->bio_queue rb tree.
 */
static void pkt_rbtree_insert(struct pktcdvd_device *pd, struct pkt_rb_node *node)
{
        struct rb_node **p = &pd->bio_queue.rb_node;
        struct rb_node *parent = NULL;
        sector_t s = node->bio->bi_iter.bi_sector;
        struct pkt_rb_node *tmp;

        while (*p) {
                parent = *p;
                tmp = rb_entry(parent, struct pkt_rb_node, rb_node);
                if (s < tmp->bio->bi_iter.bi_sector)
                        p = &(*p)->rb_left;
                else
                        p = &(*p)->rb_right;
        }
        rb_link_node(&node->rb_node, parent, p);
        rb_insert_color(&node->rb_node, &pd->bio_queue);
        pd->bio_queue_size++;
}

/*
 * Send a packet_command to the underlying block device and
 * wait for completion.
 */
static int pkt_generic_packet(struct pktcdvd_device *pd, struct packet_command *cgc)
{
        struct request_queue *q = bdev_get_queue(pd->bdev);
        struct request *rq;
        int ret = 0;

        rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ?
                             REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, 0);
        if (IS_ERR(rq))
                return PTR_ERR(rq);

        if (cgc->buflen) {
                ret = blk_rq_map_kern(q, rq, cgc->buffer, cgc->buflen,
                                      GFP_NOIO);
                if (ret)
                        goto out;
        }

        scsi_req(rq)->cmd_len = COMMAND_SIZE(cgc->cmd[0]);
        memcpy(scsi_req(rq)->cmd, cgc->cmd, CDROM_PACKET_SIZE);

        rq->timeout = 60*HZ;
        if (cgc->quiet)
                rq->rq_flags |= RQF_QUIET;

        blk_execute_rq(rq->q, pd->bdev->bd_disk, rq, 0);
        if (scsi_req(rq)->result)
                ret = -EIO;
out:
        blk_put_request(rq);
        return ret;
}

static const char *sense_key_string(__u8 index)
{
        static const char * const info[] = {
                "No sense", "Recovered error", "Not ready",
                "Medium error", "Hardware error", "Illegal request",
                "Unit attention", "Data protect", "Blank check",
        };

        return index < ARRAY_SIZE(info) ? info[index] : "INVALID";
}

/*
 * A generic sense dump / resolve mechanism should be implemented across
 * all ATAPI + SCSI devices.
 */
static void pkt_dump_sense(struct pktcdvd_device *pd,
                           struct packet_command *cgc)
{
        struct scsi_sense_hdr *sshdr = cgc->sshdr;

        if (sshdr)
                pkt_err(pd, "%*ph - sense %02x.%02x.%02x (%s)\n",
                        CDROM_PACKET_SIZE, cgc->cmd,
                        sshdr->sense_key, sshdr->asc, sshdr->ascq,
                        sense_key_string(sshdr->sense_key));
        else
                pkt_err(pd, "%*ph - no sense\n", CDROM_PACKET_SIZE, cgc->cmd);
}

/*
 * flush the drive cache to media
 */
static int pkt_flush_cache(struct pktcdvd_device *pd)
{
        struct packet_command cgc;

        init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
        cgc.cmd[0] = GPCMD_FLUSH_CACHE;
        cgc.quiet = 1;

        /*
         * the IMMED bit -- we default to not setting it, although that
         * would allow a much faster close, this is safer
         */
#if 0
        cgc.cmd[1] = 1 << 1;
#endif
        return pkt_generic_packet(pd, &cgc);
}

/*
 * speed is given as the normal factor, e.g. 4 for 4x
 */
static noinline_for_stack int pkt_set_speed(struct pktcdvd_device *pd,
                                unsigned write_speed, unsigned read_speed)
{
        struct packet_command cgc;
        struct scsi_sense_hdr sshdr;
        int ret;

        init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
        cgc.sshdr = &sshdr;
        cgc.cmd[0] = GPCMD_SET_SPEED;
        cgc.cmd[2] = (read_speed >> 8) & 0xff;
        cgc.cmd[3] = read_speed & 0xff;
        cgc.cmd[4] = (write_speed >> 8) & 0xff;
        cgc.cmd[5] = write_speed & 0xff;

        ret = pkt_generic_packet(pd, &cgc);
        if (ret)
                pkt_dump_sense(pd, &cgc);

        return ret;
}

/*
 * Queue a bio for processing by the low-level CD device. Must be called
 * from process context.
 */
static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio)
{
        spin_lock(&pd->iosched.lock);
        if (bio_data_dir(bio) == READ)
                bio_list_add(&pd->iosched.read_queue, bio);
        else
                bio_list_add(&pd->iosched.write_queue, bio);
        spin_unlock(&pd->iosched.lock);

        atomic_set(&pd->iosched.attention, 1);
        wake_up(&pd->wqueue);
}

/*
 * Process the queued read/write requests. This function handles special
 * requirements for CDRW drives:
 * - A cache flush command must be inserted before a read request if the
 *   previous request was a write.
 * - Switching between reading and writing is slow, so don't do it more often
 *   than necessary.
 * - Optimize for throughput at the expense of latency. This means that streaming
 *   writes will never be interrupted by a read, but if the drive has to seek
 *   before the next write, switch to reading instead if there are any pending
 *   read requests.
 * - Set the read speed according to current usage pattern. When only reading
 *   from the device, it's best to use the highest possible read speed, but
 *   when switching often between reading and writing, it's better to have the
 *   same read and write speeds.
 */
static void pkt_iosched_process_queue(struct pktcdvd_device *pd)
{

        if (atomic_read(&pd->iosched.attention) == 0)
                return;
        atomic_set(&pd->iosched.attention, 0);

        for (;;) {
                struct bio *bio;
                int reads_queued, writes_queued;

                spin_lock(&pd->iosched.lock);
                reads_queued = !bio_list_empty(&pd->iosched.read_queue);
                writes_queued = !bio_list_empty(&pd->iosched.write_queue);
                spin_unlock(&pd->iosched.lock);

                if (!reads_queued && !writes_queued)
                        break;

                if (pd->iosched.writing) {
                        int need_write_seek = 1;
                        spin_lock(&pd->iosched.lock);
                        bio = bio_list_peek(&pd->iosched.write_queue);
                        spin_unlock(&pd->iosched.lock);
                        if (bio && (bio->bi_iter.bi_sector ==
                                    pd->iosched.last_write))
                                need_write_seek = 0;
                        if (need_write_seek && reads_queued) {
                                if (atomic_read(&pd->cdrw.pending_bios) > 0) {
                                        pkt_dbg(2, pd, "write, waiting\n");
                                        break;
                                }
                                pkt_flush_cache(pd);
                                pd->iosched.writing = 0;
                        }
                } else {
                        if (!reads_queued && writes_queued) {
                                if (atomic_read(&pd->cdrw.pending_bios) > 0) {
                                        pkt_dbg(2, pd, "read, waiting\n");
                                        break;
                                }
                                pd->iosched.writing = 1;
                        }
                }

                spin_lock(&pd->iosched.lock);
                if (pd->iosched.writing)
                        bio = bio_list_pop(&pd->iosched.write_queue);
                else
                        bio = bio_list_pop(&pd->iosched.read_queue);
                spin_unlock(&pd->iosched.lock);

                if (!bio)
                        continue;

                if (bio_data_dir(bio) == READ)
                        pd->iosched.successive_reads +=
                                bio->bi_iter.bi_size >> 10;
                else {
                        pd->iosched.successive_reads = 0;
                        pd->iosched.last_write = bio_end_sector(bio);
                }
                if (pd->iosched.successive_reads >= HI_SPEED_SWITCH) {
                        if (pd->read_speed == pd->write_speed) {
                                pd->read_speed = MAX_SPEED;
                                pkt_set_speed(pd, pd->write_speed, pd->read_speed);
                        }
                } else {
                        if (pd->read_speed != pd->write_speed) {
                                pd->read_speed = pd->write_speed;
                                pkt_set_speed(pd, pd->write_speed, pd->read_speed);
                        }
                }

                atomic_inc(&pd->cdrw.pending_bios);
                submit_bio_noacct(bio);
        }
}

/*
 * Special care is needed if the underlying block device has a small
 * max_phys_segments value.
 */
static int pkt_set_segment_merging(struct pktcdvd_device *pd, struct request_queue *q)
{
        if ((pd->settings.size << 9) / CD_FRAMESIZE
            <= queue_max_segments(q)) {
                /*
                 * The cdrom device can handle one segment/frame
                 */
                clear_bit(PACKET_MERGE_SEGS, &pd->flags);
                return 0;
        } else if ((pd->settings.size << 9) / PAGE_SIZE
                   <= queue_max_segments(q)) {
                /*
                 * We can handle this case at the expense of some extra memory
                 * copies during write operations
                 */
                set_bit(PACKET_MERGE_SEGS, &pd->flags);
                return 0;
        } else {
                pkt_err(pd, "cdrom max_phys_segments too small\n");
                return -EIO;
        }
}

static void pkt_end_io_read(struct bio *bio)
{
        struct packet_data *pkt = bio->bi_private;
        struct pktcdvd_device *pd = pkt->pd;
        BUG_ON(!pd);

        pkt_dbg(2, pd, "bio=%p sec0=%llx sec=%llx err=%d\n",
                bio, (unsigned long long)pkt->sector,
                (unsigned long long)bio->bi_iter.bi_sector, bio->bi_status);

        if (bio->bi_status)
                atomic_inc(&pkt->io_errors);
        if (atomic_dec_and_test(&pkt->io_wait)) {
                atomic_inc(&pkt->run_sm);
                wake_up(&pd->wqueue);
        }
        pkt_bio_finished(pd);
}

static void pkt_end_io_packet_write(struct bio *bio)
{
        struct packet_data *pkt = bio->bi_private;
        struct pktcdvd_device *pd = pkt->pd;
        BUG_ON(!pd);

        pkt_dbg(2, pd, "id=%d, err=%d\n", pkt->id, bio->bi_status);

        pd->stats.pkt_ended++;

        pkt_bio_finished(pd);
        atomic_dec(&pkt->io_wait);
        atomic_inc(&pkt->run_sm);
        wake_up(&pd->wqueue);
}

