seq_file接口处理链表

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/net.h>
#include <net/sock.h>
#include <linux/in.h>
#include <linux/types.h>
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <asm-generic/unaligned.h>
#include <linux/sysctl.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <asm/checksum.h>
#include <linux/ip.h>
#include <linux/workqueue.h>
#include <linux/jiffies.h>
#include <net/net_namespace.h>
#include <net/route.h>
#include <linux/route.h>
#include <linux/stddef.h>
#include <linux/mutex.h>

#define err(msg) printk(KERN_ERR "%s failed.\n", msg)

struct list_data_struct {
    struct list_head n_list;
    int v;
};

static struct mutex lock;
static struct list_head head;

static void * myproc_seq_start(struct seq_file *seq, loff_t *pos)
{
    mutex_lock(&lock);
    return seq_list_start(&head, *pos);
}

static void * myproc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    return seq_list_next(v, &head, pos);
}

static void myproc_seq_stop(struct seq_file *seq, void *v)
{
    mutex_unlock(&lock);
}

static int myproc_seq_show(struct seq_file *seq, void *v)
{
    struct list_data_struct *item = list_entry(v, struct list_data_struct, n_list);
    
    seq_printf(seq, "value = %d\n", item->v);
    return 0;
}

static struct seq_operations myproc_seq_ops = {
    .start    = myproc_seq_start,
    .next    = myproc_seq_next,
    .stop    = myproc_seq_stop,
    .show    = myproc_seq_show,
};

static int myproc_open(struct inode *inodp, struct file *filp)
{
    return seq_open(filp, &myproc_seq_ops);
}

static struct file_operations myproc_fops = {
    .owner        = THIS_MODULE,
    .open        = myproc_open,
    .read        = seq_read,
    .llseek        = seq_lseek,    
    .release     = seq_release,
};

static int __init myproc_init(void)
{
    struct list_data_struct *item;
    int i;

    mutex_init(&lock);
    INIT_LIST_HEAD(&head);

    for (i = 0; i < 10; i++) {
        item = kzalloc(sizeof(struct list_data_struct), GFP_KERNEL);
        if (item == NULL) {
            err("kzalloc");
            continue;
        }

        item->v = i;
        list_add_tail(&item->n_list, &head);
    }

    proc_net_fops_create(&init_net, "myproc", 0, &myproc_fops);
    return 0;
}

static void __exit myproc_exit(void)
{
    struct list_data_struct *pos, *n;

    proc_net_remove(&init_net, "myproc");
    list_for_each_entry_safe(pos, n, &head, n_list) {
        kfree(pos);
    }
}

MODULE_LICENSE("GPL");

module_init(myproc_init);
module_exit(myproc_exit);