pktcdvd.c 76.4 KB
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/*
 * Copyright (C) 2000 Jens Axboe <axboe@suse.de>
 * Copyright (C) 2001-2004 Peter Osterlund <petero2@telia.com>
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 * Copyright (C) 2006 Thomas Maier <balagi@justmail.de>
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 *
 * May be copied or modified under the terms of the GNU General Public
 * License.  See linux/COPYING for more information.
 *
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 * Packet writing layer for ATAPI and SCSI CD-RW, DVD+RW, DVD-RW and
 * DVD-RAM devices.
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 *
 * Theory of operation:
 *
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 * 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 make_request_fn 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.
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 *
 *************************************************************************/

#include <linux/pktcdvd.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.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>
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#include <linux/freezer.h>
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#include <linux/mutex.h>
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#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_ioctl.h>
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#include <scsi/scsi.h>
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#include <linux/debugfs.h>
#include <linux/device.h>
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#include <asm/uaccess.h>

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#define DRIVER_NAME	"pktcdvd"

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#if PACKET_DEBUG
#define DPRINTK(fmt, args...) printk(KERN_NOTICE fmt, ##args)
#else
#define DPRINTK(fmt, args...)
#endif

#if PACKET_DEBUG > 1
#define VPRINTK(fmt, args...) printk(KERN_NOTICE fmt, ##args)
#else
#define VPRINTK(fmt, args...)
#endif

#define MAX_SPEED 0xffff

#define ZONE(sector, pd) (((sector) + (pd)->offset) & ~((pd)->settings.size - 1))

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

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



/*
 * 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;
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	int error;

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	p = kzalloc(sizeof(*p), GFP_KERNEL);
	if (!p)
		return NULL;
	p->pd = pd;
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	error = kobject_init_and_add(&p->kobj, ktype, parent, "%s", name);
	if (error) {
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		kobject_put(&p->kobj);
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		return NULL;
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	}
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	kobject_uevent(&p->kobj, KOBJ_ADD);
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	return p;
}
/*
 * remove a pktcdvd kernel object.
 */
static void pkt_kobj_remove(struct pktcdvd_kobj *p)
{
	if (p)
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		kobject_put(&p->kobj);
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}
/*
 * 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) \
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	static struct attribute _obj = { .name = _name, .mode = _mode }
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/**********************************************************
  /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;

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	if (strcmp(attr->name, "reset") == 0 && len > 0) {
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		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
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		   && sscanf(data, "%d", &val) == 1) {
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		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
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		   && sscanf(data, "%d", &val) == 1) {
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		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 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) {
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		pd->dev = device_create(class_pktcdvd, NULL, MKDEV(0, 0), NULL,
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					"%s", pd->name);
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		if (IS_ERR(pd->dev))
			pd->dev = NULL;
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	}
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	if (pd->dev) {
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		pd->kobj_stat = pkt_kobj_create(pd, "stat",
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					&pd->dev->kobj,
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					&kobj_pkt_type_stat);
		pd->kobj_wqueue = pkt_kobj_create(pd, "write_queue",
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					&pd->dev->kobj,
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					&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)
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		device_destroy(class_pktcdvd, pd->pkt_dev);
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}


/********************************************************************
  /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 class_pktcdvd_show_map(struct class *c, 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 ssize_t class_pktcdvd_store_add(struct class *c, const char *buf,
					size_t count)
{
	unsigned int major, minor;
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	if (sscanf(buf, "%u:%u", &major, &minor) == 2) {
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		/* pkt_setup_dev() expects caller to hold reference to self */
		if (!try_module_get(THIS_MODULE))
			return -ENODEV;

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

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		return count;
	}
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	return -EINVAL;
}

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

static struct class_attribute class_pktcdvd_attrs[] = {
 __ATTR(add,            0200, NULL, class_pktcdvd_store_add),
 __ATTR(remove,         0200, NULL, class_pktcdvd_store_remove),
 __ATTR(device_map,     0444, class_pktcdvd_show_map, NULL),
 __ATTR_NULL
};