/*
 * Schedule reads for the holes in a packet
 */
static void pkt_gather_data(struct pktcdvd_device *pd, struct packet_data *pkt)
{
        int frames_read = 0;
        struct bio *bio;
        int f;
        char written[PACKET_MAX_SIZE];

        BUG_ON(bio_list_empty(&pkt->orig_bios));

        atomic_set(&pkt->io_wait, 0);
        atomic_set(&pkt->io_errors, 0);

        /*
         * Figure out which frames we need to read before we can write.
         */
        memset(written, 0, sizeof(written));

        spin_lock(&pkt->lock);
        bio_list_for_each(bio, &pkt->orig_bios) {
                int first_frame = (bio->bi_iter.bi_sector - pkt->sector) /
                        (CD_FRAMESIZE >> 9);
                int num_frames = bio->bi_iter.bi_size / CD_FRAMESIZE;
                pd->stats.secs_w += num_frames * (CD_FRAMESIZE >> 9);
                BUG_ON(first_frame < 0);
                BUG_ON(first_frame + num_frames > pkt->frames);
                for (f = first_frame; f < first_frame + num_frames; f++)
                        written[f] = 1;
        }
        spin_unlock(&pkt->lock);

        if (pkt->cache_valid) {
                pkt_dbg(2, pd, "zone %llx cached\n",
                        (unsigned long long)pkt->sector);
                goto out_account;
        }

        /*
         * Schedule reads for missing parts of the packet.
         */
        for (f = 0; f < pkt->frames; f++) {
                int p, offset;

                if (written[f])
                        continue;

                bio = pkt->r_bios[f];
                bio_reset(bio);
                bio->bi_iter.bi_sector = pkt->sector + f * (CD_FRAMESIZE >> 9);
                bio_set_dev(bio, pd->bdev);
                bio->bi_end_io = pkt_end_io_read;
                bio->bi_private = pkt;

                p = (f * CD_FRAMESIZE) / PAGE_SIZE;
                offset = (f * CD_FRAMESIZE) % PAGE_SIZE;
                pkt_dbg(2, pd, "Adding frame %d, page:%p offs:%d\n",
                        f, pkt->pages[p], offset);
                if (!bio_add_page(bio, pkt->pages[p], CD_FRAMESIZE, offset))
                        BUG();

                atomic_inc(&pkt->io_wait);
                bio_set_op_attrs(bio, REQ_OP_READ, 0);
                pkt_queue_bio(pd, bio);
                frames_read++;
        }

out_account:
        pkt_dbg(2, pd, "need %d frames for zone %llx\n",
                frames_read, (unsigned long long)pkt->sector);
        pd->stats.pkt_started++;
        pd->stats.secs_rg += frames_read * (CD_FRAMESIZE >> 9);
}

/*
 * Find a packet matching zone, or the least recently used packet if
 * there is no match.
 */
static struct packet_data *pkt_get_packet_data(struct pktcdvd_device *pd, int zone)
{
        struct packet_data *pkt;

        list_for_each_entry(pkt, &pd->cdrw.pkt_free_list, list) {
                if (pkt->sector == zone || pkt->list.next == &pd->cdrw.pkt_free_list) {
                        list_del_init(&pkt->list);
                        if (pkt->sector != zone)
                                pkt->cache_valid = 0;
                        return pkt;
                }
        }
        BUG();
        return NULL;
}

static void pkt_put_packet_data(struct pktcdvd_device *pd, struct packet_data *pkt)
{
        if (pkt->cache_valid) {
                list_add(&pkt->list, &pd->cdrw.pkt_free_list);
        } else {
                list_add_tail(&pkt->list, &pd->cdrw.pkt_free_list);
        }
}

static inline void pkt_set_state(struct packet_data *pkt, enum packet_data_state state)
{
#if PACKET_DEBUG > 1
        static const char *state_name[] = {
                "IDLE", "WAITING", "READ_WAIT", "WRITE_WAIT", "RECOVERY", "FINISHED"
        };
        enum packet_data_state old_state = pkt->state;
        pkt_dbg(2, pd, "pkt %2d : s=%6llx %s -> %s\n",
                pkt->id, (unsigned long long)pkt->sector,
                state_name[old_state], state_name[state]);
#endif
        pkt->state = state;
}

/*
 * Scan the work queue to see if we can start a new packet.
 * returns non-zero if any work was done.
 */
static int pkt_handle_queue(struct pktcdvd_device *pd)
{
        struct packet_data *pkt, *p;
        struct bio *bio = NULL;
        sector_t zone = 0; /* Suppress gcc warning */
        struct pkt_rb_node *node, *first_node;
        struct rb_node *n;
        int wakeup;

        atomic_set(&pd->scan_queue, 0);

        if (list_empty(&pd->cdrw.pkt_free_list)) {
                pkt_dbg(2, pd, "no pkt\n");
                return 0;
        }

        /*
         * Try to find a zone we are not already working on.
         */
        spin_lock(&pd->lock);
        first_node = pkt_rbtree_find(pd, pd->current_sector);
        if (!first_node) {
                n = rb_first(&pd->bio_queue);
                if (n)
                        first_node = rb_entry(n, struct pkt_rb_node, rb_node);
        }
        node = first_node;
        while (node) {
                bio = node->bio;
                zone = get_zone(bio->bi_iter.bi_sector, pd);
                list_for_each_entry(p, &pd->cdrw.pkt_active_list, list) {
                        if (p->sector == zone) {
                                bio = NULL;
                                goto try_next_bio;
                        }
                }
                break;
try_next_bio:
                node = pkt_rbtree_next(node);
                if (!node) {
                        n = rb_first(&pd->bio_queue);
                        if (n)
                                node = rb_entry(n, struct pkt_rb_node, rb_node);
                }
                if (node == first_node)
                        node = NULL;
        }
        spin_unlock(&pd->lock);
        if (!bio) {
                pkt_dbg(2, pd, "no bio\n");
                return 0;
        }

        pkt = pkt_get_packet_data(pd, zone);

        pd->current_sector = zone + pd->settings.size;
        pkt->sector = zone;
        BUG_ON(pkt->frames != pd->settings.size >> 2);
        pkt->write_size = 0;

        /*
         * Scan work queue for bios in the same zone and link them
         * to this packet.
         */
        spin_lock(&pd->lock);
        pkt_dbg(2, pd, "looking for zone %llx\n", (unsigned long long)zone);
        while ((node = pkt_rbtree_find(pd, zone)) != NULL) {
                bio = node->bio;
                pkt_dbg(2, pd, "found zone=%llx\n", (unsigned long long)
                        get_zone(bio->bi_iter.bi_sector, pd));
                if (get_zone(bio->bi_iter.bi_sector, pd) != zone)
                        break;
                pkt_rbtree_erase(pd, node);
                spin_lock(&pkt->lock);
                bio_list_add(&pkt->orig_bios, bio);
                pkt->write_size += bio->bi_iter.bi_size / CD_FRAMESIZE;
                spin_unlock(&pkt->lock);
        }
        /* check write congestion marks, and if bio_queue_size is
           below, wake up any waiters */
        wakeup = (pd->write_congestion_on > 0
                        && pd->bio_queue_size <= pd->write_congestion_off);
        spin_unlock(&pd->lock);
        if (wakeup) {
                clear_bdi_congested(pd->disk->queue->backing_dev_info,
                                        BLK_RW_ASYNC);
        }

        pkt->sleep_time = max(PACKET_WAIT_TIME, 1);
        pkt_set_state(pkt, PACKET_WAITING_STATE);
        atomic_set(&pkt->run_sm, 1);

        spin_lock(&pd->cdrw.active_list_lock);
        list_add(&pkt->list, &pd->cdrw.pkt_active_list);
        spin_unlock(&pd->cdrw.active_list_lock);

        return 1;
}

/*
 * Assemble a bio to write one packet and queue the bio for processing
 * by the underlying block device.
 */
static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
{
        int f;

        bio_reset(pkt->w_bio);
        pkt->w_bio->bi_iter.bi_sector = pkt->sector;
        bio_set_dev(pkt->w_bio, pd->bdev);
        pkt->w_bio->bi_end_io = pkt_end_io_packet_write;
        pkt->w_bio->bi_private = pkt;

