1cb0d81b164b5cf02ff67ceedc8275838b6db868
[pandora-kernel.git] / fs / squashfs / block.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  * block.c
22  */
23
24 /*
25  * This file implements the low-level routines to read and decompress
26  * datablocks and metadata blocks.
27  */
28
29 #include <linux/fs.h>
30 #include <linux/vfs.h>
31 #include <linux/slab.h>
32 #include <linux/string.h>
33 #include <linux/buffer_head.h>
34
35 #include "squashfs_fs.h"
36 #include "squashfs_fs_sb.h"
37 #include "squashfs_fs_i.h"
38 #include "squashfs.h"
39 #include "decompressor.h"
40
41 /*
42  * Read the metadata block length, this is stored in the first two
43  * bytes of the metadata block.
44  */
45 static struct buffer_head *get_block_length(struct super_block *sb,
46                         u64 *cur_index, int *offset, int *length)
47 {
48         struct squashfs_sb_info *msblk = sb->s_fs_info;
49         struct buffer_head *bh;
50
51         bh = sb_bread(sb, *cur_index);
52         if (bh == NULL)
53                 return NULL;
54
55         if (msblk->devblksize - *offset == 1) {
56                 *length = (unsigned char) bh->b_data[*offset];
57                 put_bh(bh);
58                 bh = sb_bread(sb, ++(*cur_index));
59                 if (bh == NULL)
60                         return NULL;
61                 *length |= (unsigned char) bh->b_data[0] << 8;
62                 *offset = 1;
63         } else {
64                 *length = (unsigned char) bh->b_data[*offset] |
65                         (unsigned char) bh->b_data[*offset + 1] << 8;
66                 *offset += 2;
67         }
68
69         return bh;
70 }
71
72
73 /*
74  * Read and decompress a metadata block or datablock.  Length is non-zero
75  * if a datablock is being read (the size is stored elsewhere in the
76  * filesystem), otherwise the length is obtained from the first two bytes of
77  * the metadata block.  A bit in the length field indicates if the block
78  * is stored uncompressed in the filesystem (usually because compression
79  * generated a larger block - this does occasionally happen with zlib).
80  */
81 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
82                         int length, u64 *next_index, int srclength, int pages)
83 {
84         struct squashfs_sb_info *msblk = sb->s_fs_info;
85         struct buffer_head **bh;
86         int offset = index & ((1 << msblk->devblksize_log2) - 1);
87         u64 cur_index = index >> msblk->devblksize_log2;
88         int bytes, compressed, b = 0, k = 0, page = 0, avail;
89
90
91         bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1,
92                                 sizeof(*bh), GFP_KERNEL);
93         if (bh == NULL)
94                 return -ENOMEM;
95
96         if (length) {
97                 /*
98                  * Datablock.
99                  */
100                 bytes = -offset;
101                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
102                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
103                 if (next_index)
104                         *next_index = index + length;
105
106                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
107                         index, compressed ? "" : "un", length, srclength);
108
109                 if (length < 0 || length > srclength ||
110                                 (index + length) > msblk->bytes_used)
111                         goto read_failure;
112
113                 for (b = 0; bytes < length; b++, cur_index++) {
114                         bh[b] = sb_getblk(sb, cur_index);
115                         if (bh[b] == NULL)
116                                 goto block_release;
117                         bytes += msblk->devblksize;
118                 }
119                 ll_rw_block(READ, b, bh);
120         } else {
121                 /*
122                  * Metadata block.
123                  */
124                 if ((index + 2) > msblk->bytes_used)
125                         goto read_failure;
126
127                 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
128                 if (bh[0] == NULL)
129                         goto read_failure;
130                 b = 1;
131
132                 bytes = msblk->devblksize - offset;
133                 compressed = SQUASHFS_COMPRESSED(length);
134                 length = SQUASHFS_COMPRESSED_SIZE(length);
135                 if (next_index)
136                         *next_index = index + length + 2;
137
138                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
139                                 compressed ? "" : "un", length);
140
141                 if (length < 0 || length > srclength ||
142                                         (index + length) > msblk->bytes_used)
143                         goto block_release;
144
145                 for (; bytes < length; b++) {
146                         bh[b] = sb_getblk(sb, ++cur_index);
147                         if (bh[b] == NULL)
148                                 goto block_release;
149                         bytes += msblk->devblksize;
150                 }
151                 ll_rw_block(READ, b - 1, bh + 1);
152         }
153
154         if (compressed) {
155                 length = squashfs_decompress(msblk, buffer, bh, b, offset,
156                          length, srclength, pages);
157                 if (length < 0)
158                         goto read_failure;
159         } else {
160                 /*
161                  * Block is uncompressed.
162                  */
163                 int i, in, pg_offset = 0;
164
165                 for (i = 0; i < b; i++) {
166                         wait_on_buffer(bh[i]);
167                         if (!buffer_uptodate(bh[i]))
168                                 goto block_release;
169                 }
170
171                 for (bytes = length; k < b; k++) {
172                         in = min(bytes, msblk->devblksize - offset);
173                         bytes -= in;
174                         while (in) {
175                                 if (pg_offset == PAGE_CACHE_SIZE) {
176                                         page++;
177                                         pg_offset = 0;
178                                 }
179                                 avail = min_t(int, in, PAGE_CACHE_SIZE -
180                                                 pg_offset);
181                                 memcpy(buffer[page] + pg_offset,
182                                                 bh[k]->b_data + offset, avail);
183                                 in -= avail;
184                                 pg_offset += avail;
185                                 offset += avail;
186                         }
187                         offset = 0;
188                         put_bh(bh[k]);
189                 }
190         }
191
192         kfree(bh);
193         return length;
194
195 block_release:
196         for (; k < b; k++)
197                 put_bh(bh[k]);
198
199 read_failure:
200         ERROR("squashfs_read_data failed to read block 0x%llx\n",
201                                         (unsigned long long) index);
202         kfree(bh);
203         return -EIO;
204 }