实现过aio_read的大神过来瞧瞧

[lucky-lucky]

《linux device driver》源码当中的scullp实现了aio_read和aio_write，现在我把代码都编译过去了，使用下面的代码做测试，却发现内核并没有调用scullp的aio_read函数，而是调用了read函数。

#include <sys/types.h>
#include <aio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>

#define SIZE_TO_READ 100

int main()
{
    char buffer[SIZE_TO_READ] = {0};;
    struct aiocb cb;
    int file = 0;
    int numBytes = 0;
    file = open("/dev/scullp", O_RDONLY, 0);

    if (file == -1)
    {
        perror("Unable to open file!");
        return 1;
    }

    memset(&cb, 0, sizeof(struct aiocb));
    cb.aio_nbytes = SIZE_TO_READ;
    cb.aio_fildes = file;
    cb.aio_offset = 0;
    cb.aio_buf = buffer;

    if (aio_read(&cb) == -1)
    {
        perror("Unable to create request!" );
        close(file);
    }

    printf("Request enqueued!\n");

    while(aio_error(&cb) == EINPROGRESS)
    {
        printf("working...\n");
    }

    numBytes = aio_return(&cb);

    if (numBytes != -1)
    {
        printf("success!read:%s\n",buffer);
    }
    else
    {
        perror("aio_return error\n");
    }

    close(file);

    return 0;
}

scullp当中的部分代码如下：

static ssize_t scullp_aio_read(struct kiocb *iocb, char __user *buf, size_t count,
		loff_t pos)
{
    printk(KERN_INFO "scullp_aio_read\n");
	return scullp_defer_op(0, iocb, buf, count, pos);
}

ssize_t scullp_read (struct file *filp, char __user *buf, size_t count,
                loff_t *f_pos)
{
    ....
    printk(KERN_INFO "scullp_read\n");
    .....
}

在shell当中执行

#gcc aio_test.c -lrt
#./a.out
Request enqueued!
working...
working...
working...
working...
success!read:
#dmesg | tail
.....
[180293.021298] scullp_read

要如何使内核调用aio_read函数而不是read函数？请大神支支招，谢谢。