drivers/mtd/mtd_blkdevs.c - kernel/msm-4.19 - Gitiles

 /*
  * (C) 2003 David Woodhouse <dwmw2@infradead.org>
  *
  * Interface to Linux 2.5 block layer for MTD 'translation layers'.
  *
  */

 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/fs.h>
 #include <linux/mtd/blktrans.h>
 #include <linux/mtd/mtd.h>
 #include <linux/blkdev.h>
 #include <linux/blkpg.h>
 #include <linux/freezer.h>
 #include <linux/spinlock.h>
 #include <linux/hdreg.h>
 #include <linux/init.h>
 #include <linux/mutex.h>
 #include <linux/kthread.h>
 #include <asm/uaccess.h>

 #include "mtdcore.h"

 static LIST_HEAD(blktrans_majors);

 struct mtd_blkcore_priv {
 	struct task_struct *thread;
 	struct request_queue *rq;
 	spinlock_t queue_lock;
 };

 static int blktrans_discard_request(struct request_queue *q,
 				    struct request *req)
 {
 	req->cmd_type = REQ_TYPE_LINUX_BLOCK;
 	req->cmd[0] = REQ_LB_OP_DISCARD;
 	return 0;
 }

 static int do_blktrans_request(struct mtd_blktrans_ops *tr,
 			       struct mtd_blktrans_dev *dev,
 			       struct request *req)
 {
 	unsigned long block, nsect;
 	char *buf;

 	block = blk_rq_pos(req) << 9 >> tr->blkshift;
 	nsect = blk_rq_cur_bytes(req) >> tr->blkshift;

 	buf = req->buffer;

 	if (req->cmd_type == REQ_TYPE_LINUX_BLOCK &&
 	    req->cmd[0] == REQ_LB_OP_DISCARD)
 		return tr->discard(dev, block, nsect);

 	if (!blk_fs_request(req))
 		return -EIO;

 	if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
 	    get_capacity(req->rq_disk))
 		return -EIO;

 	switch(rq_data_dir(req)) {
 	case READ:
 		for (; nsect > 0; nsect--, block++, buf += tr->blksize)
 			if (tr->readsect(dev, block, buf))
 				return -EIO;
 		return 0;

 	case WRITE:
 		if (!tr->writesect)
 			return -EIO;

 		for (; nsect > 0; nsect--, block++, buf += tr->blksize)
 			if (tr->writesect(dev, block, buf))
 				return -EIO;
 		return 0;

 	default:
 		printk(KERN_NOTICE "Unknown request %u\n", rq_data_dir(req));
 		return -EIO;
 	}
 }

 static int mtd_blktrans_thread(void *arg)
 {
 	struct mtd_blktrans_ops *tr = arg;
 	struct request_queue *rq = tr->blkcore_priv->rq;
 	struct request *req = NULL;

 	/* we might get involved when memory gets low, so use PF_MEMALLOC */
 	current->flags |= PF_MEMALLOC;

 	spin_lock_irq(rq->queue_lock);

 	while (!kthread_should_stop()) {
 		struct mtd_blktrans_dev *dev;
 		int res;

 		if (!req && !(req = blk_fetch_request(rq))) {
 			set_current_state(TASK_INTERRUPTIBLE);
 			spin_unlock_irq(rq->queue_lock);
 			schedule();
 			spin_lock_irq(rq->queue_lock);
 			continue;
 		}

 		dev = req->rq_disk->private_data;
 		tr = dev->tr;

 		spin_unlock_irq(rq->queue_lock);

 		mutex_lock(&dev->lock);
 		res = do_blktrans_request(tr, dev, req);
 		mutex_unlock(&dev->lock);

 		spin_lock_irq(rq->queue_lock);

 		if (!__blk_end_request_cur(req, res))
 			req = NULL;
 	}

 	if (req)
 		__blk_end_request_all(req, -EIO);

 	spin_unlock_irq(rq->queue_lock);

 	return 0;
 }

 static void mtd_blktrans_request(struct request_queue *rq)
 {
 	struct mtd_blktrans_ops *tr = rq->queuedata;
 	wake_up_process(tr->blkcore_priv->thread);
 }


 static int blktrans_open(struct block_device *bdev, fmode_t mode)
 {
 	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
 	struct mtd_blktrans_ops *tr = dev->tr;
 	int ret = -ENODEV;

 	if (!try_module_get(dev->mtd->owner))
 		goto out;

 	if (!try_module_get(tr->owner))
 		goto out_tr;

