块设备驱动注意事项
将ldd3（linxu device driver 3）中块设备驱动部分的代码在redhat6.3下编译时，会出现很多问题，主要是由于ldd3示例代码使用的内核版本较低（2.6.10版本），
对于块设备子系统，很多接口都已经发生了改变，
主要有如下变化：
1，elv_next_request已删除，使用如下方式从请求队列中获取请求
struct request *req;
req = blk_fetch_request (q);
while(req != NULL){
struct sbull_dev *dev = req->rq_disk->private_data;
if(req->cmd_type != REQ_TYPE_FS){
printk(KERN_NOTICE "Skip non-fs request\n");
blk_end_request_all(req,-EIO);
continue;
}
sbull_transfer(dev,blk_rq_pos(req),blk_rq_cur_sectors(req),
req->buffer,rq_data_dir(req));
if(!blk_end_request_cur(req,0)){
req = NULL;
}
}
其中blk_peek_request从队列中获取请求，但是不会从队列中删除该请求。
从队列中删除请求需要调用blk_start_request()，blk_fetch_request 相当于调用blk_peek_request，和blk_start_request()
具体参考：http://lwn.net/Articles/333620/,
2，end_request，改成了blk_end_request_all
3，现在不能直接获取request结构的sector和current_nr_sector；而是通过函数blk_rq_pos和blk_rq_cur_sectors获得，所以将对用两处改为：
sbull_transfer(dev, blk_rq_pos(req), blk_rq_cur_sectors(req), req->buffer, rq_data_dir(req));
4，bio_endio参数过多
5，blk_queue_hardsect_size定义已删除，使用blk_queue_logical_block_size(dev->queue, hardsect_size);
6，block_device_operation接口已经发生了非常大的变化
新接口如下：（该接口包含getgeo函数，从而不再需要在ioctl函数实现HDIO_GETGEO命令）
struct block_device_operations {
int (*open) (struct block_device *, fmode_t);
int (*release) (struct gendisk *, fmode_t);
int (*locked_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
int (*direct_access) (struct block_device *, sector_t,
void **, unsigned long *);
int (*media_changed) (struct gendisk *);
unsigned long long (*set_capacity) (struct gendisk *,
unsigned long long);
int (*revalidate_disk) (struct gendisk *);
int (*getgeo)(struct block_device *, struct hd_geometry *);
/* this callback is with swap_lock and sometimes page table lock held */
void (*swap_slot_free_notify) (struct block_device *, unsigned long);
struct module *owner;
};
编译通过后就可以使用该设备，例如
创建分区：
fdisk /dev/sbulla
创建文件系统
mkfs.ext3 /dev/sbulla1
修改后的代码如下：
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/types.h> /* size_t */
#include <linux/fcntl.h> /* O_ACCMODE */
#include <linux/hdreg.h> /* HDIO_GETGEO */
#include <linux/kdev_t.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h> /* invalidate_bdev */
#include <linux/bio.h>
MODULE_LICENSE("Dual BSD/GPL");
static int sbull_major = 0;
module_param(sbull_major,int,0);
static int hardsect_size =512;
module_param(hardsect_size,int,0);
static int nsectors = 1024;
module_param(nsectors,int,0);
static int ndevices = 4;
module_param(ndevices,int,0);
enum {
RM_SIMPLE = 0,
RM_FULL = 1,
RM_NOQUEUE = 2,
};
static int request_mode = RM_SIMPLE;
module_param(request_mode, int, 0);
#define SBULL_MINORS 16
#define KERNEL_SECTOR_SIZE 512
#define INVALIDATE_DELAY 30*HZ
struct sbull_dev{
int size;
u8 *data;
short users;
short media_change;
spinlock_t lock;
struct request_queue *queue;
struct gendisk *gd;
struct timer_list timer;
};
static struct sbull_dev *Devices = NULL;
static void sbull_transfer(struct sbull_dev *dev,unsigned long sector,unsigned long nsect,
char *buffer,int write)
{
unsigned long offset = sector * KERNEL_SECTOR_SIZE;
unsigned long nbytes = nsect * KERNEL_SECTOR_SIZE;
if((offset + nbytes) > dev->size) {
printk(KERN_NOTICE "Beyond-end write (%ld %ld)\n",offset,nbytes);
return;
}
if(write)
memcpy(dev->data + offset,buffer,nbytes);
else
memcpy(buffer,dev->data + offset,nbytes);
}
static void sbull_request(struct request_queue *q)
{
struct request *req;
req = blk_fetch_request(q);
while(req != NULL){
struct sbull_dev *dev = req->rq_disk->private_data;
if(req->cmd_type != REQ_TYPE_FS){
printk(KERN_NOTICE "Skip non-fs request\n");
blk_end_request_all(req,-EIO);
continue;
}
sbull_transfer(dev,blk_rq_pos(req),blk_rq_cur_sectors(req),
req->buffer,rq_data_dir(req));
if(!__blk_end_request_cur(req,0)){
req = NULL;
}
}
}
static int sbull_xfer_bio(struct sbull_dev *dev, struct bio *bio)
{
int i;
struct bio_vec *bvec;
sector_t sector = bio->bi_sector;
bio_for_each_segment(bvec,bio,i){
char *buffer = __bio_kmap_atomic(bio,i,KM_USER0);
sbull_transfer(dev,sector,bio_cur_bytes(bio)/KERNEL_SECTOR_SIZE,buffer,bio_data_dir(bio) == WRITE);
sector += bio_cur_bytes(bio)/KERNEL_SECTOR_SIZE;
__bio_kunmap_atomic(bio,KM_USER0);
}
return 0;
}
static int sbull_xfer_request(struct sbull_dev *dev,struct request *req)
{
struct bio *bio;
int nsect = 0;
__rq_for_each_bio(bio,req){
sbull_xfer_bio(dev,bio);
nsect += bio->bi_size / KERNEL_SECTOR_SIZE;
