fs/udf/symlink.c

   1 /*
   2  * symlink.c
   3  *
   4  * PURPOSE
   5  *      Symlink handling routines for the OSTA-UDF(tm) filesystem.
   6  *
   7  * COPYRIGHT
   8  *      This file is distributed under the terms of the GNU General Public
   9  *      License (GPL). Copies of the GPL can be obtained from:
  10  *              ftp://prep.ai.mit.edu/pub/gnu/GPL
  11  *      Each contributing author retains all rights to their own work.
  12  *
  13  *  (C) 1998-2001 Ben Fennema
  14  *  (C) 1999 Stelias Computing Inc
  15  *
  16  * HISTORY
  17  *
  18  *  04/16/99 blf  Created.
  19  *
  20  */
  21
  22 #include "udfdecl.h"
  23 #include <asm/uaccess.h>
  24 #include <linux/errno.h>
  25 #include <linux/fs.h>
  26 #include <linux/time.h>
  27 #include <linux/mm.h>
  28 #include <linux/stat.h>
  29 #include <linux/pagemap.h>
  30 #include <linux/buffer_head.h>
  31 #include "udf_i.h"
  32
  33 static void udf_pc_to_char(struct super_block *sb, unsigned char *from,
  34                            int fromlen, unsigned char *to)
  35 {
  36         struct pathComponent *pc;
  37         int elen = 0;
  38         unsigned char *p = to;
  39
  40         while (elen < fromlen) {
  41                 pc = (struct pathComponent *)(from + elen);
  42                 switch (pc->componentType) {
  43                 case 1:
  44                         if (pc->lengthComponentIdent == 0) {
  45                                 p = to;
  46                                 *p++ = '/';
  47                         }
  48                         break;
  49                 case 3:
  50                         memcpy(p, "../", 3);
  51                         p += 3;
  52                         break;
  53                 case 4:
  54                         memcpy(p, "./", 2);
  55                         p += 2;
  56                         /* that would be . - just ignore */
  57                         break;
  58                 case 5:
  59                         p += udf_get_filename(sb, pc->componentIdent, p,
  60                                               pc->lengthComponentIdent);
  61                         *p++ = '/';
  62                         break;
  63                 }
  64                 elen += sizeof(struct pathComponent) + pc->lengthComponentIdent;
  65         }
  66         if (p > to + 1)
  67                 p[-1] = '\0';
  68         else
  69                 p[0] = '\0';
  70 }
  71
  72 static int udf_symlink_filler(struct file *file, struct page *page)
  73 {
  74         struct inode *inode = page->mapping->host;
  75         struct buffer_head *bh = NULL;
  76         unsigned char *symlink;
  77         int err;
  78         unsigned char *p = kmap(page);
  79         struct udf_inode_info *iinfo;
  80         uint32_t pos;
  81
  82         /* We don't support symlinks longer than one block */
  83         if (inode->i_size > inode->i_sb->s_blocksize) {
  84                 err = -ENAMETOOLONG;
  85                 goto out_unmap;
  86         }
  87
  88         iinfo = UDF_I(inode);
  89         pos = udf_block_map(inode, 0);
  90
  91         down_read(&iinfo->i_data_sem);
  92         if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
  93                 symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
  94         } else {
  95                 bh = sb_bread(inode->i_sb, pos);
  96
  97                 if (!bh) {
  98                         err = -EIO;
  99                         goto out_unlock_inode;
 100                 }
 101
 102                 symlink = bh->b_data;
 103         }
 104
 105         udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
 106         brelse(bh);
 107
 108         up_read(&iinfo->i_data_sem);
 109         SetPageUptodate(page);
 110         kunmap(page);
 111         unlock_page(page);
 112         return 0;
 113
 114 out_unlock_inode:
 115         up_read(&iinfo->i_data_sem);
 116         SetPageError(page);
 117 out_unmap:
 118         kunmap(page);
 119         unlock_page(page);
 120         return err;
 121 }
 122
 123 /*
 124  * symlinks can't do much...
 125  */
 126 const struct address_space_operations udf_symlink_aops = {
 127         .readpage               = udf_symlink_filler,
 128 };