 	/* FIXME: Locking. A hot pluggable device can go away
 	   (del_mtd_device can be called for it) without its module
 	   being unloaded. */
 	dev->mtd->usecount++;

 	ret = 0;
 	if (tr->open && (ret = tr->open(dev))) {
 		dev->mtd->usecount--;
 		module_put(dev->mtd->owner);
 	out_tr:
 		module_put(tr->owner);
 	}
  out:
 	return ret;
 }

 static int blktrans_release(struct gendisk *disk, fmode_t mode)
 {
 	struct mtd_blktrans_dev *dev = disk->private_data;
 	struct mtd_blktrans_ops *tr = dev->tr;
 	int ret = 0;

 	if (tr->release)
 		ret = tr->release(dev);

 	if (!ret) {
 		dev->mtd->usecount--;
 		module_put(dev->mtd->owner);
 		module_put(tr->owner);
 	}

 	return ret;
 }

 static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 {
 	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;

 	if (dev->tr->getgeo)
 		return dev->tr->getgeo(dev, geo);
 	return -ENOTTY;
 }

 static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
 			      unsigned int cmd, unsigned long arg)
 {
 	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
 	struct mtd_blktrans_ops *tr = dev->tr;

 	switch (cmd) {
 	case BLKFLSBUF:
 		if (tr->flush)
 			return tr->flush(dev);
 		/* The core code did the work, we had nothing to do. */
 		return 0;
 	default:
 		return -ENOTTY;
 	}
 }

 static struct block_device_operations mtd_blktrans_ops = {
 	.owner		= THIS_MODULE,
 	.open		= blktrans_open,
 	.release	= blktrans_release,
 	.locked_ioctl	= blktrans_ioctl,
 	.getgeo		= blktrans_getgeo,
 };

 int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
 {
 	struct mtd_blktrans_ops *tr = new->tr;
 	struct mtd_blktrans_dev *d;
 	int last_devnum = -1;
 	struct gendisk *gd;

 	if (mutex_trylock(&mtd_table_mutex)) {
 		mutex_unlock(&mtd_table_mutex);
 		BUG();
 	}

 	list_for_each_entry(d, &tr->devs, list) {
 		if (new->devnum == -1) {
 			/* Use first free number */
 			if (d->devnum != last_devnum+1) {
 				/* Found a free devnum. Plug it in here */
 				new->devnum = last_devnum+1;
 				list_add_tail(&new->list, &d->list);
 				goto added;
 			}
 		} else if (d->devnum == new->devnum) {
 			/* Required number taken */
 			return -EBUSY;
 		} else if (d->devnum > new->devnum) {
 			/* Required number was free */
 			list_add_tail(&new->list, &d->list);
 			goto added;
 		}
 		last_devnum = d->devnum;
 	}
 	if (new->devnum == -1)
 		new->devnum = last_devnum+1;

 	if ((new->devnum << tr->part_bits) > 256) {
 		return -EBUSY;
 	}

 	list_add_tail(&new->list, &tr->devs);
  added:
 	mutex_init(&new->lock);
 	if (!tr->writesect)
 		new->readonly = 1;

 	gd = alloc_disk(1 << tr->part_bits);
 	if (!gd) {
 		list_del(&new->list);
 		return -ENOMEM;
 	}
 	gd->major = tr->major;
 	gd->first_minor = (new->devnum) << tr->part_bits;
 	gd->fops = &mtd_blktrans_ops;