        /* XXX: locking? */
        for (f = 0; f < pkt->frames; f++) {
                struct page *page = pkt->pages[(f * CD_FRAMESIZE) / PAGE_SIZE];
                unsigned offset = (f * CD_FRAMESIZE) % PAGE_SIZE;

                if (!bio_add_page(pkt->w_bio, page, CD_FRAMESIZE, offset))
                        BUG();
        }
        pkt_dbg(2, pd, "vcnt=%d\n", pkt->w_bio->bi_vcnt);

        /*
         * Fill-in bvec with data from orig_bios.
         */
        spin_lock(&pkt->lock);
        bio_list_copy_data(pkt->w_bio, pkt->orig_bios.head);

        pkt_set_state(pkt, PACKET_WRITE_WAIT_STATE);
        spin_unlock(&pkt->lock);

        pkt_dbg(2, pd, "Writing %d frames for zone %llx\n",
                pkt->write_size, (unsigned long long)pkt->sector);

        if (test_bit(PACKET_MERGE_SEGS, &pd->flags) || (pkt->write_size < pkt->frames))
                pkt->cache_valid = 1;
        else
                pkt->cache_valid = 0;

        /* Start the write request */
        atomic_set(&pkt->io_wait, 1);
        bio_set_op_attrs(pkt->w_bio, REQ_OP_WRITE, 0);
        pkt_queue_bio(pd, pkt->w_bio);
}

static void pkt_finish_packet(struct packet_data *pkt, blk_status_t status)
{
        struct bio *bio;

        if (status)
                pkt->cache_valid = 0;

        /* Finish all bios corresponding to this packet */
        while ((bio = bio_list_pop(&pkt->orig_bios))) {
                bio->bi_status = status;
                bio_endio(bio);
        }
}

static void pkt_run_state_machine(struct pktcdvd_device *pd, struct packet_data *pkt)
{
        pkt_dbg(2, pd, "pkt %d\n", pkt->id);

        for (;;) {
                switch (pkt->state) {
                case PACKET_WAITING_STATE:
                        if ((pkt->write_size < pkt->frames) && (pkt->sleep_time > 0))
                                return;

                        pkt->sleep_time = 0;
                        pkt_gather_data(pd, pkt);
                        pkt_set_state(pkt, PACKET_READ_WAIT_STATE);
                        break;

                case PACKET_READ_WAIT_STATE:
                        if (atomic_read(&pkt->io_wait) > 0)
                                return;

                        if (atomic_read(&pkt->io_errors) > 0) {
                                pkt_set_state(pkt, PACKET_RECOVERY_STATE);
                        } else {
                                pkt_start_write(pd, pkt);
                        }
                        break;

                case PACKET_WRITE_WAIT_STATE:
                        if (atomic_read(&pkt->io_wait) > 0)
                                return;

                        if (!pkt->w_bio->bi_status) {
                                pkt_set_state(pkt, PACKET_FINISHED_STATE);
                        } else {
                                pkt_set_state(pkt, PACKET_RECOVERY_STATE);
                        }
                        break;

                case PACKET_RECOVERY_STATE:
                        pkt_dbg(2, pd, "No recovery possible\n");
                        pkt_set_state(pkt, PACKET_FINISHED_STATE);
                        break;

                case PACKET_FINISHED_STATE:
                        pkt_finish_packet(pkt, pkt->w_bio->bi_status);
                        return;

                default:
                        BUG();
                        break;
                }
        }
}

static void pkt_handle_packets(struct pktcdvd_device *pd)
{
        struct packet_data *pkt, *next;

        /*
         * Run state machine for active packets
         */
        list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
                if (atomic_read(&pkt->run_sm) > 0) {
                        atomic_set(&pkt->run_sm, 0);
                        pkt_run_state_machine(pd, pkt);
                }
        }

        /*
         * Move no longer active packets to the free list
         */
        spin_lock(&pd->cdrw.active_list_lock);
        list_for_each_entry_safe(pkt, next, &pd->cdrw.pkt_active_list, list) {
                if (pkt->state == PACKET_FINISHED_STATE) {
                        list_del(&pkt->list);
                        pkt_put_packet_data(pd, pkt);
                        pkt_set_state(pkt, PACKET_IDLE_STATE);
                        atomic_set(&pd->scan_queue, 1);
                }
        }
        spin_unlock(&pd->cdrw.active_list_lock);
}

static void pkt_count_states(struct pktcdvd_device *pd, int *states)
{
        struct packet_data *pkt;
        int i;

        for (i = 0; i < PACKET_NUM_STATES; i++)
                states[i] = 0;

        spin_lock(&pd->cdrw.active_list_lock);
        list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
                states[pkt->state]++;
        }
        spin_unlock(&pd->cdrw.active_list_lock);
}

/*
 * kcdrwd is woken up when writes have been queued for one of our
 * registered devices
 */
static int kcdrwd(void *foobar)
{
        struct pktcdvd_device *pd = foobar;
        struct packet_data *pkt;
        long min_sleep_time, residue;

        set_user_nice(current, MIN_NICE);
        set_freezable();

        for (;;) {
                DECLARE_WAITQUEUE(wait, current);

                /*
                 * Wait until there is something to do
                 */
                add_wait_queue(&pd->wqueue, &wait);
                for (;;) {
                        set_current_state(TASK_INTERRUPTIBLE);

                        /* Check if we need to run pkt_handle_queue */
                        if (atomic_read(&pd->scan_queue) > 0)
                                goto work_to_do;

                        /* Check if we need to run the state machine for some packet */
                        list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
                                if (atomic_read(&pkt->run_sm) > 0)
                                        goto work_to_do;
                        }

                        /* Check if we need to process the iosched queues */
                        if (atomic_read(&pd->iosched.attention) != 0)
                                goto work_to_do;

                        /* Otherwise, go to sleep */
                        if (PACKET_DEBUG > 1) {
                                int states[PACKET_NUM_STATES];
                                pkt_count_states(pd, states);
                                pkt_dbg(2, pd, "i:%d ow:%d rw:%d ww:%d rec:%d fin:%d\n",
                                        states[0], states[1], states[2],
                                        states[3], states[4], states[5]);
                        }

                        min_sleep_time = MAX_SCHEDULE_TIMEOUT;
                        list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
                                if (pkt->sleep_time && pkt->sleep_time < min_sleep_time)
                                        min_sleep_time = pkt->sleep_time;
                        }

                        pkt_dbg(2, pd, "sleeping\n");
                        residue = schedule_timeout(min_sleep_time);
                        pkt_dbg(2, pd, "wake up\n");

                        /* make swsusp happy with our thread */
                        try_to_freeze();

                        list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
                                if (!pkt->sleep_time)
                                        continue;
                                pkt->sleep_time -= min_sleep_time - residue;
                                if (pkt->sleep_time <= 0) {
                                        pkt->sleep_time = 0;
                                        atomic_inc(&pkt->run_sm);
                                }
                        }

                        if (kthread_should_stop())
                                break;
                }
work_to_do:
                set_current_state(TASK_RUNNING);
                remove_wait_queue(&pd->wqueue, &wait);

                if (kthread_should_stop())
                        break;

                /*
                 * if pkt_handle_queue returns true, we can queue
                 * another request.
                 */
                while (pkt_handle_queue(pd))
                        ;

                /*
                 * Handle packet state machine
                 */
                pkt_handle_packets(pd);

                /*
                 * Handle iosched queues
                 */
                pkt_iosched_process_queue(pd);
        }

        return 0;
}

static void pkt_print_settings(struct pktcdvd_device *pd)
{
        pkt_info(pd, "%s packets, %u blocks, Mode-%c disc\n",
                 pd->settings.fp ? "Fixed" : "Variable",
                 pd->settings.size >> 2,
                 pd->settings.block_mode == 8 ? '1' : '2');
}

static int pkt_mode_sense(struct pktcdvd_device *pd, struct packet_command *cgc, int page_code, int page_control)
{
        memset(cgc->cmd, 0, sizeof(cgc->cmd));

        cgc->cmd[0] = GPCMD_MODE_SENSE_10;
        cgc->cmd[2] = page_code | (page_control << 6);
        cgc->cmd[7] = cgc->buflen >> 8;
        cgc->cmd[8] = cgc->buflen & 0xff;
        cgc->data_direction = CGC_DATA_READ;
        return pkt_generic_packet(pd, cgc);
}

static int pkt_mode_select(struct pktcdvd_device *pd, struct packet_command *cgc)
{
        memset(cgc->cmd, 0, sizeof(cgc->cmd));
        memset(cgc->buffer, 0, 2);
        cgc->cmd[0] = GPCMD_MODE_SELECT_10;
        cgc->cmd[1] = 0x10;             /* PF */
        cgc->cmd[7] = cgc->buflen >> 8;
        cgc->cmd[8] = cgc->buflen & 0xff;
        cgc->data_direction = CGC_DATA_WRITE;
        return pkt_generic_packet(pd, cgc);
}

static int pkt_get_disc_info(struct pktcdvd_device *pd, disc_information *di)
{
        struct packet_command cgc;
        int ret;

        /* set up command and get the disc info */
        init_cdrom_command(&cgc, di, sizeof(*di), CGC_DATA_READ);
        cgc.cmd[0] = GPCMD_READ_DISC_INFO;
        cgc.cmd[8] = cgc.buflen = 2;
        cgc.quiet = 1;

        ret = pkt_generic_packet(pd, &cgc);
        if (ret)
                return ret;

