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 <linux/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                         /*
  45                          * Symlink points to some place which should be agreed
  46                          * upon between originator and receiver of the media. Ignore.
  47                          */
  48                         if (pc->lengthComponentIdent > 0)
  49                                 break;
  50                         /* Fall through */
  51                 case 2:
  52                         p = to;
  53                         *p++ = '/';
  54                         break;
  55                 case 3:
  56                         memcpy(p, "../", 3);
  57                         p += 3;
  58                         break;
  59                 case 4:
  60                         memcpy(p, "./", 2);
  61                         p += 2;
  62                         /* that would be . - just ignore */
  63                         break;
  64                 case 5:
  65                         p += udf_get_filename(sb, pc->componentIdent, p,
  66                                               pc->lengthComponentIdent);
  67                         *p++ = '/';
  68                         break;
  69                 }
  70                 elen += sizeof(struct pathComponent) + pc->lengthComponentIdent;
  71         }
  72         if (p > to + 1)
  73                 p[-1] = '\0';
  74         else
  75                 p[0] = '\0';
  76 }
  77
  78 static int udf_symlink_filler(struct file *file, struct page *page)
  79 {
  80         struct inode *inode = page->mapping->host;
  81         struct buffer_head *bh = NULL;
  82         unsigned char *symlink;
  83         int err = -EIO;
  84         unsigned char *p = kmap(page);
  85         struct udf_inode_info *iinfo;
  86         uint32_t pos;
  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                         goto out;
  99
 100                 symlink = bh->b_data;
 101         }
 102
 103         udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
 104         brelse(bh);
 105
 106         up_read(&iinfo->i_data_sem);
 107         SetPageUptodate(page);
 108         kunmap(page);
 109         unlock_page(page);
 110         return 0;
 111
 112 out:
 113         up_read(&iinfo->i_data_sem);
 114         SetPageError(page);
 115         kunmap(page);
 116         unlock_page(page);
 117         return err;
 118 }
 119
 120 /*
 121  * symlinks can't do much...
 122  */
 123 const struct address_space_operations udf_symlink_aops = {
 124         .readpage               = udf_symlink_filler,
 125 };