fs/squashfs/dir.c

   1 /*
   2  * Squashfs - a compressed read only filesystem for Linux
   3  *
   4  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   5  * Phillip Lougher <phillip@lougher.demon.co.uk>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2,
  10  * or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20  *
  21  * dir.c
  22  */
  23
  24 /*
  25  * This file implements code to read directories from disk.
  26  *
  27  * See namei.c for a description of directory organisation on disk.
  28  */
  29
  30 #include <linux/fs.h>
  31 #include <linux/vfs.h>
  32 #include <linux/slab.h>
  33 #include <linux/zlib.h>
  34
  35 #include "squashfs_fs.h"
  36 #include "squashfs_fs_sb.h"
  37 #include "squashfs_fs_i.h"
  38 #include "squashfs.h"
  39
  40 static const unsigned char squashfs_filetype_table[] = {
  41         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
  42 };
  43
  44 /*
  45  * Lookup offset (f_pos) in the directory index, returning the
  46  * metadata block containing it.
  47  *
  48  * If we get an error reading the index then return the part of the index
  49  * (if any) we have managed to read - the index isn't essential, just
  50  * quicker.
  51  */
  52 static int get_dir_index_using_offset(struct super_block *sb,
  53         u64 *next_block, int *next_offset, u64 index_start, int index_offset,
  54         int i_count, u64 f_pos)
  55 {
  56         struct squashfs_sb_info *msblk = sb->s_fs_info;
  57         int err, i, index, length = 0;
  58         struct squashfs_dir_index dir_index;
  59
  60         TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
  61                                         i_count, f_pos);
  62
  63         /*
  64          * Translate from external f_pos to the internal f_pos.  This
  65          * is offset by 3 because we invent "." and ".." entries which are
  66          * not actually stored in the directory.
  67          */
  68         if (f_pos < 3)
  69                 return f_pos;
  70         f_pos -= 3;
  71
  72         for (i = 0; i < i_count; i++) {
  73                 err = squashfs_read_metadata(sb, &dir_index, &index_start,
  74                                 &index_offset, sizeof(dir_index));
  75                 if (err < 0)
  76                         break;
  77
  78                 index = le32_to_cpu(dir_index.index);
  79                 if (index > f_pos)
  80                         /*
  81                          * Found the index we're looking for.
  82                          */
  83                         break;
  84
  85                 err = squashfs_read_metadata(sb, NULL, &index_start,
  86                                 &index_offset, le32_to_cpu(dir_index.size) + 1);
  87                 if (err < 0)
  88                         break;
  89
  90                 length = index;
  91                 *next_block = le32_to_cpu(dir_index.start_block) +
  92                                         msblk->directory_table;
  93         }
  94
  95         *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
  96
  97         /*
  98          * Translate back from internal f_pos to external f_pos.
  99          */
 100         return length + 3;
 101 }
 102
 103
 104 static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir)
 105 {
 106         struct inode *inode = file->f_dentry->d_inode;
 107         struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
 108         u64 block = squashfs_i(inode)->start + msblk->directory_table;
 109         int offset = squashfs_i(inode)->offset, length = 0, dir_count, size,
 110                                 type, err;
 111         unsigned int inode_number;
 112         struct squashfs_dir_header dirh;
 113         struct squashfs_dir_entry *dire;
 114
 115         TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
 116
 117         dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
 118         if (dire == NULL) {
 119                 ERROR("Failed to allocate squashfs_dir_entry\n");
 120                 goto finish;
 121         }
 122
 123         /*
 124          * Return "." and  ".." entries as the first two filenames in the
 125          * directory.  To maximise compression these two entries are not
 126          * stored in the directory, and so we invent them here.
 127          *
 128          * It also means that the external f_pos is offset by 3 from the
 129          * on-disk directory f_pos.
 130          */
 131         while (file->f_pos < 3) {
 132                 char *name;
 133                 int i_ino;
 134
 135                 if (file->f_pos == 0) {
 136                         name = ".";
 137                         size = 1;
 138                         i_ino = inode->i_ino;
 139                 } else {
 140                         name = "..";
 141                         size = 2;
 142                         i_ino = squashfs_i(inode)->parent;
 143                 }
 144
 145                 TRACE("Calling filldir(%p, %s, %d, %lld, %d, %d)\n",
 146                                 dirent, name, size, file->f_pos, i_ino,
 147                                 squashfs_filetype_table[1]);
 148
 149                 if (filldir(dirent, name, size, file->f_pos, i_ino,
 150                                 squashfs_filetype_table[1]) < 0) {
 151                                 TRACE("Filldir returned less than 0\n");
 152                         goto finish;
 153                 }
 154
 155                 file->f_pos += size;
 156         }
 157
 158         length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
 159                                 squashfs_i(inode)->dir_idx_start,
 160                                 squashfs_i(inode)->dir_idx_offset,
 161                                 squashfs_i(inode)->dir_idx_cnt,
 162                                 file->f_pos);
 163
 164         while (length < i_size_read(inode)) {
 165                 /*
 166                  * Read directory header
 167                  */
 168                 err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
 169                                         &offset, sizeof(dirh));
 170                 if (err < 0)
 171                         goto failed_read;
 172
 173                 length += sizeof(dirh);
 174
 175                 dir_count = le32_to_cpu(dirh.count) + 1;
 176                 while (dir_count--) {
 177                         /*
 178                          * Read directory entry.
 179                          */
 180                         err = squashfs_read_metadata(inode->i_sb, dire, &block,
 181                                         &offset, sizeof(*dire));
 182                         if (err < 0)
 183                                 goto failed_read;
 184
 185                         size = le16_to_cpu(dire->size) + 1;
 186
 187                         err = squashfs_read_metadata(inode->i_sb, dire->name,
 188                                         &block, &offset, size);
 189                         if (err < 0)
 190                                 goto failed_read;
 191
 192                         length += sizeof(*dire) + size;
 193
 194                         if (file->f_pos >= length)
 195                                 continue;
 196
 197                         dire->name[size] = '\0';
 198                         inode_number = le32_to_cpu(dirh.inode_number) +
 199                                 ((short) le16_to_cpu(dire->inode_number));
 200                         type = le16_to_cpu(dire->type);
 201
 202                         TRACE("Calling filldir(%p, %s, %d, %lld, %x:%x, %d, %d)"
 203                                         "\n", dirent, dire->name, size,
 204                                         file->f_pos,
 205                                         le32_to_cpu(dirh.start_block),
 206                                         le16_to_cpu(dire->offset),
 207                                         inode_number,
 208                                         squashfs_filetype_table[type]);
 209
 210                         if (filldir(dirent, dire->name, size, file->f_pos,
 211                                         inode_number,
 212                                         squashfs_filetype_table[type]) < 0) {
 213                                 TRACE("Filldir returned less than 0\n");
 214                                 goto finish;
 215                         }
 216
 217                         file->f_pos = length;
 218                 }
 219         }
 220
 221 finish:
 222         kfree(dire);
 223         return 0;
 224
 225 failed_read:
 226         ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
 227         kfree(dire);
 228         return 0;
 229 }
 230
 231
 232 const struct file_operations squashfs_dir_ops = {
 233         .read = generic_read_dir,
 234         .readdir = squashfs_readdir
 235 };