        /* not all drives have the same disc_info length, so requeue
         * packet with the length the drive tells us it can supply
         */
        cgc.buflen = be16_to_cpu(di->disc_information_length) +
                     sizeof(di->disc_information_length);

        if (cgc.buflen > sizeof(disc_information))
                cgc.buflen = sizeof(disc_information);

        cgc.cmd[8] = cgc.buflen;
        return pkt_generic_packet(pd, &cgc);
}

static int pkt_get_track_info(struct pktcdvd_device *pd, __u16 track, __u8 type, track_information *ti)
{
        struct packet_command cgc;
        int ret;

        init_cdrom_command(&cgc, ti, 8, CGC_DATA_READ);
        cgc.cmd[0] = GPCMD_READ_TRACK_RZONE_INFO;
        cgc.cmd[1] = type & 3;
        cgc.cmd[4] = (track & 0xff00) >> 8;
        cgc.cmd[5] = track & 0xff;
        cgc.cmd[8] = 8;
        cgc.quiet = 1;

        ret = pkt_generic_packet(pd, &cgc);
        if (ret)
                return ret;

        cgc.buflen = be16_to_cpu(ti->track_information_length) +
                     sizeof(ti->track_information_length);

        if (cgc.buflen > sizeof(track_information))
                cgc.buflen = sizeof(track_information);

        cgc.cmd[8] = cgc.buflen;
        return pkt_generic_packet(pd, &cgc);
}

static noinline_for_stack int pkt_get_last_written(struct pktcdvd_device *pd,
                                                long *last_written)
{
        disc_information di;
        track_information ti;
        __u32 last_track;
        int ret;

        ret = pkt_get_disc_info(pd, &di);
        if (ret)
                return ret;

        last_track = (di.last_track_msb << 8) | di.last_track_lsb;
        ret = pkt_get_track_info(pd, last_track, 1, &ti);
        if (ret)
                return ret;

        /* if this track is blank, try the previous. */
        if (ti.blank) {
                last_track--;
                ret = pkt_get_track_info(pd, last_track, 1, &ti);
                if (ret)
                        return ret;
        }

        /* if last recorded field is valid, return it. */
        if (ti.lra_v) {
                *last_written = be32_to_cpu(ti.last_rec_address);
        } else {
                /* make it up instead */
                *last_written = be32_to_cpu(ti.track_start) +
                                be32_to_cpu(ti.track_size);
                if (ti.free_blocks)
                        *last_written -= (be32_to_cpu(ti.free_blocks) + 7);
        }
        return 0;
}

/*
 * write mode select package based on pd->settings
 */
static noinline_for_stack int pkt_set_write_settings(struct pktcdvd_device *pd)
{
        struct packet_command cgc;
        struct scsi_sense_hdr sshdr;
        write_param_page *wp;
        char buffer[128];
        int ret, size;

        /* doesn't apply to DVD+RW or DVD-RAM */
        if ((pd->mmc3_profile == 0x1a) || (pd->mmc3_profile == 0x12))
                return 0;

        memset(buffer, 0, sizeof(buffer));
        init_cdrom_command(&cgc, buffer, sizeof(*wp), CGC_DATA_READ);
        cgc.sshdr = &sshdr;
        ret = pkt_mode_sense(pd, &cgc, GPMODE_WRITE_PARMS_PAGE, 0);
        if (ret) {
                pkt_dump_sense(pd, &cgc);
                return ret;
        }

        size = 2 + ((buffer[0] << 8) | (buffer[1] & 0xff));
        pd->mode_offset = (buffer[6] << 8) | (buffer[7] & 0xff);
        if (size > sizeof(buffer))
                size = sizeof(buffer);

        /*
         * now get it all
         */
        init_cdrom_command(&cgc, buffer, size, CGC_DATA_READ);
        cgc.sshdr = &sshdr;
        ret = pkt_mode_sense(pd, &cgc, GPMODE_WRITE_PARMS_PAGE, 0);
        if (ret) {
                pkt_dump_sense(pd, &cgc);
                return ret;
        }

        /*
         * write page is offset header + block descriptor length
         */
        wp = (write_param_page *) &buffer[sizeof(struct mode_page_header) + pd->mode_offset];

        wp->fp = pd->settings.fp;
        wp->track_mode = pd->settings.track_mode;
        wp->write_type = pd->settings.write_type;
        wp->data_block_type = pd->settings.block_mode;

        wp->multi_session = 0;

#ifdef PACKET_USE_LS
        wp->link_size = 7;
        wp->ls_v = 1;
#endif

        if (wp->data_block_type == PACKET_BLOCK_MODE1) {
                wp->session_format = 0;
                wp->subhdr2 = 0x20;
        } else if (wp->data_block_type == PACKET_BLOCK_MODE2) {
                wp->session_format = 0x20;
                wp->subhdr2 = 8;
#if 0
                wp->mcn[0] = 0x80;
                memcpy(&wp->mcn[1], PACKET_MCN, sizeof(wp->mcn) - 1);
#endif
        } else {
                /*
                 * paranoia
                 */
                pkt_err(pd, "write mode wrong %d\n", wp->data_block_type);
                return 1;
        }
        wp->packet_size = cpu_to_be32(pd->settings.size >> 2);

        cgc.buflen = cgc.cmd[8] = size;
        ret = pkt_mode_select(pd, &cgc);
        if (ret) {
                pkt_dump_sense(pd, &cgc);
                return ret;
        }

        pkt_print_settings(pd);
        return 0;
}

/*
 * 1 -- we can write to this track, 0 -- we can't
 */
static int pkt_writable_track(struct pktcdvd_device *pd, track_information *ti)
{
        switch (pd->mmc3_profile) {
                case 0x1a: /* DVD+RW */
                case 0x12: /* DVD-RAM */
                        /* The track is always writable on DVD+RW/DVD-RAM */
                        return 1;
                default:
                        break;
        }

        if (!ti->packet || !ti->fp)
                return 0;

        /*
         * "good" settings as per Mt Fuji.
         */
        if (ti->rt == 0 && ti->blank == 0)
                return 1;

        if (ti->rt == 0 && ti->blank == 1)
                return 1;

        if (ti->rt == 1 && ti->blank == 0)
                return 1;

        pkt_err(pd, "bad state %d-%d-%d\n", ti->rt, ti->blank, ti->packet);
        return 0;
}

/*
 * 1 -- we can write to this disc, 0 -- we can't
 */
static int pkt_writable_disc(struct pktcdvd_device *pd, disc_information *di)
{
        switch (pd->mmc3_profile) {
                case 0x0a: /* CD-RW */
                case 0xffff: /* MMC3 not supported */
                        break;
                case 0x1a: /* DVD+RW */
                case 0x13: /* DVD-RW */
                case 0x12: /* DVD-RAM */
                        return 1;
                default:
                        pkt_dbg(2, pd, "Wrong disc profile (%x)\n",
                                pd->mmc3_profile);
                        return 0;
        }

        /*
         * for disc type 0xff we should probably reserve a new track.
         * but i'm not sure, should we leave this to user apps? probably.
         */
        if (di->disc_type == 0xff) {
                pkt_notice(pd, "unknown disc - no track?\n");
                return 0;
        }

        if (di->disc_type != 0x20 && di->disc_type != 0) {
                pkt_err(pd, "wrong disc type (%x)\n", di->disc_type);
                return 0;
        }

        if (di->erasable == 0) {
                pkt_notice(pd, "disc not erasable\n");
                return 0;
        }

        if (di->border_status == PACKET_SESSION_RESERVED) {
                pkt_err(pd, "can't write to last track (reserved)\n");
                return 0;
        }

        return 1;
}

static noinline_for_stack int pkt_probe_settings(struct pktcdvd_device *pd)
{
        struct packet_command cgc;
        unsigned char buf[12];
        disc_information di;
        track_information ti;
        int ret, track;

        init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
        cgc.cmd[0] = GPCMD_GET_CONFIGURATION;
        cgc.cmd[8] = 8;
        ret = pkt_generic_packet(pd, &cgc);
        pd->mmc3_profile = ret ? 0xffff : buf[6] << 8 | buf[7];

        memset(&di, 0, sizeof(disc_information));
        memset(&ti, 0, sizeof(track_information));

        ret = pkt_get_disc_info(pd, &di);
        if (ret) {
                pkt_err(pd, "failed get_disc\n");
                return ret;
        }

        if (!pkt_writable_disc(pd, &di))
                return -EROFS;

        pd->type = di.erasable ? PACKET_CDRW : PACKET_CDR;

        track = 1; /* (di.last_track_msb << 8) | di.last_track_lsb; */
        ret = pkt_get_track_info(pd, track, 1, &ti);
        if (ret) {
                pkt_err(pd, "failed get_track\n");
                return ret;
        }

        if (!pkt_writable_track(pd, &ti)) {
                pkt_err(pd, "can't write to this track\n");
                return -EROFS;
        }

        /*
         * we keep packet size in 512 byte units, makes it easier to
         * deal with request calculations.
         */
        pd->settings.size = be32_to_cpu(ti.fixed_packet_size) << 2;
        if (pd->settings.size == 0) {
                pkt_notice(pd, "detected zero packet size!\n");
                return -ENXIO;
        }
        if (pd->settings.size > PACKET_MAX_SECTORS) {
                pkt_err(pd, "packet size is too big\n");
                return -EROFS;
        }
        pd->settings.fp = ti.fp;
        pd->offset = (be32_to_cpu(ti.track_start) << 2) & (pd->settings.size - 1);

        if (ti.nwa_v) {
                pd->nwa = be32_to_cpu(ti.next_writable);
                set_bit(PACKET_NWA_VALID, &pd->flags);
        }

