out_vfree:
if (dev->data)
vfree(dev->data);
}

static int __init sbull_init(void)
{
int i;
/*
* Get registered.
*/
// printk("<0>" "add by lht\n");
sbull_major = register_blkdev(sbull_major, "sbull");
if (sbull_major <= 0) {
printk(KERN_WARNING "sbull: unable to get major number\n");
return -EBUSY;
}
/*
* Allocate the device array, and initialize each one.
*/
Devices = kmalloc(ndevices*sizeof (struct sbull_dev), GFP_KERNEL);
if (Devices == NULL)
goto out_unregister;
for (i = 0; i < ndevices; i++)
setup_device(Devices + i, i);

return 0;

out_unregister:
unregister_blkdev(sbull_major, "sbd");
return -ENOMEM;
}

static void sbull_exit(void)
{
int i;

for (i = 0; i < ndevices; i++) {
struct sbull_dev *dev = Devices + i;

del_timer_sync(&dev->timer);
if (dev->gd) {
del_gendisk(dev->gd);
put_disk(dev->gd);
}
if (dev->queue) {
if (request_mode == RM_NOQUEUE)
// blk_put_queue(dev->queue);
kobject_put(&(dev->queue)->kobj);
else
blk_cleanup_queue(dev->queue);
}
if (dev->data)
vfree(dev->data);
}
unregister_blkdev(sbull_major, "sbull");
kfree(Devices);
}

module_init(sbull_init);
module_exit(sbull_exit);

测试方法：

# Makefile
ifeq ($(KERNELRELEASE),)

#KERNELDIR = /home/lht/kernel2.6/linux-2.6.14

KERNELDIR = /lib/modules/$(shell uname -r)/build M=$(PWD) modules
PWD := $(shell pwd)

modules:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

modules_install:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install

clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions

.PHONY: modules modules_install clean

else
obj-m := sbull.o
endif

将模块插入内核（2.6.27）
root@linuxidc:/source/workplace/test/sbull_linuxidc# insmod sbull.ko
用lsmod查看模块是否成功插入内核
root@linuxidc:/source/workplace/test/sbull_linuxidc# lsmod | grep sbu
sbull 13452 0
出现上面结果，说明成功了
用ls查看/dev下是否有sbull设备
root@linuxidc:/source/workplace/test/sbull_linuxidc# ls /dev | grep sbu
sbulla
出现上面结果，说明有了，如果没有，用命令
mknod /dev/sbulla b 254 0
手动创建
至此，已经有一个块设备了
下面用fdisk对虚拟块设备分区
root@linuxidc:/source/workplace/test/sbull_linuxidc# fdisk /dev/sbulla
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x14d0973f.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)