diff options
Diffstat (limited to 'fs/squashfs/block.c')
| -rw-r--r-- | fs/squashfs/block.c | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c new file mode 100644 index 000000000..0cea9b923 --- /dev/null +++ b/fs/squashfs/block.c @@ -0,0 +1,214 @@ +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + * Phillip Lougher <phillip@squashfs.org.uk> + * + * 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 + */ + +/* + * This file implements the low-level routines to read and decompress + * datablocks and metadata blocks. + */ + +#include <linux/fs.h> +#include <linux/vfs.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/buffer_head.h> + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "squashfs.h" +#include "decompressor.h" +#include "page_actor.h" + +/* + * 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; + + bh = sb_bread(sb, *cur_index); + if (bh == NULL) + return NULL; + + 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; + + if (*offset == msblk->devblksize) { + put_bh(bh); + bh = sb_bread(sb, ++(*cur_index)); + if (bh == NULL) + return NULL; + *offset = 0; + } + } + + return bh; +} + + +/* + * 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 compression + * algorithms). + */ +int squashfs_read_data(struct super_block *sb, u64 index, int length, + u64 *next_index, struct squashfs_page_actor *output) +{ + 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, avail, i; + + bh = kcalloc(((output->length + msblk->devblksize - 1) + >> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL); + if (bh == NULL) + return -ENOMEM; + + if (length) { + /* + * Datablock. + */ + bytes = -offset; + compressed = SQUASHFS_COMPRESSED_BLOCK(length); + length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length); + if (next_index) + *next_index = index + length; + + TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n", + index, compressed ? "" : "un", length, output->length); + + if (length < 0 || length > output->length || + (index + length) > msblk->bytes_used) + goto read_failure; + + 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; + + bh[0] = get_block_length(sb, &cur_index, &offset, &length); + if (bh[0] == NULL) + goto read_failure; + b = 1; + + bytes = msblk->devblksize - offset; + compressed = SQUASHFS_COMPRESSED(length); + length = SQUASHFS_COMPRESSED_SIZE(length); + if (next_index) + *next_index = index + length + 2; + + TRACE("Block @ 0x%llx, %scompressed size %d\n", index, + compressed ? "" : "un", length); + + if (length < 0 || length > output->length || + (index + length) > msblk->bytes_used) + goto block_release; + + 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); + } + + for (i = 0; i < b; i++) { + wait_on_buffer(bh[i]); + if (!buffer_uptodate(bh[i])) + goto block_release; + } + + if (compressed) { + length = squashfs_decompress(msblk, bh, b, offset, length, + output); + if (length < 0) + goto read_failure; + } else { + /* + * Block is uncompressed. + */ + int in, pg_offset = 0; + void *data = squashfs_first_page(output); + + for (bytes = length; k < b; k++) { + in = min(bytes, msblk->devblksize - offset); + bytes -= in; + while (in) { + if (pg_offset == PAGE_CACHE_SIZE) { + data = squashfs_next_page(output); + pg_offset = 0; + } + avail = min_t(int, in, PAGE_CACHE_SIZE - + pg_offset); + memcpy(data + pg_offset, bh[k]->b_data + offset, + avail); + in -= avail; + pg_offset += avail; + offset += avail; + } + offset = 0; + put_bh(bh[k]); + } + squashfs_finish_page(output); + } + + kfree(bh); + return length; + +block_release: + for (; k < b; k++) + put_bh(bh[k]); + +read_failure: + ERROR("squashfs_read_data failed to read block 0x%llx\n", + (unsigned long long) index); + kfree(bh); + return -EIO; +} |