        /*
         * in theory we could use lra on -RW media as well and just zero
         * blocks that haven't been written yet, but in practice that
         * is just a no-go. we'll use that for -R, naturally.
         */
        if (ti.lra_v) {
                pd->lra = be32_to_cpu(ti.last_rec_address);
                set_bit(PACKET_LRA_VALID, &pd->flags);
        } else {
                pd->lra = 0xffffffff;
                set_bit(PACKET_LRA_VALID, &pd->flags);
        }

        /*
         * fine for now
         */
        pd->settings.link_loss = 7;
        pd->settings.write_type = 0;    /* packet */
        pd->settings.track_mode = ti.track_mode;

        /*
         * mode1 or mode2 disc
         */
        switch (ti.data_mode) {
                case PACKET_MODE1:
                        pd->settings.block_mode = PACKET_BLOCK_MODE1;
                        break;
                case PACKET_MODE2:
                        pd->settings.block_mode = PACKET_BLOCK_MODE2;
                        break;
                default:
                        pkt_err(pd, "unknown data mode\n");
                        return -EROFS;
        }
        return 0;
}

/*
 * enable/disable write caching on drive
 */
static noinline_for_stack int pkt_write_caching(struct pktcdvd_device *pd,
                                                int set)
{
        struct packet_command cgc;
        struct scsi_sense_hdr sshdr;
        unsigned char buf[64];
        int ret;

        init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_READ);
        cgc.sshdr = &sshdr;
        cgc.buflen = pd->mode_offset + 12;

        /*
         * caching mode page might not be there, so quiet this command
         */
        cgc.quiet = 1;

        ret = pkt_mode_sense(pd, &cgc, GPMODE_WCACHING_PAGE, 0);
        if (ret)
                return ret;

        buf[pd->mode_offset + 10] |= (!!set << 2);

        cgc.buflen = cgc.cmd[8] = 2 + ((buf[0] << 8) | (buf[1] & 0xff));
        ret = pkt_mode_select(pd, &cgc);
        if (ret) {
                pkt_err(pd, "write caching control failed\n");
                pkt_dump_sense(pd, &cgc);
        } else if (!ret && set)
                pkt_notice(pd, "enabled write caching\n");
        return ret;
}

static int pkt_lock_door(struct pktcdvd_device *pd, int lockflag)
{
        struct packet_command cgc;

        init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
        cgc.cmd[0] = GPCMD_PREVENT_ALLOW_MEDIUM_REMOVAL;
        cgc.cmd[4] = lockflag ? 1 : 0;
        return pkt_generic_packet(pd, &cgc);
}

/*
 * Returns drive maximum write speed
 */
static noinline_for_stack int pkt_get_max_speed(struct pktcdvd_device *pd,
                                                unsigned *write_speed)
{
        struct packet_command cgc;
        struct scsi_sense_hdr sshdr;
        unsigned char buf[256+18];
        unsigned char *cap_buf;
        int ret, offset;

        cap_buf = &buf[sizeof(struct mode_page_header) + pd->mode_offset];
        init_cdrom_command(&cgc, buf, sizeof(buf), CGC_DATA_UNKNOWN);
        cgc.sshdr = &sshdr;

        ret = pkt_mode_sense(pd, &cgc, GPMODE_CAPABILITIES_PAGE, 0);
        if (ret) {
                cgc.buflen = pd->mode_offset + cap_buf[1] + 2 +
                             sizeof(struct mode_page_header);
                ret = pkt_mode_sense(pd, &cgc, GPMODE_CAPABILITIES_PAGE, 0);
                if (ret) {
                        pkt_dump_sense(pd, &cgc);
                        return ret;
                }
        }

        offset = 20;                        /* Obsoleted field, used by older drives */
        if (cap_buf[1] >= 28)
                offset = 28;                /* Current write speed selected */
        if (cap_buf[1] >= 30) {
                /* If the drive reports at least one "Logical Unit Write
                 * Speed Performance Descriptor Block", use the information
                 * in the first block. (contains the highest speed)
                 */
                int num_spdb = (cap_buf[30] << 8) + cap_buf[31];
                if (num_spdb > 0)
                        offset = 34;
        }

        *write_speed = (cap_buf[offset] << 8) | cap_buf[offset + 1];
        return 0;
}

/* These tables from cdrecord - I don't have orange book */
/* standard speed CD-RW (1-4x) */
static char clv_to_speed[16] = {
        /* 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 */
           0, 2, 4, 6, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
/* high speed CD-RW (-10x) */
static char hs_clv_to_speed[16] = {
        /* 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 */
           0, 2, 4, 6, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
/* ultra high speed CD-RW */
static char us_clv_to_speed[16] = {
        /* 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 */
           0, 2, 4, 8, 0, 0,16, 0,24,32,40,48, 0, 0, 0, 0
};

/*
 * reads the maximum media speed from ATIP
 */
static noinline_for_stack int pkt_media_speed(struct pktcdvd_device *pd,
                                                unsigned *speed)
{
        struct packet_command cgc;
        struct scsi_sense_hdr sshdr;
        unsigned char buf[64];
        unsigned int size, st, sp;
        int ret;

        init_cdrom_command(&cgc, buf, 2, CGC_DATA_READ);
        cgc.sshdr = &sshdr;
        cgc.cmd[0] = GPCMD_READ_TOC_PMA_ATIP;
        cgc.cmd[1] = 2;
        cgc.cmd[2] = 4; /* READ ATIP */
        cgc.cmd[8] = 2;
        ret = pkt_generic_packet(pd, &cgc);
        if (ret) {
                pkt_dump_sense(pd, &cgc);
                return ret;
        }
        size = ((unsigned int) buf[0]<<8) + buf[1] + 2;
        if (size > sizeof(buf))
                size = sizeof(buf);

        init_cdrom_command(&cgc, buf, size, CGC_DATA_READ);
        cgc.sshdr = &sshdr;
        cgc.cmd[0] = GPCMD_READ_TOC_PMA_ATIP;
        cgc.cmd[1] = 2;
        cgc.cmd[2] = 4;
        cgc.cmd[8] = size;
        ret = pkt_generic_packet(pd, &cgc);
        if (ret) {
                pkt_dump_sense(pd, &cgc);
                return ret;
        }

        if (!(buf[6] & 0x40)) {
                pkt_notice(pd, "disc type is not CD-RW\n");
                return 1;
        }
        if (!(buf[6] & 0x4)) {
                pkt_notice(pd, "A1 values on media are not valid, maybe not CDRW?\n");

                return 1;
        }

        st = (buf[6] >> 3) & 0x7; /* disc sub-type */

        sp = buf[16] & 0xf; /* max speed from ATIP A1 field */

        /* Info from cdrecord */
        switch (st) {
                case 0: /* standard speed */
                        *speed = clv_to_speed[sp];
                        break;
                case 1: /* high speed */
                        *speed = hs_clv_to_speed[sp];
                        break;
                case 2: /* ultra high speed */
                        *speed = us_clv_to_speed[sp];
                        break;
                default:
                        pkt_notice(pd, "unknown disc sub-type %d\n", st);
                        return 1;
        }
        if (*speed) {
                pkt_info(pd, "maximum media speed: %d\n", *speed);
                return 0;
        } else {
                pkt_notice(pd, "unknown speed %d for sub-type %d\n", sp, st);
                return 1;
        }
}

static noinline_for_stack int pkt_perform_opc(struct pktcdvd_device *pd)
{
        struct packet_command cgc;
        struct scsi_sense_hdr sshdr;
        int ret;

        pkt_dbg(2, pd, "Performing OPC\n");

        init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
        cgc.sshdr = &sshdr;
        cgc.timeout = 60*HZ;
        cgc.cmd[0] = GPCMD_SEND_OPC;
        cgc.cmd[1] = 1;
        ret = pkt_generic_packet(pd, &cgc);
        if (ret)
                pkt_dump_sense(pd, &cgc);
        return ret;
}

static int pkt_open_write(struct pktcdvd_device *pd)
{
        int ret;
        unsigned int write_speed, media_write_speed, read_speed;

        ret = pkt_probe_settings(pd);
        if (ret) {
                pkt_dbg(2, pd, "failed probe\n");
                return ret;
        }

        ret = pkt_set_write_settings(pd);
        if (ret) {
                pkt_dbg(1, pd, "failed saving write settings\n");
                return -EIO;
        }

        pkt_write_caching(pd, USE_WCACHING);

        ret = pkt_get_max_speed(pd, &write_speed);
        if (ret)
                write_speed = 16 * 177;
        switch (pd->mmc3_profile) {
                case 0x13: /* DVD-RW */
                case 0x1a: /* DVD+RW */
                case 0x12: /* DVD-RAM */
                        pkt_dbg(1, pd, "write speed %ukB/s\n", write_speed);
                        break;
                default:
                        ret = pkt_media_speed(pd, &media_write_speed);
                        if (ret)
                                media_write_speed = 16;
                        write_speed = min(write_speed, media_write_speed * 177);
                        pkt_dbg(1, pd, "write speed %ux\n", write_speed / 176);
                        break;
        }
        read_speed = write_speed;

        ret = pkt_set_speed(pd, write_speed, read_speed);
        if (ret) {
                pkt_dbg(1, pd, "couldn't set write speed\n");
                return -EIO;
        }
        pd->write_speed = write_speed;
        pd->read_speed = read_speed;

        ret = pkt_perform_opc(pd);
        if (ret) {
                pkt_dbg(1, pd, "Optimum Power Calibration failed\n");
        }

        return 0;
}

/*
 * called at open time.
 */
static int pkt_open_dev(struct pktcdvd_device *pd, fmode_t write)
{
        int ret;
        long lba;
        struct request_queue *q;
        struct block_device *bdev;

