source: src/linux/universal/linux-4.9/fs/squashfs/dir.c @ 31630

Last change on this file since 31630 was 31630, checked in by brainslayer, 6 weeks ago

new fs is compatible with standard squashfs, just smaller

File size: 5.9 KB
Line 
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        unsigned int size;
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                size = le32_to_cpu(dir_index.size) + 1;
86
87                /* size should never be larger than SQUASHFS_NAME_LEN */
88                if (size > SQUASHFS_NAME_LEN)
89                        break;
90
91                err = squashfs_read_metadata(sb, NULL, &index_start,
92                                &index_offset, size);
93                if (err < 0)
94                        break;
95
96                length = index;
97                *next_block = le32_to_cpu(dir_index.start_block) +
98                                        msblk->directory_table;
99        }
100
101        *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
102
103        /*
104         * Translate back from internal f_pos to external f_pos.
105         */
106        return length + 3;
107}
108
109
110static int squashfs_readdir(struct file *file, struct dir_context *ctx)
111{
112        struct inode *inode = file_inode(file);
113        struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
114        u64 block = squashfs_i(inode)->start + msblk->directory_table;
115        int offset = squashfs_i(inode)->offset, length, err;
116        unsigned int inode_number, dir_count, size, type;
117        struct squashfs_dir_header dirh;
118        struct squashfs_dir_entry *dire;
119
120        TRACE("Entered squashfs_readdir [%llx:%x]\n", block, offset);
121
122        dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
123        if (dire == NULL) {
124                ERROR("Failed to allocate squashfs_dir_entry\n");
125                goto finish;
126        }
127
128        /*
129         * Return "." and  ".." entries as the first two filenames in the
130         * directory.  To maximise compression these two entries are not
131         * stored in the directory, and so we invent them here.
132         *
133         * It also means that the external f_pos is offset by 3 from the
134         * on-disk directory f_pos.
135         */
136        while (ctx->pos < 3) {
137                char *name;
138                int i_ino;
139
140                if (ctx->pos == 0) {
141                        name = ".";
142                        size = 1;
143                        i_ino = inode->i_ino;
144                } else {
145                        name = "..";
146                        size = 2;
147                        i_ino = squashfs_i(inode)->parent;
148                }
149
150                if (!dir_emit(ctx, name, size, i_ino,
151                                squashfs_filetype_table[1]))
152                        goto finish;
153
154                ctx->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                                ctx->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 (ctx->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                        if (type > SQUASHFS_MAX_DIR_TYPE)
210                                goto failed_read;
211
212                        if (!dir_emit(ctx, dire->name, size,
213                                        inode_number,
214                                        squashfs_filetype_table[type]))
215                                goto finish;
216
217                        ctx->pos = length;
218                }
219        }
220
221finish:
222        kfree(dire);
223        return 0;
224
225failed_read:
226        ERROR("Unable to read directory block [%llx:%x]\n", block, offset);
227        kfree(dire);
228        return 0;
229}
230
231
232const struct file_operations squashfs_dir_ops = {
233        .read = generic_read_dir,
234        .iterate_shared = squashfs_readdir,
235        .llseek = generic_file_llseek,
236};
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