drm/i915|intel-gtt: consolidate intel-gtt.h headers
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / squashfs / block.c
blob653c030eb840db0757df698745beca793ce03bf5
1 /*
2 * Squashfs - a compressed read only filesystem for Linux
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@lougher.demon.co.uk>
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.
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.
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.
21 * block.c
25 * This file implements the low-level routines to read and decompress
26 * datablocks and metadata blocks.
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>
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"
42 * Read the metadata block length, this is stored in the first two
43 * bytes of the metadata block.
45 static struct buffer_head *get_block_length(struct super_block *sb,
46 u64 *cur_index, int *offset, int *length)
48 struct squashfs_sb_info *msblk = sb->s_fs_info;
49 struct buffer_head *bh;
51 bh = sb_bread(sb, *cur_index);
52 if (bh == NULL)
53 return NULL;
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;
69 return bh;
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).
81 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
82 int length, u64 *next_index, int srclength, int pages)
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;
90 bh = kcalloc(((srclength + msblk->devblksize - 1)
91 >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
92 if (bh == NULL)
93 return -ENOMEM;
95 if (length) {
97 * Datablock.
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;
105 TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
106 index, compressed ? "" : "un", length, srclength);
108 if (length < 0 || length > srclength ||
109 (index + length) > msblk->bytes_used)
110 goto read_failure;
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;
118 ll_rw_block(READ, b, bh);
119 } else {
121 * Metadata block.
123 if ((index + 2) > msblk->bytes_used)
124 goto read_failure;
126 bh[0] = get_block_length(sb, &cur_index, &offset, &length);
127 if (bh[0] == NULL)
128 goto read_failure;
129 b = 1;
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;
137 TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
138 compressed ? "" : "un", length);
140 if (length < 0 || length > srclength ||
141 (index + length) > msblk->bytes_used)
142 goto block_release;
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;
150 ll_rw_block(READ, b - 1, bh + 1);
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 {
160 * Block is uncompressed.
162 int i, in, pg_offset = 0;
164 for (i = 0; i < b; i++) {
165 wait_on_buffer(bh[i]);
166 if (!buffer_uptodate(bh[i]))
167 goto block_release;
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;
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;
186 offset = 0;
187 put_bh(bh[k]);
191 kfree(bh);
192 return length;
194 block_release:
195 for (; k < b; k++)
196 put_bh(bh[k]);
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;