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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 
 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 };
126 

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