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_attrs = class_pktcdvd_attrs;
	ret = class_register(class_pktcdvd);
	if (ret) {
		kfree(class_pktcdvd);
		class_pktcdvd = NULL;
		printk(DRIVER_NAME": 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

  /debugfs/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);
}

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static const struct file_operations debug_fops = {
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	.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_f_info = NULL;
	pd->dfs_d_root = debugfs_create_dir(pd->name, pkt_debugfs_root);
	if (IS_ERR(pd->dfs_d_root)) {
		pd->dfs_d_root = NULL;
		return;
	}
	pd->dfs_f_info = debugfs_create_file("info", S_IRUGO,
				pd->dfs_d_root, pd, &debug_fops);
	if (IS_ERR(pd->dfs_f_info)) {
		pd->dfs_f_info = NULL;
		return;
	}
}

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

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

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

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

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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)) {
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		VPRINTK(DRIVER_NAME": queue empty\n");
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		atomic_set(&pd->iosched.attention, 1);
		wake_up(&pd->wqueue);
	}
}

static void pkt_bio_destructor(struct bio *bio)
{
	kfree(bio->bi_io_vec);
	kfree(bio);
}

static struct bio *pkt_bio_alloc(int nr_iovecs)
{
	struct bio_vec *bvl = NULL;
	struct bio *bio;

	bio = kmalloc(sizeof(struct bio), GFP_KERNEL);
	if (!bio)
		goto no_bio;
	bio_init(bio);

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	bvl = kcalloc(nr_iovecs, sizeof(struct bio_vec), GFP_KERNEL);
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	if (!bvl)
		goto no_bvl;

	bio->bi_max_vecs = nr_iovecs;
	bio->bi_io_vec = bvl;
	bio->bi_destructor = pkt_bio_destructor;

	return bio;

 no_bvl:
	kfree(bio);
 no_bio:
	return NULL;
}

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

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

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	pkt->frames = frames;
	pkt->w_bio = pkt_bio_alloc(frames);
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	if (!pkt->w_bio)
		goto no_bio;

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

	spin_lock_init(&pkt->lock);

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	for (i = 0; i < frames; i++) {
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		struct bio *bio = pkt_bio_alloc(1);
		if (!bio)
			goto no_rd_bio;
		pkt->r_bios[i] = bio;
	}

	return pkt;

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

no_page:
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	for (i = 0; i < frames / FRAMES_PER_PAGE; i++)
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		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;

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	for (i = 0; i < pkt->frames; i++) {
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		struct bio *bio = pkt->r_bios[i];
		if (bio)
			bio_put(bio);
	}
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	for (i = 0; i < pkt->frames / FRAMES_PER_PAGE; i++)
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		__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);
	}
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	INIT_LIST_HEAD(&pd->cdrw.pkt_free_list);
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}

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

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

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	while (nr_packets > 0) {
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		pkt = pkt_alloc_packet_data(pd->settings.size >> 2);
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		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);
}

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static void pkt_rbtree_erase(struct pktcdvd_device *pd, struct pkt_rb_node *node)
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{
	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_sector)
			next = n->rb_left;
		else
			next = n->rb_right;
		if (!next)
			break;
		n = next;
	}

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

/*
 * Add a bio to a single linked list defined by its head and tail pointers.
 */
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static void pkt_add_list_last(struct bio *bio, struct bio **list_head, struct bio **list_tail)
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{
	bio->bi_next = NULL;
	if (*list_tail) {
		BUG_ON((*list_head) == NULL);
		(*list_tail)->bi_next = bio;
		(*list_tail) = bio;
	} else {
		BUG_ON((*list_head) != NULL);
		(*list_head) = bio;
		(*list_tail) = bio;
	}
}

