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 */
46static 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 */
82int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
83			int length, u64 *next_index, int srclength)
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) {
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_NO_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 returned unexpected result"
212				" 0x%x, srclength %d, avail_in %d,"
213				" avail_out %d\n", zlib_err, srclength,
214				msblk->stream.avail_in,
215				msblk->stream.avail_out);
216			goto release_mutex;
217		}
218
219		zlib_err = zlib_inflateEnd(&msblk->stream);
220		if (zlib_err != Z_OK) {
221			ERROR("zlib_inflateEnd returned unexpected result 0x%x,"
222				" srclength %d\n", zlib_err, srclength);
223			goto release_mutex;
224		}
225		length = msblk->stream.total_out;
226		mutex_unlock(&msblk->read_data_mutex);
227	} else {
228		/*
229		 * Block is uncompressed.
230		 */
231		int i, in, pg_offset = 0;
232
233		for (i = 0; i < b; i++) {
234			wait_on_buffer(bh[i]);
235			if (!buffer_uptodate(bh[i]))
236				goto block_release;
237		}
238
239		for (bytes = length; k < b; k++) {
240			in = min(bytes, msblk->devblksize - offset);
241			bytes -= in;
242			while (in) {
243				if (pg_offset == PAGE_CACHE_SIZE) {
244					page++;
245					pg_offset = 0;
246				}
247				avail = min_t(int, in, PAGE_CACHE_SIZE -
248						pg_offset);
249				memcpy(buffer[page] + pg_offset,
250						bh[k]->b_data + offset, avail);
251				in -= avail;
252				pg_offset += avail;
253				offset += avail;
254			}
255			offset = 0;
256			put_bh(bh[k]);
257		}
258	}
259
260	kfree(bh);
261	return length;
262
263release_mutex:
264	mutex_unlock(&msblk->read_data_mutex);
265
266block_release:
267	for (; k < b; k++)
268		put_bh(bh[k]);
269
270read_failure:
271	ERROR("sb_bread failed reading block 0x%llx\n", cur_index);
272	kfree(bh);
273	return -EIO;
274}
275