 	if (tr->part_bits)
 		if (new->devnum < 26)
 			snprintf(gd->disk_name, sizeof(gd->disk_name),
 				 "%s%c", tr->name, 'a' + new->devnum);
 		else
 			snprintf(gd->disk_name, sizeof(gd->disk_name),
 				 "%s%c%c", tr->name,
 				 'a' - 1 + new->devnum / 26,
 				 'a' + new->devnum % 26);
 	else
 		snprintf(gd->disk_name, sizeof(gd->disk_name),
 			 "%s%d", tr->name, new->devnum);

 	/* 2.5 has capacity in units of 512 bytes while still
 	   having BLOCK_SIZE_BITS set to 10. Just to keep us amused. */
 	set_capacity(gd, (new->size * tr->blksize) >> 9);

 	gd->private_data = new;
 	new->blkcore_priv = gd;
 	gd->queue = tr->blkcore_priv->rq;
 	gd->driverfs_dev = &new->mtd->dev;

 	if (new->readonly)
 		set_disk_ro(gd, 1);

 	add_disk(gd);

 	return 0;
 }

 int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
 {
 	if (mutex_trylock(&mtd_table_mutex)) {
 		mutex_unlock(&mtd_table_mutex);
 		BUG();
 	}

 	list_del(&old->list);

 	del_gendisk(old->blkcore_priv);
 	put_disk(old->blkcore_priv);

 	return 0;
 }

 static void blktrans_notify_remove(struct mtd_info *mtd)
 {
 	struct mtd_blktrans_ops *tr;
 	struct mtd_blktrans_dev *dev, *next;

 	list_for_each_entry(tr, &blktrans_majors, list)
 		list_for_each_entry_safe(dev, next, &tr->devs, list)
 			if (dev->mtd == mtd)
 				tr->remove_dev(dev);
 }

 static void blktrans_notify_add(struct mtd_info *mtd)
 {
 	struct mtd_blktrans_ops *tr;

 	if (mtd->type == MTD_ABSENT)
 		return;

 	list_for_each_entry(tr, &blktrans_majors, list)
 		tr->add_mtd(tr, mtd);
 }

 static struct mtd_notifier blktrans_notifier = {
 	.add = blktrans_notify_add,
 	.remove = blktrans_notify_remove,
 };

 int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
 {
 	int ret, i;

 	/* Register the notifier if/when the first device type is
 	   registered, to prevent the link/init ordering from fucking
 	   us over. */
 	if (!blktrans_notifier.list.next)
 		register_mtd_user(&blktrans_notifier);

 	tr->blkcore_priv = kzalloc(sizeof(*tr->blkcore_priv), GFP_KERNEL);
 	if (!tr->blkcore_priv)
 		return -ENOMEM;

 	mutex_lock(&mtd_table_mutex);

 	ret = register_blkdev(tr->major, tr->name);
 	if (ret) {
 		printk(KERN_WARNING "Unable to register %s block device on major %d: %d\n",
 		       tr->name, tr->major, ret);
 		kfree(tr->blkcore_priv);
 		mutex_unlock(&mtd_table_mutex);
 		return ret;
 	}
 	spin_lock_init(&tr->blkcore_priv->queue_lock);

 	tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
 	if (!tr->blkcore_priv->rq) {
 		unregister_blkdev(tr->major, tr->name);
 		kfree(tr->blkcore_priv);
 		mutex_unlock(&mtd_table_mutex);
 		return -ENOMEM;
 	}

 	tr->blkcore_priv->rq->queuedata = tr;
 	blk_queue_logical_block_size(tr->blkcore_priv->rq, tr->blksize);
 	if (tr->discard)
 		blk_queue_set_discard(tr->blkcore_priv->rq,
 				      blktrans_discard_request);

 	tr->blkshift = ffs(tr->blksize) - 1;

 	tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread, tr,
 			"%sd", tr->name);
 	if (IS_ERR(tr->blkcore_priv->thread)) {
 		int ret = PTR_ERR(tr->blkcore_priv->thread);
 		blk_cleanup_queue(tr->blkcore_priv->rq);
 		unregister_blkdev(tr->major, tr->name);
 		kfree(tr->blkcore_priv);
 		mutex_unlock(&mtd_table_mutex);
 		return ret;
 	}