/*
 * Remove and return the first bio from a single linked list defined by its
 * head and tail pointers.
 */
static inline struct bio *pkt_get_list_first(struct bio **list_head, struct bio **list_tail)
{
	struct bio *bio;

	if (*list_head == NULL)
		return NULL;

	bio = *list_head;
	*list_head = bio->bi_next;
	if (*list_head == NULL)
		*list_tail = NULL;

	bio->bi_next = NULL;
	return bio;
}

/*
 * 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)
{
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	struct request_queue *q = bdev_get_queue(pd->bdev);
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	struct request *rq;
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	int ret = 0;

	rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ?
			     WRITE : READ, __GFP_WAIT);

	if (cgc->buflen) {
		if (blk_rq_map_kern(q, rq, cgc->buffer, cgc->buflen, __GFP_WAIT))
			goto out;
	}
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	rq->cmd_len = COMMAND_SIZE(cgc->cmd[0]);
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	memcpy(rq->cmd, cgc->cmd, CDROM_PACKET_SIZE);
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	rq->timeout = 60*HZ;
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	rq->cmd_type = REQ_TYPE_BLOCK_PC;
	rq->cmd_flags |= REQ_HARDBARRIER;
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	if (cgc->quiet)
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		rq->cmd_flags |= REQ_QUIET;
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	blk_execute_rq(rq->q, pd->bdev->bd_disk, rq, 0);
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	if (rq->errors)
		ret = -EIO;
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out:
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	blk_put_request(rq);
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	return ret;
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}

/*
 * A generic sense dump / resolve mechanism should be implemented across
 * all ATAPI + SCSI devices.
 */
static void pkt_dump_sense(struct packet_command *cgc)
{
	static char *info[9] = { "No sense", "Recovered error", "Not ready",
				 "Medium error", "Hardware error", "Illegal request",
				 "Unit attention", "Data protect", "Blank check" };
	int i;
	struct request_sense *sense = cgc->sense;

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	printk(DRIVER_NAME":");
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	for (i = 0; i < CDROM_PACKET_SIZE; i++)
		printk(" %02x", cgc->cmd[i]);
	printk(" - ");

	if (sense == NULL) {
		printk("no sense\n");
		return;
	}

	printk("sense %02x.%02x.%02x", sense->sense_key, sense->asc, sense->ascq);

	if (sense->sense_key > 8) {
		printk(" (INVALID)\n");
		return;
	}

	printk(" (%s)\n", info[sense->sense_key]);
}

/*
 * 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
 */
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static noinline_for_stack int pkt_set_speed(struct pktcdvd_device *pd,
				unsigned write_speed, unsigned read_speed)
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{
	struct packet_command cgc;
	struct request_sense sense;
	int ret;

	init_cdrom_command(&cgc, NULL, 0, CGC_DATA_NONE);
	cgc.sense = &sense;
	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;

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

	return ret;
}

/*
 * Queue a bio for processing by the low-level CD device. Must be called
 * from process context.
 */
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static void pkt_queue_bio(struct pktcdvd_device *pd, struct bio *bio)
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{
	spin_lock(&pd->iosched.lock);
	if (bio_data_dir(bio) == READ) {
		pkt_add_list_last(bio, &pd->iosched.read_queue,
				  &pd->iosched.read_queue_tail);
	} else {
		pkt_add_list_last(bio, &pd->iosched.write_queue,
				  &pd->iosched.write_queue_tail);
	}
	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.
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 * - Switching between reading and writing is slow, so don't do it more often
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 *   than necessary.
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 * - 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.
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 * - 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;
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		int reads_queued, writes_queued;
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		spin_lock(&pd->iosched.lock);
		reads_queued = (pd->iosched.read_queue != NULL);
		writes_queued = (pd->iosched.write_queue != NULL);
		spin_unlock(&pd->iosched.lock);

		if (!reads_queued && !writes_queued)
			break;

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

		spin_lock(&pd->iosched.lock);
		if (pd->iosched.writing) {
			bio = pkt_get_list_first(&pd->iosched.write_queue,
						 &pd->iosched.write_queue_tail);
		} else {
			bio = pkt_get_list_first(&pd->iosched.read_queue,
						 &pd->iosched.read_queue_tail);
		}
		spin_unlock(&pd->iosched.lock);

		if (!bio)
			continue;

		if (bio_data_dir(bio) == READ)
			pd->iosched.successive_reads += bio->bi_size >> 10;
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		else {
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			pd->iosched.successive_reads = 0;
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			pd->iosched.last_write = bio->bi_sector + bio_sectors(bio);
		}
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		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);
		generic_make_request(bio);
	}
}

