i386/linux-2.3.21/fs/ext2/symlink.c

   1 /*
   2  *  linux/fs/ext2/symlink.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  *
   9  *  from
  10  *
  11  *  linux/fs/minix/symlink.c
  12  *
  13  *  Copyright (C) 1991, 1992  Linus Torvalds
  14  *
  15  *  ext2 symlink handling code
  16  */
  17
  18 #include <asm/uaccess.h>
  19
  20 #include <linux/errno.h>
  21 #include <linux/fs.h>
  22 #include <linux/ext2_fs.h>
  23 #include <linux/sched.h>
  24 #include <linux/mm.h>
  25 #include <linux/stat.h>
  26
  27 static int ext2_readlink (struct dentry *, char *, int);
  28 static struct dentry *ext2_follow_link(struct dentry *, struct dentry *, unsigned int);
  29
  30 /*
  31  * symlinks can't do much...
  32  */
  33 struct inode_operations ext2_symlink_inode_operations = {
  34         NULL,                   /* no file-operations */
  35         NULL,                   /* create */
  36         NULL,                   /* lookup */
  37         NULL,                   /* link */
  38         NULL,                   /* unlink */
  39         NULL,                   /* symlink */
  40         NULL,                   /* mkdir */
  41         NULL,                   /* rmdir */
  42         NULL,                   /* mknod */
  43         NULL,                   /* rename */
  44         ext2_readlink,          /* readlink */
  45         ext2_follow_link,       /* follow_link */
  46         NULL,                   /* get_block */
  47         NULL,                   /* readpage */
  48         NULL,                   /* writepage */
  49         NULL,                   /* flushpage */
  50         NULL,                   /* truncate */
  51         NULL,                   /* permission */
  52         NULL,                   /* smap */
  53         NULL                    /* revalidate */
  54 };
  55
  56 static struct dentry * ext2_follow_link(struct dentry * dentry,
  57                                         struct dentry *base,
  58                                         unsigned int follow)
  59 {
  60         struct inode *inode = dentry->d_inode;
  61         struct buffer_head * bh = NULL;
  62         int error;
  63         char * link;
  64
  65         link = (char *) inode->u.ext2_i.i_data;
  66         if (inode->i_blocks) {
  67                 if (!(bh = ext2_bread (inode, 0, 0, &error))) {
  68                         dput(base);
  69                         return ERR_PTR(-EIO);
  70                 }
  71                 link = bh->b_data;
  72         }
  73         UPDATE_ATIME(inode);
  74         base = lookup_dentry(link, base, follow);
  75         if (bh)
  76                 brelse(bh);
  77         return base;
  78 }
  79
  80 static int ext2_readlink (struct dentry * dentry, char * buffer, int buflen)
  81 {
  82         struct inode *inode = dentry->d_inode;
  83         struct buffer_head * bh = NULL;
  84         char * link;
  85         int i;
  86
  87         if (buflen > inode->i_sb->s_blocksize - 1)
  88                 buflen = inode->i_sb->s_blocksize - 1;
  89
  90         link = (char *) inode->u.ext2_i.i_data;
  91         if (inode->i_blocks) {
  92                 int err;
  93                 bh = ext2_bread (inode, 0, 0, &err);
  94                 if (!bh) {
  95                         if(err < 0) /* indicate type of error */
  96                                 return err;
  97                         return 0;
  98                 }
  99                 link = bh->b_data;
 100         }
 101
 102         i = 0;
 103         while (i < buflen && link[i])
 104                 i++;
 105         if (copy_to_user(buffer, link, i))
 106                 i = -EFAULT;
 107         if (bh)
 108                 brelse (bh);
 109         return i;
 110 }