linux/fs/udf/symlink.c
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   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
  33static 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
  78static 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
 112out:
 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 */
 123const struct address_space_operations udf_symlink_aops = {
 124        .readpage               = udf_symlink_filler,
 125};
 126
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