path: root/block/genhd.c

/*
 *  gendisk handling
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/genhd.h>
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/kobj_map.h>
#include <linux/buffer_head.h>

#define MAX_PROBE_HASH 255	/* random */

static struct subsystem block_subsys;

static DECLARE_MUTEX(block_subsys_sem);

/*
 * Can be deleted altogether. Later.
 *
 */
static struct blk_major_name {
	struct blk_major_name *next;
	int major;
	char name[16];
} *major_names[MAX_PROBE_HASH];

/* index in the above - for now: assume no multimajor ranges */
static inline int major_to_index(int major)
{
	return major % MAX_PROBE_HASH;
}

struct blkdev_info {
        int index;
        struct blk_major_name *bd;
};

/*
 * iterate over a list of blkdev_info structures.  allows
 * the major_names array to be iterated over from outside this file
 * must be called with the block_subsys_sem held
 */
void *get_next_blkdev(void *dev)
{
        struct blkdev_info *info;

        if (dev == NULL) {
                info = kmalloc(sizeof(*info), GFP_KERNEL);
                if (!info)
                        goto out;
                info->index=0;
                info->bd = major_names[info->index];
                if (info->bd)
                        goto out;
        } else {
                info = dev;
        }

        while (info->index < ARRAY_SIZE(major_names)) {
                if (info->bd)
                        info->bd = info->bd->next;
                if (info->bd)
                        goto out;
                /*
                 * No devices on this chain, move to the next
                 */
                info->index++;
                info->bd = (info->index < ARRAY_SIZE(major_names)) ?
			major_names[info->index] : NULL;
                if (info->bd)
                        goto out;
        }

out:
        return info;
}

void *acquire_blkdev_list(void)
{
        down(&block_subsys_sem);
        return get_next_blkdev(NULL);
}

void release_blkdev_list(void *dev)
{
        up(&block_subsys_sem);
        kfree(dev);
}


/*
 * Count the number of records in the blkdev_list.
 * must be called with the block_subsys_sem held
 */
int count_blkdev_list(void)
{
	struct blk_major_name *n;
	int i, count;

	count = 0;

	for (i = 0; i < ARRAY_SIZE(major_names); i++) {
		for (n = major_names[i]; n; n = n->next)
				count++;
	}

	return count;
}

/*
 * extract the major and name values from a blkdev_info struct
 * passed in as a void to *dev.  Must be called with
 * block_subsys_sem held
 */
int get_blkdev_info(void *dev, int *major, char **name)
{
        struct blkdev_info *info = dev;

        if (info->bd == NULL)
                return 1;

        *major = info->bd->major;
        *name = info->bd->name;
        return 0;
}


int register_blkdev(unsigned int major, const char *name)
{
	struct blk_major_name **n, *p;
	int index, ret = 0;

	down(&block_subsys_sem);

	/* temporary */
	if (major == 0) {
		for (index = ARRAY_SIZE(major_names)-1; index > 0; index--) {
			if (major_names[index] == NULL)
				break;
		}

		if (index == 0) {
			printk("register_blkdev: failed to get major for %s\n",
			       name);
			ret = -EBUSY;
			goto out;
		}
		major = index;
		ret = major;
	}

	p = kmalloc(sizeof(struct blk_major_name), GFP_KERNEL);
	if (p == NULL) {
		ret = -ENOMEM;
		goto out;
	}

	p->major = major;
	strlcpy(p->name, name, sizeof(p->name));
	p->next = NULL;
	index = major_to_index(major);

	for (n = &major_names[index]; *n; n = &(*n)->next) {
		if ((*n)->major == major)
			break;
	}
	if (!*n)
		*n = p;
	else
		ret = -EBUSY;

	if (ret < 0) {
		printk("register_blkdev: cannot get major %d for %s\n",
		       major, name);
		kfree(p);
	}
out:
	up(&block_subsys_sem);
	return ret;
}

EXPORT_SYMBOL(register_blkdev);

/* todo: make void - error printk here */
int unregister_blkdev(unsigned int major, const char *name)
{
	struct blk_major_name **n;
	struct blk_major_name *p = NULL;
	int index = major_to_index(major);
	int ret = 0;

	down(&block_subsys_sem);
	for (n = &major_names[index]; *n; n = &(*n)->next)
		if ((*n)->major == major)
			break;
	if (!*n || strcmp((*n)->name, name))
		ret = -EINVAL;
	else {
		p = *n;