pktcdvd.c

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/*
 * Copyright (C) 2000 Jens Axboe <[e-mail]>
 * Copyright (C) 2001-2004 Peter Osterlund <[e-mail]>
 * Copyright (C) 2006 Thomas Maier <[e-mail]>
 *
 * 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 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.
 *
 *************************************************************************/

#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>
#include <linux/freezer.h>
#include <linux/mutex.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi.h>
#include <linux/debugfs.h>
#include <linux/device.h>

#include <asm/uaccess.h>

#define DRIVER_NAME	"pktcdvd"

#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;
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 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;
	p = kzalloc(sizeof(*p), GFP_KERNEL);
	if (!p)
		return NULL;
	kobject_set_name(&p->kobj, "%s", name);
	p->kobj.parent = parent;
	p->kobj.ktype = ktype;
	p->pd = pd;
	if (kobject_register(&p->kobj) != 0) {
		kobject_put(&p->kobj);
		return NULL;
	}
	return p;
}
/*
 * remove a pktcdvd kernel object.
 */
static void pkt_kobj_remove(struct pktcdvd_kobj *p)
{
	if (p)
		kobject_unregister(&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 <[e-mail]>
 *
 **********************************************************/

#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 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->clsdev = class_device_create(class_pktcdvd,
					NULL, pd->pkt_dev,
					NULL, "%s", pd->name);
		if (IS_ERR(pd->clsdev))
			pd->clsdev = NULL;
	}
	if (pd->clsdev) {
		pd->kobj_stat = pkt_kobj_create(pd, "stat",
					&pd->clsdev->kobj,
					&kobj_pkt_type_stat);
		pd->kobj_wqueue = pkt_kobj_create(pd, "write_queue",
					&pd->clsdev->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)
		class_device_destroy(class_pktcdvd, pd->pkt_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 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;

	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 ssize_t class_pktcdvd_store_remove(struct class *c, 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 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);
}

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_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;
}

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


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)) {
		VPRINTK(DRIVER_NAME": queue empty\n");
		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);
}