/* * This tries to keep block devices away from devfs as much as possible. */#include <linux/fs.h>#include <linux/devfs_fs_kernel.h>#include <linux/vmalloc.h>#include <linux/genhd.h>#include <linux/bitops.h>#include <linux/mutex.h>  struct unique_numspace {	u32		  num_free;          /*  Num free in bits       */	u32		  length;            /*  Array length in bytes  */	unsigned long	  *bits;	struct semaphore  mutex;}; static DEFINE_MUTEX(numspace_mutex); static int expand_numspace(struct unique_numspace *s){	u32 length;	void *bits; 	if (s->length < 16)		length = 16;	else		length = s->length << 1; 	bits = vmalloc(length);	if (!bits)		return -ENOMEM;	if (s->bits) {		memcpy(bits, s->bits, s->length);		vfree(s->bits);	}			s->num_free = (length - s->length) << 3;	s->bits = bits;	memset(bits + s->length, 0, length - s->length);	s->length = length; 	return 0;} static int alloc_unique_number(struct unique_numspace *s){	int rval = 0; 	mutex_lock(&numspace_mutex);	if (s->num_free < 1)		rval = expand_numspace(s);	if (!rval) {		rval = find_first_zero_bit(s->bits, s->length << 3);		--s->num_free;		__set_bit(rval, s->bits);	}	mutex_unlock(&numspace_mutex); 	return rval;} static void dealloc_unique_number(struct unique_numspace *s, int number){	int old_val; 	if (number >= 0) {		mutex_lock(&numspace_mutex);		old_val = __test_and_clear_bit(number, s->bits);		if (old_val)			++s->num_free;		mutex_unlock(&numspace_mutex);	}} static struct unique_numspace disc_numspace;static struct unique_numspace cdrom_numspace; void devfs_add_partitioned(struct gendisk *disk){	char dirname[64], symlink[16]; 	devfs_mk_dir(disk->devfs_name);	devfs_mk_bdev(MKDEV(disk->major, disk->first_minor),			S_IFBLK|S_IRUSR|S_IWUSR,			"%s/disc", disk->devfs_name); 	disk->number = alloc_unique_number(&disc_numspace); 	sprintf(symlink, "discs/disc%d", disk->number);	sprintf(dirname, "../%s", disk->devfs_name);	devfs_mk_symlink(symlink, dirname); } void devfs_add_disk(struct gendisk *disk){	devfs_mk_bdev(MKDEV(disk->major, disk->first_minor),			(disk->flags & GENHD_FL_CD) ?				S_IFBLK|S_IRUGO|S_IWUGO :				S_IFBLK|S_IRUSR|S_IWUSR,			"%s", disk->devfs_name); 	if (disk->flags & GENHD_FL_CD) {		char dirname[64], symlink[16]; 		disk->number = alloc_unique_number(&cdrom_numspace); 		sprintf(symlink, "cdroms/cdrom%d", disk->number);		sprintf(dirname, "../%s", disk->devfs_name);		devfs_mk_symlink(symlink, dirname);	}} void devfs_remove_disk(struct gendisk *disk){	if (disk->minors != 1) {		devfs_remove("discs/disc%d", disk->number);		dealloc_unique_number(&disc_numspace, disk->number);		devfs_remove("%s/disc", disk->devfs_name);	}	if (disk->flags & GENHD_FL_CD) {		devfs_remove("cdroms/cdrom%d", disk->number);		dealloc_unique_number(&cdrom_numspace, disk->number);	}	devfs_remove(disk->devfs_name);}