genhd.c

Linux块设备驱动源码

/*
 *  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;
}

#ifdef CONFIG_PROC_FS
/* get block device names in somewhat random order */
int get_blkdev_list(char *p, int used)
{
	struct blk_major_name *n;
	int i, len;

	len = snprintf(p, (PAGE_SIZE-used), "\nBlock devices:\n");

	down(&block_subsys_sem);
	for (i = 0; i < ARRAY_SIZE(major_names); i++) {
		for (n = major_names[i]; n; n = n->next) {
			/*
			 * If the curent string plus the 5 extra characters
			 * in the line would run us off the page, then we're done
			 */
			if ((len + used + strlen(n->name) + 5) >= PAGE_SIZE)
				goto page_full;
			len += sprintf(p+len, "%3d %s\n",
				       n->major, n->name);
		}
	}
page_full:
	up(&block_subsys_sem);

	return len;
}
#endif

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;
		*n = p->next;
	}
	up(&block_subsys_sem);
	kfree(p);

	return ret;
}

EXPORT_SYMBOL(unregister_blkdev);

static struct kobj_map *bdev_map;

/*
 * Register device numbers dev..(dev+range-1)
 * range must be nonzero
 * The hash chain is sorted on range, so that subranges can override.
 */
void blk_register_region(dev_t dev, unsigned long range, struct module *module,
			 struct kobject *(*probe)(dev_t, int *, void *),
			 int (*lock)(dev_t, void *), void *data)
{
	kobj_map(bdev_map, dev, range, module, probe, lock, data);
}

EXPORT_SYMBOL(blk_register_region);

void blk_unregister_region(dev_t dev, unsigned long range)
{
	kobj_unmap(bdev_map, dev, range);
}

EXPORT_SYMBOL(blk_unregister_region);

static struct kobject *exact_match(dev_t dev, int *part, void *data)
{
	struct gendisk *p = data;
	return &p->kobj;
}

static int exact_lock(dev_t dev, void *data)
{
	struct gendisk *p = data;

	if (!get_disk(p))
		return -1;
	return 0;
}

/**
 * add_disk - add partitioning information to kernel list
 * @disk: per-device partitioning information
 *
 * This function registers the partitioning information in @disk
 * with the kernel.
 */
void add_disk(struct gendisk *disk)
{
	disk->flags |= GENHD_FL_UP;
	blk_register_region(MKDEV(disk->major, disk->first_minor),
			    disk->minors, NULL, exact_match, exact_lock, disk);
	register_disk(disk);
	blk_register_queue(disk);
}

EXPORT_SYMBOL(add_disk);
EXPORT_SYMBOL(del_gendisk);	/* in partitions/check.c */

void unlink_gendisk(struct gendisk *disk)
{
	blk_unregister_queue(disk);
	blk_unregister_region(MKDEV(disk->major, disk->first_minor),
			      disk->minors);
}

#define to_disk(obj) container_of(obj,struct gendisk,kobj)

/**
 * get_gendisk - get partitioning information for a given device
 * @dev: device to get partitioning information for
 *
 * This function gets the structure containing partitioning
 * information for the given device @dev.
 */
struct gendisk *get_gendisk(dev_t dev, int *part)
{
	struct kobject *kobj = kobj_lookup(bdev_map, dev, part);
	return  kobj ? to_disk(kobj) : NULL;
}

#ifdef CONFIG_PROC_FS
/* iterator */
static void *part_start(struct seq_file *part, loff_t *pos)
{
	struct list_head *p;
	loff_t l = *pos;

	down(&block_subsys_sem);
	list_for_each(p, &block_subsys.kset.list)
		if (!l--)
			return list_entry(p, struct gendisk, kobj.entry);
	return NULL;
}

static void *part_next(struct seq_file *part, void *v, loff_t *pos)
{
	struct list_head *p = ((struct gendisk *)v)->kobj.entry.next;
	++*pos;
	return p==&block_subsys.kset.list ? NULL : 
		list_entry(p, struct gendisk, kobj.entry);
}

static void part_stop(struct seq_file *part, void *v)
{
	up(&block_subsys_sem);
}

static int show_partition(struct seq_file *part, void *v)
{
	struct gendisk *sgp = v;
	int n;
	char buf[BDEVNAME_SIZE];

	if (&sgp->kobj.entry == block_subsys.kset.list.next)
		seq_puts(part, "major minor  #blocks  name\n\n");

	/* Don't show non-partitionable removeable devices or empty devices */
	if (!get_capacity(sgp) ||
			(sgp->minors == 1 && (sgp->flags & GENHD_FL_REMOVABLE)))
		return 0;
	if (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)
		return 0;

	/* show the full disk and all non-0 size partitions of it */
	seq_printf(part, "%4d  %4d %10llu %s\n",
		sgp->major, sgp->first_minor,
		(unsigned long long)get_capacity(sgp) >> 1,
		disk_name(sgp, 0, buf));
	for (n = 0; n < sgp->minors - 1; n++) {
		if (!sgp->part[n])
			continue;
		if (sgp->part[n]->nr_sects == 0)
			continue;
		seq_printf(part, "%4d  %4d %10llu %s\n",
			sgp->major, n + 1 + sgp->first_minor,
			(unsigned long long)sgp->part[n]->nr_sects >> 1 ,
			disk_name(sgp, n + 1, buf));
	}

	return 0;
}

struct seq_operations partitions_op = {
	.start =part_start,
	.next =	part_next,
	.stop =	part_stop,
	.show =	show_partition
};
#endif


extern int blk_dev_init(void);

static struct kobject *base_probe(dev_t dev, int *part, void *data)
{
	if (request_module("block-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
		/* Make old-style 2.4 aliases work */
		request_module("block-major-%d", MAJOR(dev));
	return NULL;
}

static int __init genhd_device_init(void)
{
	bdev_map = kobj_map_init(base_probe, &block_subsys_sem);
	blk_dev_init();
	subsystem_register(&block_subsys);
	return 0;
}

subsys_initcall(genhd_device_init);



/*
 * kobject & sysfs bindings for block devices
 */
static ssize_t disk_attr_show(struct kobject *kobj, struct attribute *attr,
			      char *page)
{
	struct gendisk *disk = to_disk(kobj);
	struct disk_attribute *disk_attr =
		container_of(attr,struct disk_attribute,attr);
	ssize_t ret = -EIO;

	if (disk_attr->show)
		ret = disk_attr->show(disk,page);
	return ret;
}

static struct sysfs_ops disk_sysfs_ops = {
	.show	= &disk_attr_show,
};

static ssize_t disk_dev_read(struct gendisk * disk, char *page)
{
	dev_t base = MKDEV(disk->major, disk->first_minor); 
	return print_dev_t(page, base);
}
static ssize_t disk_range_read(struct gendisk * disk, char *page)
{
	return sprintf(page, "%d\n", disk->minors);
}