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07972dde PL |
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 | }; |