        /*
         * We need to re-open the cdrom device without O_NONBLOCK to be able
         * to read/write from/to it. It is already opened in O_NONBLOCK mode
         * so open should not fail.
         */
        bdev = blkdev_get_by_dev(pd->bdev->bd_dev, FMODE_READ | FMODE_EXCL, pd);
        if (IS_ERR(bdev)) {
                ret = PTR_ERR(bdev);
                goto out;
        }

        ret = pkt_get_last_written(pd, &lba);
        if (ret) {
                pkt_err(pd, "pkt_get_last_written failed\n");
                goto out_putdev;
        }

        set_capacity(pd->disk, lba << 2);
        set_capacity(pd->bdev->bd_disk, lba << 2);
        bd_set_nr_sectors(pd->bdev, lba << 2);

        q = bdev_get_queue(pd->bdev);
        if (write) {
                ret = pkt_open_write(pd);
                if (ret)
                        goto out_putdev;
                /*
                 * Some CDRW drives can not handle writes larger than one packet,
                 * even if the size is a multiple of the packet size.
                 */
                blk_queue_max_hw_sectors(q, pd->settings.size);
                set_bit(PACKET_WRITABLE, &pd->flags);
        } else {
                pkt_set_speed(pd, MAX_SPEED, MAX_SPEED);
                clear_bit(PACKET_WRITABLE, &pd->flags);
        }

        ret = pkt_set_segment_merging(pd, q);
        if (ret)
                goto out_putdev;

        if (write) {
                if (!pkt_grow_pktlist(pd, CONFIG_CDROM_PKTCDVD_BUFFERS)) {
                        pkt_err(pd, "not enough memory for buffers\n");
                        ret = -ENOMEM;
                        goto out_putdev;
                }
                pkt_info(pd, "%lukB available on disc\n", lba << 1);
        }

        return 0;

out_putdev:
        blkdev_put(bdev, FMODE_READ | FMODE_EXCL);
out:
        return ret;
}

/*
 * called when the device is closed. makes sure that the device flushes
 * the internal cache before we close.
 */
static void pkt_release_dev(struct pktcdvd_device *pd, int flush)
{
        if (flush && pkt_flush_cache(pd))
                pkt_dbg(1, pd, "not flushing cache\n");

        pkt_lock_door(pd, 0);

        pkt_set_speed(pd, MAX_SPEED, MAX_SPEED);
        blkdev_put(pd->bdev, FMODE_READ | FMODE_EXCL);

        pkt_shrink_pktlist(pd);
}

static struct pktcdvd_device *pkt_find_dev_from_minor(unsigned int dev_minor)
{
        if (dev_minor >= MAX_WRITERS)
                return NULL;

        dev_minor = array_index_nospec(dev_minor, MAX_WRITERS);
        return pkt_devs[dev_minor];
}

static int pkt_open(struct block_device *bdev, fmode_t mode)
{
        struct pktcdvd_device *pd = NULL;
        int ret;

        mutex_lock(&pktcdvd_mutex);
        mutex_lock(&ctl_mutex);
        pd = pkt_find_dev_from_minor(MINOR(bdev->bd_dev));
        if (!pd) {
                ret = -ENODEV;
                goto out;
        }
        BUG_ON(pd->refcnt < 0);

        pd->refcnt++;
        if (pd->refcnt > 1) {
                if ((mode & FMODE_WRITE) &&
                    !test_bit(PACKET_WRITABLE, &pd->flags)) {
                        ret = -EBUSY;
                        goto out_dec;
                }
        } else {
                ret = pkt_open_dev(pd, mode & FMODE_WRITE);
                if (ret)
                        goto out_dec;
                /*
                 * needed here as well, since ext2 (among others) may change
                 * the blocksize at mount time
                 */
                set_blocksize(bdev, CD_FRAMESIZE);
        }

        mutex_unlock(&ctl_mutex);
        mutex_unlock(&pktcdvd_mutex);
        return 0;

out_dec:
        pd->refcnt--;
out:
        mutex_unlock(&ctl_mutex);
        mutex_unlock(&pktcdvd_mutex);
        return ret;
}

static void pkt_close(struct gendisk *disk, fmode_t mode)
{
        struct pktcdvd_device *pd = disk->private_data;

        mutex_lock(&pktcdvd_mutex);
        mutex_lock(&ctl_mutex);
        pd->refcnt--;
        BUG_ON(pd->refcnt < 0);
        if (pd->refcnt == 0) {
                int flush = test_bit(PACKET_WRITABLE, &pd->flags);
                pkt_release_dev(pd, flush);
        }
        mutex_unlock(&ctl_mutex);
        mutex_unlock(&pktcdvd_mutex);
}


static void pkt_end_io_read_cloned(struct bio *bio)
{
        struct packet_stacked_data *psd = bio->bi_private;
        struct pktcdvd_device *pd = psd->pd;

        psd->bio->bi_status = bio->bi_status;
        bio_put(bio);
        bio_endio(psd->bio);
        mempool_free(psd, &psd_pool);
        pkt_bio_finished(pd);
}

static void pkt_make_request_read(struct pktcdvd_device *pd, struct bio *bio)
{
        struct bio *cloned_bio = bio_clone_fast(bio, GFP_NOIO, &pkt_bio_set);
        struct packet_stacked_data *psd = mempool_alloc(&psd_pool, GFP_NOIO);

        psd->pd = pd;
        psd->bio = bio;
        bio_set_dev(cloned_bio, pd->bdev);
        cloned_bio->bi_private = psd;
        cloned_bio->bi_end_io = pkt_end_io_read_cloned;
        pd->stats.secs_r += bio_sectors(bio);
        pkt_queue_bio(pd, cloned_bio);
}

static void pkt_make_request_write(struct request_queue *q, struct bio *bio)
{
        struct pktcdvd_device *pd = q->queuedata;
        sector_t zone;
        struct packet_data *pkt;
        int was_empty, blocked_bio;
        struct pkt_rb_node *node;

        zone = get_zone(bio->bi_iter.bi_sector, pd);

        /*
         * If we find a matching packet in state WAITING or READ_WAIT, we can
         * just append this bio to that packet.
         */
        spin_lock(&pd->cdrw.active_list_lock);
        blocked_bio = 0;
        list_for_each_entry(pkt, &pd->cdrw.pkt_active_list, list) {
                if (pkt->sector == zone) {
                        spin_lock(&pkt->lock);
                        if ((pkt->state == PACKET_WAITING_STATE) ||
                            (pkt->state == PACKET_READ_WAIT_STATE)) {
                                bio_list_add(&pkt->orig_bios, bio);
                                pkt->write_size +=
                                        bio->bi_iter.bi_size / CD_FRAMESIZE;
                                if ((pkt->write_size >= pkt->frames) &&
                                    (pkt->state == PACKET_WAITING_STATE)) {
                                        atomic_inc(&pkt->run_sm);
                                        wake_up(&pd->wqueue);
                                }
                                spin_unlock(&pkt->lock);
                                spin_unlock(&pd->cdrw.active_list_lock);
                                return;
                        } else {
                                blocked_bio = 1;
                        }
                        spin_unlock(&pkt->lock);
                }
        }
        spin_unlock(&pd->cdrw.active_list_lock);

        /*
         * Test if there is enough room left in the bio work queue
         * (queue size >= congestion on mark).
         * If not, wait till the work queue size is below the congestion off mark.
         */
        spin_lock(&pd->lock);
        if (pd->write_congestion_on > 0
            && pd->bio_queue_size >= pd->write_congestion_on) {
                set_bdi_congested(q->backing_dev_info, BLK_RW_ASYNC);
                do {
                        spin_unlock(&pd->lock);
                        congestion_wait(BLK_RW_ASYNC, HZ);
                        spin_lock(&pd->lock);
                } while(pd->bio_queue_size > pd->write_congestion_off);
        }
        spin_unlock(&pd->lock);

        /*
         * No matching packet found. Store the bio in the work queue.
         */
        node = mempool_alloc(&pd->rb_pool, GFP_NOIO);
        node->bio = bio;
        spin_lock(&pd->lock);
        BUG_ON(pd->bio_queue_size < 0);
        was_empty = (pd->bio_queue_size == 0);
        pkt_rbtree_insert(pd, node);
        spin_unlock(&pd->lock);