 	INIT_LIST_HEAD(&tr->devs);
 	list_add(&tr->list, &blktrans_majors);

 	for (i=0; i<MAX_MTD_DEVICES; i++) {
 		if (mtd_table[i] && mtd_table[i]->type != MTD_ABSENT)
 			tr->add_mtd(tr, mtd_table[i]);
 	}

 	mutex_unlock(&mtd_table_mutex);

 	return 0;
 }

 int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
 {
 	struct mtd_blktrans_dev *dev, *next;

 	mutex_lock(&mtd_table_mutex);

 	/* Clean up the kernel thread */
 	kthread_stop(tr->blkcore_priv->thread);

 	/* Remove it from the list of active majors */
 	list_del(&tr->list);

 	list_for_each_entry_safe(dev, next, &tr->devs, list)
 		tr->remove_dev(dev);

 	blk_cleanup_queue(tr->blkcore_priv->rq);
 	unregister_blkdev(tr->major, tr->name);

 	mutex_unlock(&mtd_table_mutex);

 	kfree(tr->blkcore_priv);

 	BUG_ON(!list_empty(&tr->devs));
 	return 0;
 }

 static void __exit mtd_blktrans_exit(void)
 {
 	/* No race here -- if someone's currently in register_mtd_blktrans
 	   we're screwed anyway. */
 	if (blktrans_notifier.list.next)
 		unregister_mtd_user(&blktrans_notifier);
 }

 module_exit(mtd_blktrans_exit);

 EXPORT_SYMBOL_GPL(register_mtd_blktrans);
 EXPORT_SYMBOL_GPL(deregister_mtd_blktrans);
 EXPORT_SYMBOL_GPL(add_mtd_blktrans_dev);
 EXPORT_SYMBOL_GPL(del_mtd_blktrans_dev);

 MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Common interface to block layer for MTD 'translation layers'");
	/*
	* (C) 2003 David Woodhouse <dwmw2@infradead.org>
	*
	* Interface to Linux 2.5 block layer for MTD 'translation layers'.
	*
	*/

	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/module.h>
	#include <linux/list.h>
	#include <linux/fs.h>
	#include <linux/mtd/blktrans.h>
	#include <linux/mtd/mtd.h>
	#include <linux/blkdev.h>
	#include <linux/blkpg.h>
	#include <linux/freezer.h>
	#include <linux/spinlock.h>
	#include <linux/hdreg.h>
	#include <linux/init.h>
	#include <linux/mutex.h>
	#include <linux/kthread.h>
	#include <asm/uaccess.h>

	#include "mtdcore.h"

	static LIST_HEAD(blktrans_majors);

	struct mtd_blkcore_priv {
	struct task_struct *thread;
	struct request_queue *rq;
	spinlock_t queue_lock;
	};

	static int blktrans_discard_request(struct request_queue *q,
	struct request *req)
	{
	req->cmd_type = REQ_TYPE_LINUX_BLOCK;
	req->cmd[0] = REQ_LB_OP_DISCARD;
	return 0;
	}

	static int do_blktrans_request(struct mtd_blktrans_ops *tr,
	struct mtd_blktrans_dev *dev,
	struct request *req)
	{
	unsigned long block, nsect;
	char *buf;

	block = blk_rq_pos(req) << 9 >> tr->blkshift;
	nsect = blk_rq_cur_bytes(req) >> tr->blkshift;

	buf = req->buffer;

