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