        /*
         * Wake up the worker thread.
         */
        atomic_set(&pd->scan_queue, 1);
        if (was_empty) {
                /* This wake_up is required for correct operation */
                wake_up(&pd->wqueue);
        } else if (!list_empty(&pd->cdrw.pkt_free_list) && !blocked_bio) {
                /*
                 * This wake up is not required for correct operation,
                 * but improves performance in some cases.
                 */
                wake_up(&pd->wqueue);
        }
}

static blk_qc_t pkt_submit_bio(struct bio *bio)
{
        struct pktcdvd_device *pd;
        char b[BDEVNAME_SIZE];
        struct bio *split;

        blk_queue_split(&bio);

        pd = bio->bi_disk->queue->queuedata;
        if (!pd) {
                pr_err("%s incorrect request queue\n", bio_devname(bio, b));
                goto end_io;
        }

        pkt_dbg(2, pd, "start = %6llx stop = %6llx\n",
                (unsigned long long)bio->bi_iter.bi_sector,
                (unsigned long long)bio_end_sector(bio));

        /*
         * Clone READ bios so we can have our own bi_end_io callback.
         */
        if (bio_data_dir(bio) == READ) {
                pkt_make_request_read(pd, bio);
                return BLK_QC_T_NONE;
        }

        if (!test_bit(PACKET_WRITABLE, &pd->flags)) {
                pkt_notice(pd, "WRITE for ro device (%llu)\n",
                           (unsigned long long)bio->bi_iter.bi_sector);
                goto end_io;
        }

        if (!bio->bi_iter.bi_size || (bio->bi_iter.bi_size % CD_FRAMESIZE)) {
                pkt_err(pd, "wrong bio size\n");
                goto end_io;
        }

        do {
                sector_t zone = get_zone(bio->bi_iter.bi_sector, pd);
                sector_t last_zone = get_zone(bio_end_sector(bio) - 1, pd);

                if (last_zone != zone) {
                        BUG_ON(last_zone != zone + pd->settings.size);

                        split = bio_split(bio, last_zone -
                                          bio->bi_iter.bi_sector,
                                          GFP_NOIO, &pkt_bio_set);
                        bio_chain(split, bio);
                } else {
                        split = bio;
                }

                pkt_make_request_write(bio->bi_disk->queue, split);
        } while (split != bio);

        return BLK_QC_T_NONE;
end_io:
        bio_io_error(bio);
        return BLK_QC_T_NONE;
}

static void pkt_init_queue(struct pktcdvd_device *pd)
{
        struct request_queue *q = pd->disk->queue;

        blk_queue_logical_block_size(q, CD_FRAMESIZE);
        blk_queue_max_hw_sectors(q, PACKET_MAX_SECTORS);
        q->queuedata = pd;
}

static int pkt_seq_show(struct seq_file *m, void *p)
{
        struct pktcdvd_device *pd = m->private;
        char *msg;
        char bdev_buf[BDEVNAME_SIZE];
        int states[PACKET_NUM_STATES];

        seq_printf(m, "Writer %s mapped to %s:\n", pd->name,
                   bdevname(pd->bdev, bdev_buf));

        seq_printf(m, "\nSettings:\n");
        seq_printf(m, "\tpacket size:\t\t%dkB\n", pd->settings.size / 2);

        if (pd->settings.write_type == 0)
                msg = "Packet";
        else
                msg = "Unknown";
        seq_printf(m, "\twrite type:\t\t%s\n", msg);

        seq_printf(m, "\tpacket type:\t\t%s\n", pd->settings.fp ? "Fixed" : "Variable");
        seq_printf(m, "\tlink loss:\t\t%d\n", pd->settings.link_loss);

        seq_printf(m, "\ttrack mode:\t\t%d\n", pd->settings.track_mode);

        if (pd->settings.block_mode == PACKET_BLOCK_MODE1)
                msg = "Mode 1";
        else if (pd->settings.block_mode == PACKET_BLOCK_MODE2)
                msg = "Mode 2";
        else
                msg = "Unknown";
        seq_printf(m, "\tblock mode:\t\t%s\n", msg);

        seq_printf(m, "\nStatistics:\n");
        seq_printf(m, "\tpackets started:\t%lu\n", pd->stats.pkt_started);
        seq_printf(m, "\tpackets ended:\t\t%lu\n", pd->stats.pkt_ended);
        seq_printf(m, "\twritten:\t\t%lukB\n", pd->stats.secs_w >> 1);
        seq_printf(m, "\tread gather:\t\t%lukB\n", pd->stats.secs_rg >> 1);
        seq_printf(m, "\tread:\t\t\t%lukB\n", pd->stats.secs_r >> 1);

        seq_printf(m, "\nMisc:\n");
        seq_printf(m, "\treference count:\t%d\n", pd->refcnt);
        seq_printf(m, "\tflags:\t\t\t0x%lx\n", pd->flags);
        seq_printf(m, "\tread speed:\t\t%ukB/s\n", pd->read_speed);
        seq_printf(m, "\twrite speed:\t\t%ukB/s\n", pd->write_speed);
        seq_printf(m, "\tstart offset:\t\t%lu\n", pd->offset);
        seq_printf(m, "\tmode page offset:\t%u\n", pd->mode_offset);

        seq_printf(m, "\nQueue state:\n");
        seq_printf(m, "\tbios queued:\t\t%d\n", pd->bio_queue_size);
        seq_printf(m, "\tbios pending:\t\t%d\n", atomic_read(&pd->cdrw.pending_bios));
        seq_printf(m, "\tcurrent sector:\t\t0x%llx\n", (unsigned long long)pd->current_sector);

        pkt_count_states(pd, states);
        seq_printf(m, "\tstate:\t\t\ti:%d ow:%d rw:%d ww:%d rec:%d fin:%d\n",
                   states[0], states[1], states[2], states[3], states[4], states[5]);

        seq_printf(m, "\twrite congestion marks:\toff=%d on=%d\n",
                        pd->write_congestion_off,
                        pd->write_congestion_on);
        return 0;
}

static int pkt_new_dev(struct pktcdvd_device *pd, dev_t dev)
{
        int i;
        char b[BDEVNAME_SIZE];
        struct block_device *bdev;

        if (pd->pkt_dev == dev) {
                pkt_err(pd, "recursive setup not allowed\n");
                return -EBUSY;
        }
        for (i = 0; i < MAX_WRITERS; i++) {
                struct pktcdvd_device *pd2 = pkt_devs[i];
                if (!pd2)
                        continue;
                if (pd2->bdev->bd_dev == dev) {
                        pkt_err(pd, "%s already setup\n",
                                bdevname(pd2->bdev, b));
                        return -EBUSY;
                }
                if (pd2->pkt_dev == dev) {
                        pkt_err(pd, "can't chain pktcdvd devices\n");
                        return -EBUSY;
                }
        }

        bdev = blkdev_get_by_dev(dev, FMODE_READ | FMODE_NDELAY, NULL);
        if (IS_ERR(bdev))
                return PTR_ERR(bdev);
        if (!blk_queue_scsi_passthrough(bdev_get_queue(bdev))) {
                blkdev_put(bdev, FMODE_READ | FMODE_NDELAY);
                return -EINVAL;
        }

        /* This is safe, since we have a reference from open(). */
        __module_get(THIS_MODULE);

        pd->bdev = bdev;
        set_blocksize(bdev, CD_FRAMESIZE);

        pkt_init_queue(pd);

        atomic_set(&pd->cdrw.pending_bios, 0);
        pd->cdrw.thread = kthread_run(kcdrwd, pd, "%s", pd->name);
        if (IS_ERR(pd->cdrw.thread)) {
                pkt_err(pd, "can't start kernel thread\n");
                goto out_mem;
        }

        proc_create_single_data(pd->name, 0, pkt_proc, pkt_seq_show, pd);
        pkt_dbg(1, pd, "writer mapped to %s\n", bdevname(bdev, b));
        return 0;

out_mem:
        blkdev_put(bdev, FMODE_READ | FMODE_NDELAY);
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
        return -ENOMEM;
}

static int pkt_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd, unsigned long arg)
{
        struct pktcdvd_device *pd = bdev->bd_disk->private_data;
        int ret;

        pkt_dbg(2, pd, "cmd %x, dev %d:%d\n",
                cmd, MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));

        mutex_lock(&pktcdvd_mutex);
        switch (cmd) {
        case CDROMEJECT:
                /*
                 * The door gets locked when the device is opened, so we
                 * have to unlock it or else the eject command fails.
                 */
                if (pd->refcnt == 1)
                        pkt_lock_door(pd, 0);
                fallthrough;
        /*
         * forward selected CDROM ioctls to CD-ROM, for UDF
         */
        case CDROMMULTISESSION:
        case CDROMREADTOCENTRY:
        case CDROM_LAST_WRITTEN:
        case CDROM_SEND_PACKET:
        case SCSI_IOCTL_SEND_COMMAND:
                ret = __blkdev_driver_ioctl(pd->bdev, mode, cmd, arg);
                break;

        default:
                pkt_dbg(2, pd, "Unknown ioctl (%x)\n", cmd);
                ret = -ENOTTY;
        }
        mutex_unlock(&pktcdvd_mutex);

        return ret;
}

static unsigned int pkt_check_events(struct gendisk *disk,
                                     unsigned int clearing)
{
        struct pktcdvd_device *pd = disk->private_data;
        struct gendisk *attached_disk;

        if (!pd)
                return 0;
        if (!pd->bdev)
                return 0;
        attached_disk = pd->bdev->bd_disk;
        if (!attached_disk || !attached_disk->fops->check_events)
                return 0;
        return attached_disk->fops->check_events(attached_disk, clearing);
}

static char *pkt_devnode(struct gendisk *disk, umode_t *mode)
{
        return kasprintf(GFP_KERNEL, "pktcdvd/%s", disk->disk_name);
}

static const struct block_device_operations pktcdvd_ops = {
        .owner =                THIS_MODULE,
        .submit_bio =           pkt_submit_bio,
        .open =                 pkt_open,
        .release =              pkt_close,
        .ioctl =                pkt_ioctl,
        .compat_ioctl =         blkdev_compat_ptr_ioctl,
        .check_events =         pkt_check_events,
        .devnode =              pkt_devnode,
};