/*
 * Special care is needed if the underlying block device has a small
 * max_phys_segments value.
 */
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static int pkt_set_segment_merging(struct pktcdvd_device *pd, struct request_queue *q)
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{
	if ((pd->settings.size << 9) / CD_FRAMESIZE <= q->max_phys_segments) {
		/*
		 * 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 <= q->max_phys_segments) {
		/*
		 * 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 {
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		printk(DRIVER_NAME": cdrom max_phys_segments too small\n");
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		return -EIO;
	}
}

/*
 * Copy CD_FRAMESIZE bytes from src_bio into a destination page
 */
static void pkt_copy_bio_data(struct bio *src_bio, int seg, int offs, struct page *dst_page, int dst_offs)
{
	unsigned int copy_size = CD_FRAMESIZE;

	while (copy_size > 0) {
		struct bio_vec *src_bvl = bio_iovec_idx(src_bio, seg);
		void *vfrom = kmap_atomic(src_bvl->bv_page, KM_USER0) +
			src_bvl->bv_offset + offs;
		void *vto = page_address(dst_page) + dst_offs;
		int len = min_t(int, copy_size, src_bvl->bv_len - offs);

		BUG_ON(len < 0);
		memcpy(vto, vfrom, len);
		kunmap_atomic(vfrom, KM_USER0);

		seg++;
		offs = 0;
		dst_offs += len;
		copy_size -= len;
	}
}

/*
 * Copy all data for this packet to pkt->pages[], so that
 * a) The number of required segments for the write bio is minimized, which
 *    is necessary for some scsi controllers.
 * b) The data can be used as cache to avoid read requests if we receive a
 *    new write request for the same zone.
 */
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static void pkt_make_local_copy(struct packet_data *pkt, struct bio_vec *bvec)
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{
	int f, p, offs;

	/* Copy all data to pkt->pages[] */
	p = 0;
	offs = 0;
	for (f = 0; f < pkt->frames; f++) {
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		if (bvec[f].bv_page != pkt->pages[p]) {
			void *vfrom = kmap_atomic(bvec[f].bv_page, KM_USER0) + bvec[f].bv_offset;
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			void *vto = page_address(pkt->pages[p]) + offs;
			memcpy(vto, vfrom, CD_FRAMESIZE);
			kunmap_atomic(vfrom, KM_USER0);
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			bvec[f].bv_page = pkt->pages[p];
			bvec[f].bv_offset = offs;
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		} else {
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			BUG_ON(bvec[f].bv_offset != offs);
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		}
		offs += CD_FRAMESIZE;
		if (offs >= PAGE_SIZE) {
			offs = 0;
			p++;
		}
	}
}

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

	VPRINTK("pkt_end_io_read: bio=%p sec0=%llx sec=%llx err=%d\n", bio,
		(unsigned long long)pkt->sector, (unsigned long long)bio->bi_sector, err);

	if (err)
		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);
}

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

	VPRINTK("pkt_end_io_packet_write: id=%d, err=%d\n", pkt->id, err);

	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(!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);
	for (bio = pkt->orig_bios; bio; bio = bio->bi_next) {
		int first_frame = (bio->bi_sector - pkt->sector) / (CD_FRAMESIZE >> 9);
		int num_frames = bio->bi_size / CD_FRAMESIZE;
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		pd->stats.secs_w += num_frames * (CD_FRAMESIZE >> 9);
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		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);

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	if (pkt->cache_valid) {
		VPRINTK("pkt_gather_data: zone %llx cached\n",
			(unsigned long long)pkt->sector);
		goto out_account;
	}

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	/*
	 * Schedule reads for missing parts of the packet.
	 */
	for (f = 0; f < pkt->frames; f++) {
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		struct bio_vec *vec;

