linux/fs/squashfs/dir.c
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   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@squashfs.org.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
  34#include "squashfs_fs.h"
  35#include "squashfs_fs_sb.h"
  36#include "squashfs_fs_i.h"
  37#include "squashfs.h"
  38
  39static const unsigned char squashfs_filetype_table[] = {
  40        DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_FIFO, DT_SOCK
  41};
  42
  43/*
  44 * Lookup offset (f_pos) in the directory index, returning the
  45 * metadata block containing it.
  46 *
  47 * If we get an error reading the index then return the part of the index
  48 * (if any) we have managed to read - the index isn't essential, just
  49 * quicker.
  50 */
  51static int get_dir_index_using_offset(struct super_block *sb,
  52        u64 *next_block, int *next_offset, u64 index_start, int index_offset,
  53        int i_count, u64 f_pos)
  54{
  55        struct squashfs_sb_info *msblk = sb->s_fs_info;
  56        int err, i, index, length = 0;
  57        struct squashfs_dir_index dir_index;
  58
  59        TRACE("Entered get_dir_index_using_offset, i_count %d, f_pos %lld\n",
  60                                        i_count, f_pos);
  61
  62        /*
  63         * Translate from external f_pos to the internal f_pos.  This
  64         * is offset by 3 because we invent "." and ".." entries which are
  65         * not actually stored in the directory.
  66         */
  67        if (f_pos <= 3)
  68                return f_pos;
  69        f_pos -= 3;
  70
  71        for (i = 0; i < i_count; i++) {
  72                err = squashfs_read_metadata(sb, &dir_index, &index_start,
  73                                &index_offset, sizeof(dir_index));
  74                if (err < 0)
  75                        break;
  76
  77                index = le32_to_cpu(dir_index.index);
  78                if (index > f_pos)
  79                        /*
  80                         * Found the index we're looking for.
  81                         */
  82                        break;
  83
  84                err = squashfs_read_metadata(sb, NULL, &index_start,
  85                                &index_offset, le32_to_cpu(dir_index.size) + 1);
  86                if (err < 0)
  87                        break;
  88
  89                length = index;
  90                *next_block = le32_to_cpu(dir_index.start_block) +
  91                                        msblk->directory_table;
  92        }
  93
  94        *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
  95
  96        /*
  97         * Translate back from internal f_pos to external f_pos.
  98         */
  99        return length + 3;
 100}
 101
 102
 103static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir)
 104{
 105        struct inode *inode = file->f_dentry->d_inode;
 106        struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
 107        u64 block = squashfs_i(inode)->start + msblk->directory_table;
 108        int offset = squashfs_i(inode)->offset, length, dir_count, size,
 109                                type, err;
 110        unsigned int inode_number;
 111        struct squashfs_dir_header dirh;
 112        struct squashfs_dir_entry *dire;
 113
 114        TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
 115
 116        dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
 117        if (dire == NULL) {
 118                ERROR("Failed to allocate squashfs_dir_entry\n");
 119                goto finish;
 120        }
 121
 122        /*
 123         * Return "." and  ".." entries as the first two filenames in the
 124         * directory.  To maximise compression these two entries are not
 125         * stored in the directory, and so we invent them here.
 126         *
 127         * It also means that the external f_pos is offset by 3 from the
 128         * on-disk directory f_pos.
 129         */
 130        while (file->f_pos < 3) {
 131                char *name;
 132                int i_ino;
 133
 134                if (file->f_pos == 0) {
 135                        name = ".";
 136                        size = 1;
 137                        i_ino = inode->i_ino;
 138                } else {
 139                        name = "..";
 140                        size = 2;
 141                        i_ino = squashfs_i(inode)->parent;
 142                }
 143
 144                TRACE("Calling filldir(%p, %s, %d, %lld, %d, %d)\n",
 145                                dirent, name, size, file->f_pos, i_ino,
 146                                squashfs_filetype_table[1]);
 147
 148                if (filldir(dirent, name, size, file->f_pos, i_ino,
 149                                squashfs_filetype_table[1]) < 0) {
 150                                TRACE("Filldir returned less than 0\n");
 151                        goto finish;
 152                }
 153
 154                file->f_pos += size;
 155        }
 156
 157        length = get_dir_index_using_offset(inode->i_sb, &block, &offset,
 158                                squashfs_i(inode)->dir_idx_start,
 159                                squashfs_i(inode)->dir_idx_offset,
 160                                squashfs_i(inode)->dir_idx_cnt,
 161                                file->f_pos);
 162
 163        while (length < i_size_read(inode)) {
 164                /*
 165                 * Read directory header
 166                 */
 167                err = squashfs_read_metadata(inode->i_sb, &dirh, &block,
 168                                        &offset, sizeof(dirh));
 169                if (err < 0)
 170                        goto failed_read;
 171
 172                length += sizeof(dirh);
 173
 174                dir_count = le32_to_cpu(dirh.count) + 1;
 175
 176                if (dir_count > SQUASHFS_DIR_COUNT)
 177                        goto failed_read;
 178
 179                while (dir_count--) {
 180                        /*
 181                         * Read directory entry.
 182                         */
 183                        err = squashfs_read_metadata(inode->i_sb, dire, &block,
 184                                        &offset, sizeof(*dire));
 185                        if (err < 0)
 186                                goto failed_read;
 187
 188                        size = le16_to_cpu(dire->size) + 1;
 189
 190                        /* size should never be larger than SQUASHFS_NAME_LEN */
 191                        if (size > SQUASHFS_NAME_LEN)
 192                                goto failed_read;
 193
 194                        err = squashfs_read_metadata(inode->i_sb, dire->name,
 195                                        &block, &offset, size);
 196                        if (err < 0)
 197                                goto failed_read;
 198
 199                        length += sizeof(*dire) + size;
 200
 201                        if (file->f_pos >= length)
 202                                continue;
 203
 204                        dire->name[size] = '\0';
 205                        inode_number = le32_to_cpu(dirh.inode_number) +
 206                                ((short) le16_to_cpu(dire->inode_number));
 207                        type = le16_to_cpu(dire->type);
 208
 209                        TRACE("Calling filldir(%p, %s, %d, %lld, %x:%x, %d, %d)"
 210                                        "\n", dirent, dire->name, size,
 211                                        file->f_pos,
 212                                        le32_to_cpu(dirh.start_block),
 213                                        le16_to_cpu(dire->offset),
 214                                        inode_number,
 215                                        squashfs_filetype_table[type]);
 216
 217                        if (filldir(dirent, dire->name, size, file->f_pos,
 218                                        inode_number,
 219                                        squashfs_filetype_table[type]) < 0) {
 220                                TRACE("Filldir returned less than 0\n");
 221                                goto finish;
 222                        }
 223
 224                        file->f_pos = length;
 225                }
 226        }
 227
 228finish:
 229        kfree(dire);
 230        return 0;
 231
 232failed_read:
 233        ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
 234        kfree(dire);
 235        return 0;
 236}
 237
 238
 239const struct file_operations squashfs_dir_ops = {
 240        .read = generic_read_dir,
 241        .readdir = squashfs_readdir,
 242        .llseek = default_llseek,
 243};
 244
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