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Signed-off-by: Phillip Lougher <[email protected]>
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Phillip Lougher
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Jan 5, 2009
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/* | ||
* Squashfs - a compressed read only filesystem for Linux | ||
* | ||
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | ||
* Phillip Lougher <[email protected]> | ||
* | ||
* This program is free software; you can redistribute it and/or | ||
* modify it under the terms of the GNU General Public License | ||
* as published by the Free Software Foundation; either version 2, | ||
* or (at your option) any later version. | ||
* | ||
* This program is distributed in the hope that it will be useful, | ||
* but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
* GNU General Public License for more details. | ||
* | ||
* You should have received a copy of the GNU General Public License | ||
* along with this program; if not, write to the Free Software | ||
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | ||
* | ||
* block.c | ||
*/ | ||
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/* | ||
* This file implements the low-level routines to read and decompress | ||
* datablocks and metadata blocks. | ||
*/ | ||
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#include <linux/fs.h> | ||
#include <linux/vfs.h> | ||
#include <linux/slab.h> | ||
#include <linux/mutex.h> | ||
#include <linux/string.h> | ||
#include <linux/buffer_head.h> | ||
#include <linux/zlib.h> | ||
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#include "squashfs_fs.h" | ||
#include "squashfs_fs_sb.h" | ||
#include "squashfs_fs_i.h" | ||
#include "squashfs.h" | ||
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/* | ||
* Read the metadata block length, this is stored in the first two | ||
* bytes of the metadata block. | ||
*/ | ||
static struct buffer_head *get_block_length(struct super_block *sb, | ||
u64 *cur_index, int *offset, int *length) | ||
{ | ||
struct squashfs_sb_info *msblk = sb->s_fs_info; | ||
struct buffer_head *bh; | ||
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bh = sb_bread(sb, *cur_index); | ||
if (bh == NULL) | ||
return NULL; | ||
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if (msblk->devblksize - *offset == 1) { | ||
*length = (unsigned char) bh->b_data[*offset]; | ||
put_bh(bh); | ||
bh = sb_bread(sb, ++(*cur_index)); | ||
if (bh == NULL) | ||
return NULL; | ||
*length |= (unsigned char) bh->b_data[0] << 8; | ||
*offset = 1; | ||
} else { | ||
*length = (unsigned char) bh->b_data[*offset] | | ||
(unsigned char) bh->b_data[*offset + 1] << 8; | ||
*offset += 2; | ||
} | ||
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return bh; | ||
} | ||
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/* | ||
* Read and decompress a metadata block or datablock. Length is non-zero | ||
* if a datablock is being read (the size is stored elsewhere in the | ||
* filesystem), otherwise the length is obtained from the first two bytes of | ||
* the metadata block. A bit in the length field indicates if the block | ||
* is stored uncompressed in the filesystem (usually because compression | ||
* generated a larger block - this does occasionally happen with zlib). | ||
*/ | ||
int squashfs_read_data(struct super_block *sb, void **buffer, u64 index, | ||
int length, u64 *next_index, int srclength) | ||
{ | ||
struct squashfs_sb_info *msblk = sb->s_fs_info; | ||
struct buffer_head **bh; | ||
int offset = index & ((1 << msblk->devblksize_log2) - 1); | ||
u64 cur_index = index >> msblk->devblksize_log2; | ||
int bytes, compressed, b = 0, k = 0, page = 0, avail; | ||
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bh = kcalloc((msblk->block_size >> msblk->devblksize_log2) + 1, | ||
sizeof(*bh), GFP_KERNEL); | ||
if (bh == NULL) | ||
return -ENOMEM; | ||
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if (length) { | ||
/* | ||
* Datablock. | ||
*/ | ||
bytes = -offset; | ||
compressed = SQUASHFS_COMPRESSED_BLOCK(length); | ||
length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); | ||
if (next_index) | ||
*next_index = index + length; | ||
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TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", | ||
index, compressed ? "" : "un", length, srclength); | ||
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if (length < 0 || length > srclength || | ||
(index + length) > msblk->bytes_used) | ||
goto read_failure; | ||
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for (b = 0; bytes < length; b++, cur_index++) { | ||
bh[b] = sb_getblk(sb, cur_index); | ||
if (bh[b] == NULL) | ||
goto block_release; | ||
bytes += msblk->devblksize; | ||
} | ||
ll_rw_block(READ, b, bh); | ||
} else { | ||
/* | ||