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		int p, offset;
		if (written[f])
			continue;
		bio = pkt->r_bios[f];
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		vec = bio->bi_io_vec;
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		bio_init(bio);
		bio->bi_max_vecs = 1;
		bio->bi_sector = pkt->sector + f * (CD_FRAMESIZE >> 9);
		bio->bi_bdev = pd->bdev;
		bio->bi_end_io = pkt_end_io_read;
		bio->bi_private = pkt;
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		bio->bi_io_vec = vec;
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		bio->bi_destructor = pkt_bio_destructor;
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		p = (f * CD_FRAMESIZE) / PAGE_SIZE;
		offset = (f * CD_FRAMESIZE) % PAGE_SIZE;
		VPRINTK("pkt_gather_data: 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->bi_rw = READ;
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		pkt_queue_bio(pd, bio);
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		frames_read++;
	}

out_account:
	VPRINTK("pkt_gather_data: 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;
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			return pkt;
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		}
	}
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	BUG();
	return NULL;
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}

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);
	}
}

/*
 * recover a failed write, query for relocation if possible
 *
 * returns 1 if recovery is possible, or 0 if not
 *
 */
static int pkt_start_recovery(struct packet_data *pkt)
{
	/*
	 * FIXME. We need help from the file system to implement
	 * recovery handling.
	 */
	return 0;
#if 0
	struct request *rq = pkt->rq;
	struct pktcdvd_device *pd = rq->rq_disk->private_data;
	struct block_device *pkt_bdev;
	struct super_block *sb = NULL;
	unsigned long old_block, new_block;
	sector_t new_sector;

	pkt_bdev = bdget(kdev_t_to_nr(pd->pkt_dev));
	if (pkt_bdev) {
		sb = get_super(pkt_bdev);
		bdput(pkt_bdev);
	}

	if (!sb)
		return 0;

	if (!sb->s_op || !sb->s_op->relocate_blocks)
		goto out;

	old_block = pkt->sector / (CD_FRAMESIZE >> 9);
	if (sb->s_op->relocate_blocks(sb, old_block, &new_block))
		goto out;

	new_sector = new_block * (CD_FRAMESIZE >> 9);
	pkt->sector = new_sector;

	pkt->bio->bi_sector = new_sector;
	pkt->bio->bi_next = NULL;
	pkt->bio->bi_flags = 1 << BIO_UPTODATE;
	pkt->bio->bi_idx = 0;

	BUG_ON(pkt->bio->bi_rw != (1 << BIO_RW));
	BUG_ON(pkt->bio->bi_vcnt != pkt->frames);
	BUG_ON(pkt->bio->bi_size != pkt->frames * CD_FRAMESIZE);
	BUG_ON(pkt->bio->bi_end_io != pkt_end_io_packet_write);
	BUG_ON(pkt->bio->bi_private != pkt);

	drop_super(sb);
	return 1;

out:
	drop_super(sb);
	return 0;
#endif
}

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;
	VPRINTK("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;
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	int wakeup;
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	VPRINTK("handle_queue\n");

	atomic_set(&pd->scan_queue, 0);

	if (list_empty(&pd->cdrw.pkt_free_list)) {
		VPRINTK("handle_queue: 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 = ZONE(bio->bi_sector, pd);
		list_for_each_entry(p, &pd->cdrw.pkt_active_list, list) {
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			if (p->sector == zone) {
				bio = NULL;
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				goto try_next_bio;
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			}
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		}
		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) {
		VPRINTK("handle_queue: no bio\n");
		return 0;
	}

	pkt = pkt_get_packet_data(pd, zone);

