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,                   /* readpage */
  47         NULL,                   /* writepage */
  48         NULL,                   /* bmap */
  49         NULL,                   /* truncate */
  50         NULL,                   /* permission */
  51         NULL                    /* smap */
  52 };
  53
  54 static struct dentry * ext2_follow_link(struct dentry * dentry,
  55                                         struct dentry *base,
  56                                         unsigned int follow)
  57 {
  58         struct inode *inode = dentry->d_inode;
  59         struct buffer_head * bh = NULL;
  60         int error;
  61         char * link;
  62
  63         link = (char *) inode->u.ext2_i.i_data;
  64         if (inode->i_blocks) {
  65                 if (!(bh = ext2_bread (inode, 0, 0, &error))) {
  66                         dput(base);
  67                         return ERR_PTR(-EIO);
  68                 }
  69                 link = bh->b_data;
  70         }
  71         UPDATE_ATIME(inode);
  72         base = lookup_dentry(link, base, follow);
  73         if (bh)
  74                 brelse(bh);
  75         return base;
  76 }
  77
  78 static int ext2_readlink (struct dentry * dentry, char * buffer, int buflen)
  79 {
  80         struct inode *inode = dentry->d_inode;
  81         struct buffer_head * bh = NULL;
  82         char * link;
  83         int i;
  84
  85         if (buflen > inode->i_sb->s_blocksize - 1)
  86                 buflen = inode->i_sb->s_blocksize - 1;
  87
  88         link = (char *) inode->u.ext2_i.i_data;
  89         if (inode->i_blocks) {
  90                 int err;
  91                 bh = ext2_bread (inode, 0, 0, &err);
  92                 if (!bh) {
  93                         if(err < 0) /* indicate type of error */
  94                                 return err;
  95                         return 0;
  96                 }
  97                 link = bh->b_data;
  98         }
  99
 100         i = 0;
 101         while (i < buflen && link[i])
 102                 i++;
 103         if (copy_to_user(buffer, link, i))
 104                 i = -EFAULT;
 105         UPDATE_ATIME(inode);
 106         if (bh)
 107                 brelse (bh);
 108         return i;
 109 }