* Metadata block. | ||
*/ | ||
if ((index + 2) > msblk->bytes_used) | ||
goto read_failure; | ||
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bh[0] = get_block_length(sb, &cur_index, &offset, &length); | ||
if (bh[0] == NULL) | ||
goto read_failure; | ||
b = 1; | ||
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bytes = msblk->devblksize - offset; | ||
compressed = SQUASHFS_COMPRESSED(length); | ||
length = SQUASHFS_COMPRESSED_SIZE(length); | ||
if (next_index) | ||
*next_index = index + length + 2; | ||
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TRACE("Block @ 0x%llx, %scompressed size %d\n", index, | ||
compressed ? "" : "un", length); | ||
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if (length < 0 || length > srclength || | ||
(index + length) > msblk->bytes_used) | ||
goto block_release; | ||
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for (; bytes < length; b++) { | ||
bh[b] = sb_getblk(sb, ++cur_index); | ||
if (bh[b] == NULL) | ||
goto block_release; | ||
bytes += msblk->devblksize; | ||
} | ||
ll_rw_block(READ, b - 1, bh + 1); | ||
} | ||
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if (compressed) { | ||
int zlib_err = 0, zlib_init = 0; | ||
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/* | ||
* Uncompress block. | ||
*/ | ||
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mutex_lock(&msblk->read_data_mutex); | ||
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msblk->stream.avail_out = 0; | ||
msblk->stream.avail_in = 0; | ||
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bytes = length; | ||
do { | ||
if (msblk->stream.avail_in == 0 && k < b) { | ||
avail = min(bytes, msblk->devblksize - offset); | ||
bytes -= avail; | ||
wait_on_buffer(bh[k]); | ||
if (!buffer_uptodate(bh[k])) | ||
goto release_mutex; | ||
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if (avail == 0) { | ||
offset = 0; | ||
put_bh(bh[k++]); | ||
continue; | ||
} | ||
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msblk->stream.next_in = bh[k]->b_data + offset; | ||
msblk->stream.avail_in = avail; | ||
offset = 0; | ||
} | ||
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if (msblk->stream.avail_out == 0) { | ||
msblk->stream.next_out = buffer[page++]; | ||
msblk->stream.avail_out = PAGE_CACHE_SIZE; | ||
} | ||
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if (!zlib_init) { | ||
zlib_err = zlib_inflateInit(&msblk->stream); | ||
if (zlib_err != Z_OK) { | ||
ERROR("zlib_inflateInit returned" | ||
" unexpected result 0x%x," | ||
" srclength %d\n", zlib_err, | ||
srclength); | ||
goto release_mutex; | ||
} | ||
zlib_init = 1; | ||
} | ||
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zlib_err = zlib_inflate(&msblk->stream, Z_NO_FLUSH); | ||
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if (msblk->stream.avail_in == 0 && k < b) | ||
put_bh(bh[k++]); | ||
} while (zlib_err == Z_OK); | ||
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if (zlib_err != Z_STREAM_END) { | ||
ERROR("zlib_inflate returned unexpected result" | ||
" 0x%x, srclength %d, avail_in %d," | ||
" avail_out %d\n", zlib_err, srclength, | ||
msblk->stream.avail_in, | ||
msblk->stream.avail_out); | ||
goto release_mutex; | ||
} | ||
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zlib_err = zlib_inflateEnd(&msblk->stream); | ||
if (zlib_err != Z_OK) { | ||
ERROR("zlib_inflateEnd returned unexpected result 0x%x," | ||
" srclength %d\n", zlib_err, srclength); | ||
goto release_mutex; | ||
} | ||
length = msblk->stream.total_out; | ||
mutex_unlock(&msblk->read_data_mutex); | ||
} else { | ||
/* | ||
* Block is uncompressed. | ||
*/ | ||
int i, in, pg_offset = 0; | ||
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for (i = 0; i < b; i++) { | ||
wait_on_buffer(bh[i]); | ||
if (!buffer_uptodate(bh[i])) | ||
goto block_release; | ||
} | ||
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for (bytes = length; k < b; k++) { | ||
in = min(bytes, msblk->devblksize - offset); | ||
bytes -= in; | ||
while (in) { | ||
if (pg_offset == PAGE_CACHE_SIZE) { | ||
page++; | ||
pg_offset = 0; | ||
} | ||
avail = min_t(int, in, PAGE_CACHE_SIZE - | ||
pg_offset); | ||
memcpy(buffer[page] + pg_offset, | ||
bh[k]->b_data + offset, avail); | ||
in -= avail; | ||
pg_offset += avail; | ||
offset += avail; | ||
} | ||
offset = 0; | ||
put_bh(bh[k]); | ||
} | ||
} | ||
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kfree(bh); | ||
return length; | ||
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release_mutex: | ||
mutex_unlock(&msblk->read_data_mutex); | ||
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block_release: | ||
for (; k < b; k++) | ||
put_bh(bh[k]); | ||
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read_failure: | ||
ERROR("sb_bread failed reading block 0x%llx\n", cur_index); | ||
kfree(bh); | ||
return -EIO; | ||
} |