Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6
[linux-2.6] / 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/mutex.h>
33 #include <linux/string.h>
34 #include <linux/buffer_head.h>
35 #include <linux/zlib.h>
36
37 #include "squashfs_fs.h"
38 #include "squashfs_fs_sb.h"
39 #include "squashfs_fs_i.h"
40 #include "squashfs.h"
41
42 /*
43  * Read the metadata block length, this is stored in the first two
44  * bytes of the metadata block.
45  */
46 static struct buffer_head *get_block_length(struct super_block *sb,
47                         u64 *cur_index, int *offset, int *length)
48 {
49         struct squashfs_sb_info *msblk = sb->s_fs_info;
50         struct buffer_head *bh;
51
52         bh = sb_bread(sb, *cur_index);
53         if (bh == NULL)
54                 return NULL;
55
56         if (msblk->devblksize - *offset == 1) {
57                 *length = (unsigned char) bh->b_data[*offset];
58                 put_bh(bh);
59                 bh = sb_bread(sb, ++(*cur_index));
60                 if (bh == NULL)
61                         return NULL;
62                 *length |= (unsigned char) bh->b_data[0] << 8;
63                 *offset = 1;
64         } else {
65                 *length = (unsigned char) bh->b_data[*offset] |
66                         (unsigned char) bh->b_data[*offset + 1] << 8;
67                 *offset += 2;
68         }
69
70         return bh;
71 }
72
73
74 /*
75  * Read and decompress a metadata block or datablock.  Length is non-zero
76  * if a datablock is being read (the size is stored elsewhere in the
77  * filesystem), otherwise the length is obtained from the first two bytes of
78  * the metadata block.  A bit in the length field indicates if the block
79  * is stored uncompressed in the filesystem (usually because compression
80  * generated a larger block - this does occasionally happen with zlib).
81  */
82 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
83                         int length, u64 *next_index, int srclength, int pages)
84 {
85         struct squashfs_sb_info *msblk = sb->s_fs_info;
86         struct buffer_head **bh;
87         int offset = index & ((1 << msblk->devblksize_log2) - 1);
88         u64 cur_index = index >> msblk->devblksize_log2;
89         int bytes, compressed, b = 0, k = 0, page = 0, avail;
90
91
92         bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1,
93                                 sizeof(*bh), GFP_KERNEL);
94         if (bh == NULL)
95                 return -ENOMEM;
96
97         if (length) {
98                 /*
99                  * Datablock.
100                  */
101                 bytes = -offset;
102                 compressed = SQUASHFS_COMPRESSED_BLOCK(length);
103                 length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
104                 if (next_index)
105                         *next_index = index + length;
106
107                 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
108                         index, compressed ? "" : "un", length, srclength);
109
110                 if (length < 0 || length > srclength ||
111                                 (index + length) > msblk->bytes_used)
112                         goto read_failure;
113
114                 for (b = 0; bytes < length; b++, cur_index++) {
115                         bh[b] = sb_getblk(sb, cur_index);
116                         if (bh[b] == NULL)
117                                 goto block_release;
118                         bytes += msblk->devblksize;
119                 }
120                 ll_rw_block(READ, b, bh);
121         } else {
122                 /*
123                  * Metadata block.
124                  */
125                 if ((index + 2) > msblk->bytes_used)
126                         goto read_failure;
127
128                 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
129                 if (bh[0] == NULL)
130                         goto read_failure;
131                 b = 1;
132
133                 bytes = msblk->devblksize - offset;
134                 compressed = SQUASHFS_COMPRESSED(length);
135                 length = SQUASHFS_COMPRESSED_SIZE(length);
136                 if (next_index)
137                         *next_index = index + length + 2;
138
139                 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
140                                 compressed ? "" : "un", length);
141
142                 if (length < 0 || length > srclength ||
143                                         (index + length) > msblk->bytes_used)
144                         goto block_release;
145
146                 for (; bytes < length; b++) {
147                         bh[b] = sb_getblk(sb, ++cur_index);
148                         if (bh[b] == NULL)
149                                 goto block_release;
150                         bytes += msblk->devblksize;
151                 }
152                 ll_rw_block(READ, b - 1, bh + 1);
153         }
154
155         if (compressed) {
156                 int zlib_err = 0, zlib_init = 0;
157
158                 /*
159                  * Uncompress block.