	if (req->cmd_type == REQ_TYPE_LINUX_BLOCK &&
	req->cmd[0] == REQ_LB_OP_DISCARD)
	return tr->discard(dev, block, nsect);

	if (!blk_fs_request(req))
	return -EIO;

	if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
	get_capacity(req->rq_disk))
	return -EIO;

	switch(rq_data_dir(req)) {
	case READ:
	for (; nsect > 0; nsect--, block++, buf += tr->blksize)
	if (tr->readsect(dev, block, buf))
	return -EIO;
	return 0;

	case WRITE:
	if (!tr->writesect)
	return -EIO;

	for (; nsect > 0; nsect--, block++, buf += tr->blksize)
	if (tr->writesect(dev, block, buf))
	return -EIO;
	return 0;

	default:
	printk(KERN_NOTICE "Unknown request %u\n", rq_data_dir(req));
	return -EIO;
	}
	}

	static int mtd_blktrans_thread(void *arg)
	{
	struct mtd_blktrans_ops *tr = arg;
	struct request_queue *rq = tr->blkcore_priv->rq;
	struct request *req = NULL;

	/* we might get involved when memory gets low, so use PF_MEMALLOC */
	current->flags \|= PF_MEMALLOC;

	spin_lock_irq(rq->queue_lock);

	while (!kthread_should_stop()) {
	struct mtd_blktrans_dev *dev;
	int res;

	if (!req && !(req = blk_fetch_request(rq))) {
	set_current_state(TASK_INTERRUPTIBLE);
	spin_unlock_irq(rq->queue_lock);
	schedule();
	spin_lock_irq(rq->queue_lock);
	continue;
	}

	dev = req->rq_disk->private_data;
	tr = dev->tr;

	spin_unlock_irq(rq->queue_lock);

	mutex_lock(&dev->lock);
	res = do_blktrans_request(tr, dev, req);
	mutex_unlock(&dev->lock);

	spin_lock_irq(rq->queue_lock);

	if (!__blk_end_request_cur(req, res))
	req = NULL;
	}

	if (req)
	__blk_end_request_all(req, -EIO);

	spin_unlock_irq(rq->queue_lock);

	return 0;
	}

	static void mtd_blktrans_request(struct request_queue *rq)
	{
	struct mtd_blktrans_ops *tr = rq->queuedata;
	wake_up_process(tr->blkcore_priv->thread);
	}


	static int blktrans_open(struct block_device *bdev, fmode_t mode)
	{
	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
	struct mtd_blktrans_ops *tr = dev->tr;
	int ret = -ENODEV;

	if (!try_module_get(dev->mtd->owner))
	goto out;

	if (!try_module_get(tr->owner))
	goto out_tr;

	/* FIXME: Locking. A hot pluggable device can go away
	(del_mtd_device can be called for it) without its module
	being unloaded. */
	dev->mtd->usecount++;

	ret = 0;
	if (tr->open && (ret = tr->open(dev))) {
	dev->mtd->usecount--;
	module_put(dev->mtd->owner);
	out_tr:
	module_put(tr->owner);
	}
	out:
	return ret;
	}

	static int blktrans_release(struct gendisk *disk, fmode_t mode)
	{
	struct mtd_blktrans_dev *dev = disk->private_data;
	struct mtd_blktrans_ops *tr = dev->tr;
	int ret = 0;

	if (tr->release)
	ret = tr->release(dev);

	if (!ret) {
	dev->mtd->usecount--;
	module_put(dev->mtd->owner);
	module_put(tr->owner);
	}

	return ret;
	}

	static int blktrans_getgeo(struct block_device bdev, struct hd_geometry geo)
	{
	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;

	if (dev->tr->getgeo)
	return dev->tr->getgeo(dev, geo);
	return -ENOTTY;
	}

	static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
	unsigned int cmd, unsigned long arg)
	{
	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
	struct mtd_blktrans_ops *tr = dev->tr;

