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 };
236
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