160                  */
161
162                 mutex_lock(&msblk->read_data_mutex);
163
164                 msblk->stream.avail_out = 0;
165                 msblk->stream.avail_in = 0;
166
167                 bytes = length;
168                 do {
169                         if (msblk->stream.avail_in == 0 && k < b) {
170                                 avail = min(bytes, msblk->devblksize - offset);
171                                 bytes -= avail;
172                                 wait_on_buffer(bh[k]);
173                                 if (!buffer_uptodate(bh[k]))
174                                         goto release_mutex;
175
176                                 if (avail == 0) {
177                                         offset = 0;
178                                         put_bh(bh[k++]);
179                                         continue;
180                                 }
181
182                                 msblk->stream.next_in = bh[k]->b_data + offset;
183                                 msblk->stream.avail_in = avail;
184                                 offset = 0;
185                         }
186
187                         if (msblk->stream.avail_out == 0 && page < pages) {
188                                 msblk->stream.next_out = buffer[page++];
189                                 msblk->stream.avail_out = PAGE_CACHE_SIZE;
190                         }
191
192                         if (!zlib_init) {
193                                 zlib_err = zlib_inflateInit(&msblk->stream);
194                                 if (zlib_err != Z_OK) {
195                                         ERROR("zlib_inflateInit returned"
196                                                 " unexpected result 0x%x,"
197                                                 " srclength %d\n", zlib_err,
198                                                 srclength);
199                                         goto release_mutex;
200                                 }
201                                 zlib_init = 1;
202                         }
203
204                         zlib_err = zlib_inflate(&msblk->stream, Z_SYNC_FLUSH);
205
206                         if (msblk->stream.avail_in == 0 && k < b)
207                                 put_bh(bh[k++]);
208                 } while (zlib_err == Z_OK);
209
210                 if (zlib_err != Z_STREAM_END) {
211                         ERROR("zlib_inflate error, data probably corrupt\n");
212                         goto release_mutex;
213                 }
214
215                 zlib_err = zlib_inflateEnd(&msblk->stream);
216                 if (zlib_err != Z_OK) {
217                         ERROR("zlib_inflate error, data probably corrupt\n");
218                         goto release_mutex;
219                 }
220                 length = msblk->stream.total_out;
221                 mutex_unlock(&msblk->read_data_mutex);
222         } else {
223                 /*
224                  * Block is uncompressed.
225                  */
226                 int i, in, pg_offset = 0;
227
228                 for (i = 0; i < b; i++) {
229                         wait_on_buffer(bh[i]);
230                         if (!buffer_uptodate(bh[i]))
231                                 goto block_release;
232                 }
233
234                 for (bytes = length; k < b; k++) {
235                         in = min(bytes, msblk->devblksize - offset);
236                         bytes -= in;
237                         while (in) {
238                                 if (pg_offset == PAGE_CACHE_SIZE) {
239                                         page++;
240                                         pg_offset = 0;
241                                 }
242                                 avail = min_t(int, in, PAGE_CACHE_SIZE -
243                                                 pg_offset);
244                                 memcpy(buffer[page] + pg_offset,
245                                                 bh[k]->b_data + offset, avail);
246                                 in -= avail;
247                                 pg_offset += avail;
248                                 offset += avail;
249                         }
250                         offset = 0;
251                         put_bh(bh[k]);
252                 }
253         }
254
255         kfree(bh);
256         return length;
257
258 release_mutex:
259         mutex_unlock(&msblk->read_data_mutex);
260
261 block_release:
262         for (; k < b; k++)
263                 put_bh(bh[k]);
264
265 read_failure:
266         ERROR("squashfs_read_data failed to read block 0x%llx\n",
267                                         (unsigned long long) index);
268         kfree(bh);
269         return -EIO;
270 }