566b0eaed868df557a7e05061cd31b0f160a2b54
[linux-2.6.git] / 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 };