fs/sysv/symlink.c

   1 /*
   2  *  linux/fs/sysv/symlink.c
   3  *
   4  *  minix/symlink.c
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  *
   7  *  coh/symlink.c
   8  *  Copyright (C) 1993  Pascal Haible, Bruno Haible
   9  *
  10  *  sysv/symlink.c
  11  *  Copyright (C) 1993  Bruno Haible
  12  *
  13  *  SystemV/Coherent symlink handling code
  14  */
  15
  16 #include <linux/errno.h>
  17 #include <linux/sched.h>
  18 #include <linux/sysv_fs.h>
  19 #include <linux/stat.h>
  20
  21 #include <asm/uaccess.h>
  22
  23 static int sysv_readlink(struct dentry *, char *, int);
  24 static struct dentry *sysv_follow_link(struct dentry *, struct dentry *, unsigned int);
  25
  26 /*
  27  * symlinks can't do much...
  28  */
  29 struct inode_operations sysv_symlink_inode_operations = {
  30         NULL,                   /* no file-operations */
  31         NULL,                   /* create */
  32         NULL,                   /* lookup */
  33         NULL,                   /* link */
  34         NULL,                   /* unlink */
  35         NULL,                   /* symlink */
  36         NULL,                   /* mkdir */
  37         NULL,                   /* rmdir */
  38         NULL,                   /* mknod */
  39         NULL,                   /* rename */
  40         sysv_readlink,          /* readlink */
  41         sysv_follow_link,       /* follow_link */
  42         NULL,                   /* get_block */
  43         NULL,                   /* readpage */
  44         NULL,                   /* writepage */
  45         NULL,                   /* flushpage */
  46         NULL,                   /* truncate */
  47         NULL,                   /* permission */
  48         NULL,                   /* smap */
  49         NULL                    /* revalidate */
  50 };
  51
  52 static struct dentry *sysv_follow_link(struct dentry * dentry,
  53                                         struct dentry * base,
  54                                         unsigned int follow)
  55 {
  56         struct inode *inode = dentry->d_inode;
  57         struct buffer_head * bh;
  58
  59         bh = sysv_file_bread(inode, 0, 0);
  60         if (!bh) {
  61                 dput(base);
  62                 return ERR_PTR(-EIO);
  63         }
  64         UPDATE_ATIME(inode);
  65         base = lookup_dentry(bh->b_data, base, follow);
  66         brelse(bh);
  67         return base;
  68 }
  69
  70 static int sysv_readlink(struct dentry * dentry, char * buffer, int buflen)
  71 {
  72         struct inode *inode = dentry->d_inode;
  73         struct buffer_head * bh;
  74         char * bh_data;
  75         int i;
  76         char c;
  77
  78         if (buflen > inode->i_sb->sv_block_size_1)
  79                 buflen = inode->i_sb->sv_block_size_1;
  80         bh = sysv_file_bread(inode, 0, 0);
  81         if (!bh)
  82                 return 0;
  83         bh_data = bh->b_data;
  84         i = 0;
  85         while (i<buflen && (c = bh_data[i])) {
  86                 i++;
  87                 put_user(c,buffer++);
  88         }
  89         brelse(bh);
  90         return i;
  91 }