	switch (cmd) {
	case BLKFLSBUF:
	if (tr->flush)
	return tr->flush(dev);
	/* The core code did the work, we had nothing to do. */
	return 0;
	default:
	return -ENOTTY;
	}
	}

	static struct block_device_operations mtd_blktrans_ops = {
	.owner = THIS_MODULE,
	.open = blktrans_open,
	.release = blktrans_release,
	.locked_ioctl = blktrans_ioctl,
	.getgeo = blktrans_getgeo,
	};

	int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
	{
	struct mtd_blktrans_ops *tr = new->tr;
	struct mtd_blktrans_dev *d;
	int last_devnum = -1;
	struct gendisk *gd;

	if (mutex_trylock(&mtd_table_mutex)) {
	mutex_unlock(&mtd_table_mutex);
	BUG();
	}

	list_for_each_entry(d, &tr->devs, list) {
	if (new->devnum == -1) {
	/* Use first free number */
	if (d->devnum != last_devnum+1) {
	/* Found a free devnum. Plug it in here */
	new->devnum = last_devnum+1;
	list_add_tail(&new->list, &d->list);
	goto added;
	}
	} else if (d->devnum == new->devnum) {
	/* Required number taken */
	return -EBUSY;
	} else if (d->devnum > new->devnum) {
	/* Required number was free */
	list_add_tail(&new->list, &d->list);
	goto added;
	}
	last_devnum = d->devnum;
	}
	if (new->devnum == -1)
	new->devnum = last_devnum+1;

	if ((new->devnum << tr->part_bits) > 256) {
	return -EBUSY;
	}

	list_add_tail(&new->list, &tr->devs);
	added:
	mutex_init(&new->lock);
	if (!tr->writesect)
	new->readonly = 1;

	gd = alloc_disk(1 << tr->part_bits);
	if (!gd) {
	list_del(&new->list);
	return -ENOMEM;
	}
	gd->major = tr->major;
	gd->first_minor = (new->devnum) << tr->part_bits;
	gd->fops = &mtd_blktrans_ops;

	if (tr->part_bits)
	if (new->devnum < 26)
	snprintf(gd->disk_name, sizeof(gd->disk_name),
	"%s%c", tr->name, 'a' + new->devnum);
	else
	snprintf(gd->disk_name, sizeof(gd->disk_name),
	"%s%c%c", tr->name,
	'a' - 1 + new->devnum / 26,
	'a' + new->devnum % 26);
	else
	snprintf(gd->disk_name, sizeof(gd->disk_name),
	"%s%d", tr->name, new->devnum);

	/* 2.5 has capacity in units of 512 bytes while still
	having BLOCK_SIZE_BITS set to 10. Just to keep us amused. */
	set_capacity(gd, (new->size * tr->blksize) >> 9);

	gd->private_data = new;
	new->blkcore_priv = gd;
	gd->queue = tr->blkcore_priv->rq;
	gd->driverfs_dev = &new->mtd->dev;

	if (new->readonly)
	set_disk_ro(gd, 1);

	add_disk(gd);

	return 0;
	}

	int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
	{
	if (mutex_trylock(&mtd_table_mutex)) {
	mutex_unlock(&mtd_table_mutex);
	BUG();
	}

	list_del(&old->list);

	del_gendisk(old->blkcore_priv);
	put_disk(old->blkcore_priv);

	return 0;
	}

	static void blktrans_notify_remove(struct mtd_info *mtd)
	{
	struct mtd_blktrans_ops *tr;
	struct mtd_blktrans_dev dev, next;

	list_for_each_entry(tr, &blktrans_majors, list)
	list_for_each_entry_safe(dev, next, &tr->devs, list)
	if (dev->mtd == mtd)
	tr->remove_dev(dev);
	}

	static void blktrans_notify_add(struct mtd_info *mtd)
	{
	struct mtd_blktrans_ops *tr;

	if (mtd->type == MTD_ABSENT)
	return;

	list_for_each_entry(tr, &blktrans_majors, list)
	tr->add_mtd(tr, mtd);
	}

	static struct mtd_notifier blktrans_notifier = {
	.add = blktrans_notify_add,
	.remove = blktrans_notify_remove,
	};

	int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
	{
	int ret, i;