/*
 * Set up mapping from pktcdvd device to CD-ROM device.
 */
static int pkt_setup_dev(dev_t dev, dev_t* pkt_dev)
{
        int idx;
        int ret = -ENOMEM;
        struct pktcdvd_device *pd;
        struct gendisk *disk;

        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);

        for (idx = 0; idx < MAX_WRITERS; idx++)
                if (!pkt_devs[idx])
                        break;
        if (idx == MAX_WRITERS) {
                pr_err("max %d writers supported\n", MAX_WRITERS);
                ret = -EBUSY;
                goto out_mutex;
        }

        pd = kzalloc(sizeof(struct pktcdvd_device), GFP_KERNEL);
        if (!pd)
                goto out_mutex;

        ret = mempool_init_kmalloc_pool(&pd->rb_pool, PKT_RB_POOL_SIZE,
                                        sizeof(struct pkt_rb_node));
        if (ret)
                goto out_mem;

        INIT_LIST_HEAD(&pd->cdrw.pkt_free_list);
        INIT_LIST_HEAD(&pd->cdrw.pkt_active_list);
        spin_lock_init(&pd->cdrw.active_list_lock);

        spin_lock_init(&pd->lock);
        spin_lock_init(&pd->iosched.lock);
        bio_list_init(&pd->iosched.read_queue);
        bio_list_init(&pd->iosched.write_queue);
        sprintf(pd->name, DRIVER_NAME"%d", idx);
        init_waitqueue_head(&pd->wqueue);
        pd->bio_queue = RB_ROOT;

        pd->write_congestion_on  = write_congestion_on;
        pd->write_congestion_off = write_congestion_off;

        ret = -ENOMEM;
        disk = alloc_disk(1);
        if (!disk)
                goto out_mem;
        pd->disk = disk;
        disk->major = pktdev_major;
        disk->first_minor = idx;
        disk->fops = &pktcdvd_ops;
        disk->flags = GENHD_FL_REMOVABLE;
        strcpy(disk->disk_name, pd->name);
        disk->private_data = pd;
        disk->queue = blk_alloc_queue(NUMA_NO_NODE);
        if (!disk->queue)
                goto out_mem2;

        pd->pkt_dev = MKDEV(pktdev_major, idx);
        ret = pkt_new_dev(pd, dev);
        if (ret)
                goto out_mem2;

        /* inherit events of the host device */
        disk->events = pd->bdev->bd_disk->events;

        add_disk(disk);

        pkt_sysfs_dev_new(pd);
        pkt_debugfs_dev_new(pd);

        pkt_devs[idx] = pd;
        if (pkt_dev)
                *pkt_dev = pd->pkt_dev;

        mutex_unlock(&ctl_mutex);
        return 0;

out_mem2:
        put_disk(disk);
out_mem:
        mempool_exit(&pd->rb_pool);
        kfree(pd);
out_mutex:
        mutex_unlock(&ctl_mutex);
        pr_err("setup of pktcdvd device failed\n");
        return ret;
}

/*
 * Tear down mapping from pktcdvd device to CD-ROM device.
 */
static int pkt_remove_dev(dev_t pkt_dev)
{
        struct pktcdvd_device *pd;
        int idx;
        int ret = 0;

        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);

        for (idx = 0; idx < MAX_WRITERS; idx++) {
                pd = pkt_devs[idx];
                if (pd && (pd->pkt_dev == pkt_dev))
                        break;
        }
        if (idx == MAX_WRITERS) {
                pr_debug("dev not setup\n");
                ret = -ENXIO;
                goto out;
        }

        if (pd->refcnt > 0) {
                ret = -EBUSY;
                goto out;
        }
        if (!IS_ERR(pd->cdrw.thread))
                kthread_stop(pd->cdrw.thread);

        pkt_devs[idx] = NULL;

        pkt_debugfs_dev_remove(pd);
        pkt_sysfs_dev_remove(pd);

        blkdev_put(pd->bdev, FMODE_READ | FMODE_NDELAY);

        remove_proc_entry(pd->name, pkt_proc);
        pkt_dbg(1, pd, "writer unmapped\n");

        del_gendisk(pd->disk);
        blk_cleanup_queue(pd->disk->queue);
        put_disk(pd->disk);

        mempool_exit(&pd->rb_pool);
        kfree(pd);

        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);

out:
        mutex_unlock(&ctl_mutex);
        return ret;
}

static void pkt_get_status(struct pkt_ctrl_command *ctrl_cmd)
{
        struct pktcdvd_device *pd;

        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);

        pd = pkt_find_dev_from_minor(ctrl_cmd->dev_index);
        if (pd) {
                ctrl_cmd->dev = new_encode_dev(pd->bdev->bd_dev);
                ctrl_cmd->pkt_dev = new_encode_dev(pd->pkt_dev);
        } else {
                ctrl_cmd->dev = 0;
                ctrl_cmd->pkt_dev = 0;
        }
        ctrl_cmd->num_devices = MAX_WRITERS;

        mutex_unlock(&ctl_mutex);
}

static long pkt_ctl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        struct pkt_ctrl_command ctrl_cmd;
        int ret = 0;
        dev_t pkt_dev = 0;

        if (cmd != PACKET_CTRL_CMD)
                return -ENOTTY;

        if (copy_from_user(&ctrl_cmd, argp, sizeof(struct pkt_ctrl_command)))
                return -EFAULT;

        switch (ctrl_cmd.command) {
        case PKT_CTRL_CMD_SETUP:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                ret = pkt_setup_dev(new_decode_dev(ctrl_cmd.dev), &pkt_dev);
                ctrl_cmd.pkt_dev = new_encode_dev(pkt_dev);
                break;
        case PKT_CTRL_CMD_TEARDOWN:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                ret = pkt_remove_dev(new_decode_dev(ctrl_cmd.pkt_dev));
                break;
        case PKT_CTRL_CMD_STATUS:
                pkt_get_status(&ctrl_cmd);
                break;
        default:
                return -ENOTTY;
        }

        if (copy_to_user(argp, &ctrl_cmd, sizeof(struct pkt_ctrl_command)))
                return -EFAULT;
        return ret;
}

#ifdef CONFIG_COMPAT
static long pkt_ctl_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        return pkt_ctl_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static const struct file_operations pkt_ctl_fops = {
        .open           = nonseekable_open,
        .unlocked_ioctl = pkt_ctl_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = pkt_ctl_compat_ioctl,
#endif
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
};

static struct miscdevice pkt_misc = {
        .minor          = MISC_DYNAMIC_MINOR,
        .name           = DRIVER_NAME,
        .nodename       = "pktcdvd/control",
        .fops           = &pkt_ctl_fops
};

static int __init pkt_init(void)
{
        int ret;

        mutex_init(&ctl_mutex);

        ret = mempool_init_kmalloc_pool(&psd_pool, PSD_POOL_SIZE,
                                    sizeof(struct packet_stacked_data));
        if (ret)
                return ret;
        ret = bioset_init(&pkt_bio_set, BIO_POOL_SIZE, 0, 0);
        if (ret) {
                mempool_exit(&psd_pool);
                return ret;
        }

        ret = register_blkdev(pktdev_major, DRIVER_NAME);
        if (ret < 0) {
                pr_err("unable to register block device\n");
                goto out2;
        }
        if (!pktdev_major)
                pktdev_major = ret;

        ret = pkt_sysfs_init();
        if (ret)
                goto out;

        pkt_debugfs_init();

        ret = misc_register(&pkt_misc);
        if (ret) {
                pr_err("unable to register misc device\n");
                goto out_misc;
        }

        pkt_proc = proc_mkdir("driver/"DRIVER_NAME, NULL);

        return 0;

out_misc:
        pkt_debugfs_cleanup();
        pkt_sysfs_cleanup();
out:
        unregister_blkdev(pktdev_major, DRIVER_NAME);
out2:
        mempool_exit(&psd_pool);
        bioset_exit(&pkt_bio_set);
        return ret;
}

static void __exit pkt_exit(void)
{
        remove_proc_entry("driver/"DRIVER_NAME, NULL);
        misc_deregister(&pkt_misc);

        pkt_debugfs_cleanup();
        pkt_sysfs_cleanup();

        unregister_blkdev(pktdev_major, DRIVER_NAME);
        mempool_exit(&psd_pool);
        bioset_exit(&pkt_bio_set);
}

MODULE_DESCRIPTION("Packet writing layer for CD/DVD drives");
MODULE_AUTHOR("Jens Axboe <axboe@suse.de>");
MODULE_LICENSE("GPL");

module_init(pkt_init);
module_exit(pkt_exit);