}
return nsect;
}
static void sbull_full_request(struct request_queue *q)
{
struct request *req;
struct sbull_dev *dev = q->queuedata;
req = blk_fetch_request(q);
while(req != NULL){
if(req->cmd_type != REQ_TYPE_FS){
printk(KERN_NOTICE "Skip non-fs request\n");
blk_end_request_all(req,-EIO);
continue;
}
sbull_xfer_request(dev,req);
if(!blk_end_request_cur(req,0)){
req = NULL;
}
}
}
static int sbull_make_request(struct request_queue *q,struct bio *bio)
{
struct sbull_dev *dev = q->queuedata;
int status;
status = sbull_xfer_bio(dev,bio);
bio_endio(bio,status);
return 0;
}
static int sbull_open(struct block_device *bd, fmode_t mode)
{
struct sbull_dev *dev = bd->bd_disk->private_data;
del_timer_sync(&dev->timer);
spin_lock(&dev->lock);
if(!dev->users)
check_disk_change(bd);
dev->users++;
spin_unlock(&dev->lock);
return 0;
}
static int sbull_release(struct gendisk *gd, fmode_t mode)
{
struct sbull_dev *dev = gd->private_data;
spin_lock(&dev->lock);
dev->users--;
if(!dev->users){
dev->timer.expires = jiffies + INVALIDATE_DELAY;
add_timer(&dev->timer);
}
spin_unlock(&dev->lock);
return 0;
}
int sbull_media_change(struct gendisk *gd)
{
struct sbull_dev *dev = gd->private_data;
return dev->media_change;
}
int sbull_revalidate(struct gendisk *gd)
{
struct sbull_dev *dev = gd->private_data;
if(dev->media_change){
dev->media_change = 0;
memset(dev->data,0,dev->size);
}
return 0;
}
void sbull_invalidate(unsigned long ldev)
{
struct sbull_dev *dev = (struct sbull_dev *)ldev;
spin_lock(&dev->lock);
if(dev->users || !dev->data)
printk (KERN_WARNING "sbull: timer sanity check failed\n");
else
dev->media_change = 1;
spin_unlock(&dev->lock);
}
int sbull_ioctl(struct block_device *bd, fmode_t mode, unsigned cmd, unsigned long arg)
{
return 0;
}
static int sbull_getgeo(struct block_device *bd, struct hd_geometry *geo)
{
long size;
struct sbull_dev *dev = bd->bd_disk->private_data;
size = dev->size *(hardsect_size / KERNEL_SECTOR_SIZE);
geo->cylinders = (size & ~0x3f) >> 6;
geo->heads = 4;
geo->sectors = 16;
geo->start = 4;
return 0;
}
static struct block_device_operations sbull_ops = {
.owner = THIS_MODULE,
.open = sbull_open,
.release = sbull_release,
.media_changed = sbull_media_change,
.revalidate_disk = sbull_revalidate,
.ioctl = sbull_ioctl,
.getgeo = sbull_getgeo
};
static void setup_device(struct sbull_dev *dev,int which)
{
printk(KERN_WARNING "sbull: step into into setup_device\n");
memset(dev,0,sizeof(struct sbull_dev));
dev->size = nsectors * hardsect_size;
dev->data = vmalloc(dev->size);
if(dev->data == NULL){
printk(KERN_NOTICE "vmalloc failure\n");
return;
}
spin_lock_init(&dev->lock);
init_timer(&dev->timer);
dev->timer.data = (unsigned long)dev;
dev->timer.function = sbull_invalidate;
switch(request_mode){
case RM_NOQUEUE:
dev->queue = blk_alloc_queue(GFP_KERNEL);
if(dev->queue == NULL)
goto out_vfree;
blk_queue_make_request(dev->queue,sbull_make_request);
break;
case RM_FULL:
dev->queue = blk_init_queue(sbull_full_request,&dev->lock);
if(dev->queue == NULL)
goto out_vfree;
break;
case RM_SIMPLE:
dev->queue = blk_init_queue(sbull_request,&dev->lock);
if(dev->queue == NULL)
goto out_vfree;
break;
default:
printk(KERN_NOTICE "Bad request mode %d, using simple\n", request_mode);
}
blk_queue_logical_block_size(dev->queue,hardsect_size);
dev->queue->queuedata = dev;
dev->gd = alloc_disk(SBULL_MINORS);
if(!dev->gd){
printk(KERN_NOTICE "alloc_disk failure\n");
goto out_vfree;
}
dev->gd->major = sbull_major;
dev->gd->first_minor = which * SBULL_MINORS;
dev->gd->fops = &sbull_ops;
dev->gd->queue = dev->queue;
dev->gd->private_data = dev;
snprintf(dev->gd->disk_name,32,"sbull%c",which + 'a');
set_capacity(dev->gd,nsectors * (hardsect_size / KERNEL_SECTOR_SIZE));
add_disk(dev->gd);
return;
out_vfree:
if(dev->data)
vfree(dev->data);
}
static int __init sbull_init(void)
{
int i;
printk(KERN_WARNING "sbull: start init\n");
sbull_major = register_blkdev(sbull_major,"sbull");
if (sbull_major <= 0) {
printk(KERN_WARNING "sbull: unable to get major number\n");
return -EBUSY;
}
printk(KERN_WARNING "sbull: start kmalloc\n");
Devices = kmalloc(ndevices * sizeof(struct sbull_dev),GFP_KERNEL);
if(Devices == NULL)
goto out_unregister;
printk(KERN_WARNING "sbull: start setup_device\n");
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)
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);