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 * fragment.c
22 */
23
24 /*
25 * This file implements code to handle compressed fragments (tail-end packed
26 * datablocks).
27 *
28 * Regular files contain a fragment index which is mapped to a fragment
29 * location on disk and compressed size using a fragment lookup table.
30 * Like everything in Squashfs this fragment lookup table is itself stored
31 * compressed into metadata blocks. A second index table is used to locate
32 * these. This second index table for speed of access (and because it
33 * is small) is read at mount time and cached in memory.
34 */
35
36 #include <linux/fs.h>
37 #include <linux/vfs.h>
38 #include <linux/slab.h>
39 #include <linux/zlib.h>
40
41 #include "squashfs_fs.h"
42 #include "squashfs_fs_sb.h"
43 #include "squashfs_fs_i.h"
44 #include "squashfs.h"
45
46 /*
47 * Look-up fragment using the fragment index table. Return the on disk
48 * location of the fragment and its compressed size
49 */
squashfs_frag_lookup(struct super_block * sb,unsigned int fragment,u64 * fragment_block)50 int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
51 u64 *fragment_block)
52 {
53 struct squashfs_sb_info *msblk = sb->s_fs_info;
54 int block = SQUASHFS_FRAGMENT_INDEX(fragment);
55 int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
56 u64 start_block = le64_to_cpu(msblk->fragment_index[block]);
57 struct squashfs_fragment_entry fragment_entry;
58 int size;
59
60 size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
61 &offset, sizeof(fragment_entry));
62 if (size < 0)
63 return size;
64
65 *fragment_block = le64_to_cpu(fragment_entry.start_block);
66 size = le32_to_cpu(fragment_entry.size);
67
68 return size;
69 }
70
71
72 /*
73 * Read the uncompressed fragment lookup table indexes off disk into memory
74 */
squashfs_read_fragment_index_table(struct super_block * sb,u64 fragment_table_start,unsigned int fragments)75 __le64 *squashfs_read_fragment_index_table(struct super_block *sb,
76 u64 fragment_table_start, unsigned int fragments)
77 {
78 unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
79 __le64 *fragment_index;
80 int err;
81
82 /* Allocate fragment lookup table indexes */
83 fragment_index = kmalloc(length, GFP_KERNEL);
84 if (fragment_index == NULL) {
85 ERROR("Failed to allocate fragment index table\n");
86 return ERR_PTR(-ENOMEM);
87 }
88
89 err = squashfs_read_table(sb, fragment_index, fragment_table_start,
90 length);
91 if (err < 0) {
92 ERROR("unable to read fragment index table\n");
93 kfree(fragment_index);
94 return ERR_PTR(err);
95 }
96
97 return fragment_index;
98 }
99