Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/kaber/ipmr-2.6
[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         bh = kcalloc(((srclength + msblk->devblksize - 1)
91                 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
92         if (bh == NULL)
93                 return -ENOMEM;
94
95         if (length) {
96                 /*
97                  * Datablock.
98                  */
99                 bytes = -offset;
100                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
101                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
102                 if (next_index)
103                         *next_index = index + length;
104
105                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
106                         index, compressed ? "" : "un", length, srclength);
107
108                 if (length < 0 || length > srclength ||
109                                 (index + length) > msblk->bytes_used)
110                         goto read_failure;
111
112                 for (b = 0; bytes < length; b++, cur_index++) {
113                         bh[b] = sb_getblk(sb, cur_index);
114                         if (bh[b] == NULL)
115                                 goto block_release;
116                         bytes += msblk->devblksize;
117                 }
118                 ll_rw_block(READ, b, bh);
119         } else {
120                 /*
121                  * Metadata block.
122                  */
123                 if ((index + 2) > msblk->bytes_used)
124                         goto read_failure;
125
126                 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
127                 if (bh[0] == NULL)
128                         goto read_failure;
129                 b = 1;
130
131                 bytes = msblk->devblksize - offset;
132                 compressed = SQUASHFS_COMPRESSED(length);
133                 length = SQUASHFS_COMPRESSED_SIZE(length);
134                 if (next_index)
135                         *next_index = index + length + 2;
136
137                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
138                                 compressed ? "" : "un", length);
139
140                 if (length < 0 || length > srclength ||
141                                         (index + length) > msblk->bytes_used)
142                         goto block_release;
143
144                 for (; bytes < length; b++) {
145                         bh[b] = sb_getblk(sb, ++cur_index);
146                         if (bh[b] == NULL)
147                                 goto block_release;
148                         bytes += msblk->devblksize;
149                 }
150                 ll_rw_block(READ, b - 1, bh + 1);
151         }
152
153         if (compressed) {
154                 length = squashfs_decompress(msblk, buffer, bh, b, offset,
155                          length, srclength, pages);
156                 if (length < 0)
157                         goto read_failure;
158         } else {
159                 /*
160                  * Block is uncompressed.
161                  */
162                 int i, in, pg_offset = 0;
163
164                 for (i = 0; i < b; i++) {
165                         wait_on_buffer(bh[i]);
166                         if (!buffer_uptodate(bh[i]))
167                                 goto block_release;
168                 }
169
170                 for (bytes = length; k < b; k++) {
171                         in = min(bytes, msblk->devblksize - offset);
172                         bytes -= in;
173                         while (in) {
174                                 if (pg_offset == PAGE_CACHE_SIZE) {
175                                         page++;
176                                         pg_offset = 0;
177                                 }
178                                 avail = min_t(int, in, PAGE_CACHE_SIZE -
179                                                 pg_offset);
180                                 memcpy(buffer[page] + pg_offset,
181                                                 bh[k]->b_data + offset, avail);
182                                 in -= avail;
183                                 pg_offset += avail;
184                                 offset += avail;
185                         }
186                         offset = 0;
187                         put_bh(bh[k]);
188                 }
189         }
190
191         kfree(bh);
192         return length;
193
194 block_release:
195         for (; k < b; k++)
196                 put_bh(bh[k]);
197
198 read_failure:
199         ERROR("squashfs_read_data failed to read block 0x%llx\n",
200                                         (unsigned long long) index);
201         kfree(bh);
202         return -EIO;
203 }