內(nèi)核直接讀取硬盤固定扇區(qū)的代碼

highnjupt

塊緩存 struct buffer_head 用來(lái)保存從磁盤讀取到的數(shù)據(jù)，而 struct page 是文件的緩存，在文件層面上的數(shù)據(jù)會(huì)緩存到page里，所以內(nèi)核里直接讀取某個(gè)固定的扇區(qū)可以利用 struct buffer_head，讀取的速度會(huì)快一些；以下是實(shí)現(xiàn)的代碼：

#include linux/module.h>
#include linux/init.h>
#include linux/sched.h>
#include linux/kernel.h>
#include linux/fs.h>
#include linux/types.h>
#include linux/buffer_head.h>
#include linux/blkdev.h>
#include linux/msdos_fs.h>
#include linux/fcntl.h>
#include linux/delay.h>
static int set_size = 512;
static int nr = -1;
static char *devn = "/dev/sda";
module_param(set_size,int,S_IRUGO);
MODULE_PARM_DESC(set_size,"how many bytes you want to read,not more than 4096");
module_param(nr,long,S_IRUGO);
MODULE_PARM_DESC(nr,"which sectors you want to read");
module_param(devn,charp,S_IRUGO);
MODULE_PARM_DESC(devn,"which device");
MODULE_LICENSE("GPL");
static struct block_device *bdev;
static char *usage = "You can change the value:set_size nr devn";
static int __init init_read(void)
{
    struct buffer_head *bh = NULL;
    int size;
    if(nr == -1)
    {
        printk("Using this programm,you need set \"nr\"\n");
        printk("%s\n",usage);
        return -1;
    }
    printk("read disk\n");
    bdev = open_bdev_excl(devn,0x8000,NULL);
    if(IS_ERR(bdev))
    {
        printk("open failed\n");
        return PTR_ERR(bdev);
    }
   
    size = bdev_hardsect_size(bdev);
    printk("size = %d\n",size);
   
    if(set_blocksize(bdev,set_size)){
        printk("set block size error\n");
        return -1;
    }
    /* read disk */
    bh = __bread(bdev,nr,set_size);
    if(bh == NULL)
        return 0;
    //if you want to modify the disk contents,do this operations
    memset(bh->b_data,0x30,set_size);
    set_buffer_uptodate(bh);
    /* write disk */
    mark_buffer_dirty(bh);
    if(bh)
        brelse(bh);
    return 0;
}
static void __exit exit_read(void)
{
    printk("exit\n");
    close_bdev_excl(bdev);
}
module_init(init_read);
module_exit(exit_read);


本文來(lái)自ChinaUnix博客，如果查看原文請(qǐng)點(diǎn)：http://blog.chinaunix.net/u3/101879/showart_2124877.html