linux怎么实现软链接相关的功能

/* *  linux/fs/minix/symlink.c * *  Copyright (C) 1991, 1992  Linus Torvalds * *  minix symlink handling code */#ifdef MODULE#include <linux/module.h>#endif#include <asm/segment.h>#include <linux/errno.h>#include <linux/sched.h>#include <linux/fs.h>#include <linux/minix_fs.h>#include <linux/stat.h>static int minix_readlink(struct inode *, char *, int);static int minix_follow_link(struct inode *, struct inode *, int, int, struct inode **);/* * symlinks can't do much... */// 操作软链接文件的函数集，在新建软链接文件的时候赋值给inode结构体struct inode_operations minix_symlink_inode_operations = {  NULL,      /* no file-operations */  NULL,      /* create */  NULL,      /* lookup */  NULL,      /* link */  NULL,      /* unlink */  NULL,      /* symlink */  NULL,      /* mkdir */  NULL,      /* rmdir */  NULL,      /* mknod */  NULL,      /* rename */  minix_readlink,    /* readlink */  minix_follow_link,  /* follow_link */  NULL,      /* bmap */  NULL,      /* truncate */  NULL      /* permission */};// 打开软链对应的文件static int minix_follow_link(struct inode * dir, struct inode * inode,  int flag, int mode, struct inode ** res_inode){  int error;  struct buffer_head * bh;  *res_inode = NULL;  if (!dir) {    dir = current->fs->root;    dir->i_count++;  }  if (!inode) {    iput(dir);    return -ENOENT;  }  if (!S_ISLNK(inode->i_mode)) {    iput(dir);    *res_inode = inode;    return 0;  }  if (current->link_count > 5) {    iput(inode);    iput(dir);    return -ELOOP;  }  // 读取文件第一块内容  if (!(bh = minix_bread(inode, 0, 0))) {    iput(inode);    iput(dir);    return -EIO;  }  iput(inode);  current->link_count++;  // 打开b_data里的保存的文件名对应的文件  error = open_namei(bh->b_data,flag,mode,res_inode,dir);  current->link_count--;  brelse(bh);  return error;}// 读取软链文件的内容，即文件路径static int minix_readlink(struct inode * inode, char * buffer, int buflen){  struct buffer_head * bh;  int i;  char c;  if (!S_ISLNK(inode->i_mode)) {    iput(inode);    return -EINVAL;  }  if (buflen > 1023)    buflen = 1023;  bh = minix_bread(inode, 0, 0);  iput(inode);  if (!bh)    return 0;  i = 0;  while (i<buflen && (c = bh->b_data[i])) {    i++;    put_fs_byte(c,buffer++);  }  brelse(bh);  return i;}