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

	/*
	 * Scan work queue for bios in the same zone and link them
	 * to this packet.
	 */
	spin_lock(&pd->lock);
	VPRINTK("pkt_handle_queue: looking for zone %llx\n", (unsigned long long)zone);
	while ((node = pkt_rbtree_find(pd, zone)) != NULL) {
		bio = node->bio;
		VPRINTK("pkt_handle_queue: found zone=%llx\n",
			(unsigned long long)ZONE(bio->bi_sector, pd));
		if (ZONE(bio->bi_sector, pd) != zone)
			break;
		pkt_rbtree_erase(pd, node);
		spin_lock(&pkt->lock);
		pkt_add_list_last(bio, &pkt->orig_bios, &pkt->orig_bios_tail);
		pkt->write_size += bio->bi_size / CD_FRAMESIZE;
		spin_unlock(&pkt->lock);
	}
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	/* 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);
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	spin_unlock(&pd->lock);
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	if (wakeup)
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		clear_bdi_congested(&pd->disk->queue->backing_dev_info, WRITE);
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	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)
{
	struct bio *bio;
	int f;
	int frames_write;
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	struct bio_vec *bvec = pkt->w_bio->bi_io_vec;
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	for (f = 0; f < pkt->frames; f++) {
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		bvec[f].bv_page = pkt->pages[(f * CD_FRAMESIZE) / PAGE_SIZE];
		bvec[f].bv_offset = (f * CD_FRAMESIZE) % PAGE_SIZE;
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	}

	/*
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	 * Fill-in bvec with data from orig_bios.
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	 */
	frames_write = 0;
	spin_lock(&pkt->lock);
	for (bio = pkt->orig_bios; bio; bio = bio->bi_next) {
		int segment = bio->bi_idx;
		int src_offs = 0;
		int first_frame = (bio->bi_sector - pkt->sector) / (CD_FRAMESIZE >> 9);
		int num_frames = bio->bi_size / CD_FRAMESIZE;
		BUG_ON(first_frame < 0);
		BUG_ON(first_frame + num_frames > pkt->frames);
		for (f = first_frame; f < first_frame + num_frames; f++) {
			struct bio_vec *src_bvl = bio_iovec_idx(bio, segment);

			while (src_offs >= src_bvl->bv_len) {
				src_offs -= src_bvl->bv_len;
				segment++;
				BUG_ON(segment >= bio->bi_vcnt);
				src_bvl = bio_iovec_idx(bio, segment);
			}

			if (src_bvl->bv_len - src_offs >= CD_FRAMESIZE) {
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				bvec[f].bv_page = src_bvl->bv_page;
				bvec[f].bv_offset = src_bvl->bv_offset + src_offs;
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			} else {
				pkt_copy_bio_data(bio, segment, src_offs,
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						  bvec[f].bv_page, bvec[f].bv_offset);
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			}
			src_offs += CD_FRAMESIZE;
			frames_write++;
		}
	}
	pkt_set_state(pkt, PACKET_WRITE_WAIT_STATE);
	spin_unlock(&pkt->lock);

	VPRINTK("pkt_start_write: Writing %d frames for zone %llx\n",
		frames_write, (unsigned long long)pkt->sector);
	BUG_ON(frames_write != pkt->write_size);

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

	/* Start the write request */
	bio_init(pkt->w_bio);
	pkt->w_bio->bi_max_vecs = PACKET_MAX_SIZE;
	pkt->w_bio->bi_sector = pkt->sector;
	pkt->w_bio->bi_bdev = pd->bdev;
	pkt->w_bio->bi_end_io = pkt_end_io_packet_write;
	pkt->w_bio->bi_private = pkt;
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	pkt->w_bio->bi_io_vec = bvec;
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	pkt->w_bio->bi_destructor = pkt_bio_destructor;
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	for (f = 0; f < pkt->frames; f++)
		if (!bio_add_page(pkt->w_bio, bvec[f].bv_page, CD_FRAMESIZE, bvec[f].bv_offset))
			BUG();
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	VPRINTK(DRIVER_NAME": vcnt=%d\n", pkt->w_bio->bi_vcnt);
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	atomic_set(&pkt->io_wait, 1);
	pkt->w_bio->bi_rw = WRITE;
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	pkt_queue_bio(pd, pkt->w_bio);
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}

static void pkt_finish_packet(struct packet_data *pkt, int uptodate)
{
	struct bio *bio, *next;

	if (!uptodate)
		pkt->cache_valid = 0;

	/* Finish all bios corresponding to this packet */
	bio = pkt->orig_bios;
	while (bio) {
		next = bio->bi_next;
		bio->bi_next = NULL;
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		bio_endio(bio, uptodate ? 0 : -EIO);
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