	/* Register the notifier if/when the first device type is
	registered, to prevent the link/init ordering from fucking
	us over. */
	if (!blktrans_notifier.list.next)
	register_mtd_user(&blktrans_notifier);

	tr->blkcore_priv = kzalloc(sizeof(*tr->blkcore_priv), GFP_KERNEL);
	if (!tr->blkcore_priv)
	return -ENOMEM;

	mutex_lock(&mtd_table_mutex);

	ret = register_blkdev(tr->major, tr->name);
	if (ret) {
	printk(KERN_WARNING "Unable to register %s block device on major %d: %d\n",
	tr->name, tr->major, ret);
	kfree(tr->blkcore_priv);
	mutex_unlock(&mtd_table_mutex);
	return ret;
	}
	spin_lock_init(&tr->blkcore_priv->queue_lock);

	tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
	if (!tr->blkcore_priv->rq) {
	unregister_blkdev(tr->major, tr->name);
	kfree(tr->blkcore_priv);
	mutex_unlock(&mtd_table_mutex);
	return -ENOMEM;
	}

	tr->blkcore_priv->rq->queuedata = tr;
	blk_queue_logical_block_size(tr->blkcore_priv->rq, tr->blksize);
	if (tr->discard)
	blk_queue_set_discard(tr->blkcore_priv->rq,
	blktrans_discard_request);

	tr->blkshift = ffs(tr->blksize) - 1;

	tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread, tr,
	"%sd", tr->name);
	if (IS_ERR(tr->blkcore_priv->thread)) {
	int ret = PTR_ERR(tr->blkcore_priv->thread);
	blk_cleanup_queue(tr->blkcore_priv->rq);
	unregister_blkdev(tr->major, tr->name);
	kfree(tr->blkcore_priv);
	mutex_unlock(&mtd_table_mutex);
	return ret;
	}

	INIT_LIST_HEAD(&tr->devs);
	list_add(&tr->list, &blktrans_majors);

	for (i=0; i<MAX_MTD_DEVICES; i++) {
	if (mtd_table[i] && mtd_table[i]->type != MTD_ABSENT)
	tr->add_mtd(tr, mtd_table[i]);
	}

	mutex_unlock(&mtd_table_mutex);

	return 0;
	}

	int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
	{
	struct mtd_blktrans_dev dev, next;

	mutex_lock(&mtd_table_mutex);

	/* Clean up the kernel thread */
	kthread_stop(tr->blkcore_priv->thread);

	/* Remove it from the list of active majors */
	list_del(&tr->list);

	list_for_each_entry_safe(dev, next, &tr->devs, list)
	tr->remove_dev(dev);

	blk_cleanup_queue(tr->blkcore_priv->rq);
	unregister_blkdev(tr->major, tr->name);

	mutex_unlock(&mtd_table_mutex);

	kfree(tr->blkcore_priv);

	BUG_ON(!list_empty(&tr->devs));
	return 0;
	}

	static void __exit mtd_blktrans_exit(void)
	{
	/* No race here -- if someone's currently in register_mtd_blktrans
	we're screwed anyway. */
	if (blktrans_notifier.list.next)
	unregister_mtd_user(&blktrans_notifier);
	}

	module_exit(mtd_blktrans_exit);

	EXPORT_SYMBOL_GPL(register_mtd_blktrans);
	EXPORT_SYMBOL_GPL(deregister_mtd_blktrans);
	EXPORT_SYMBOL_GPL(add_mtd_blktrans_dev);
	EXPORT_SYMBOL_GPL(del_mtd_blktrans_dev);

	MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("Common interface to block layer for MTD 'translation layers'");