[mirror_ubuntu-artful-kernel.git] / fs / squashfs / block.c

/*
 * 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 <linux/bio.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(REQ_OP_READ, 0, 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(REQ_OP_READ, 0, 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_SIZE) {
					data = squashfs_next_page(output);
					pg_offset = 0;
				}
				avail = min_t(int, in, PAGE_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;
}
Commit	Line	Data
e2780ab1 PL	1	/*
	2	* Squashfs - a compressed read only filesystem for Linux
	3	*
	4	* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
d7f2ff67	5	* Phillip Lougher <phillip@squashfs.org.uk>
e2780ab1 PL	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>
e2780ab1 PL	32	#include <linux/string.h>
e2780ab1 PL	33	#include <linux/buffer_head.h>
2f8b5444	34	#include <linux/bio.h>
e2780ab1 PL	35
	36	#include "squashfs_fs.h"
	37	#include "squashfs_fs_sb.h"
e2780ab1	38	#include "squashfs.h"
4c0f0bb2	39	#include "decompressor.h"
846b730e	40	#include "page_actor.h"
e2780ab1 PL	41
	42	/*
	43	* Read the metadata block length, this is stored in the first two
	44	* bytes of the metadata block.
	45	*/
	46	static 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;
3689456b PL	68
	69	if (*offset == msblk->devblksize) {
	70	put_bh(bh);
	71	bh = sb_bread(sb, ++(*cur_index));
	72	if (bh == NULL)
	73	return NULL;
	74	*offset = 0;
	75	}
e2780ab1 PL	76	}
	77
	78	return bh;
	79	}
	80
	81
	82	/*
	83	* Read and decompress a metadata block or datablock. Length is non-zero
	84	* if a datablock is being read (the size is stored elsewhere in the
	85	* filesystem), otherwise the length is obtained from the first two bytes of
	86	* the metadata block. A bit in the length field indicates if the block
	87	* is stored uncompressed in the filesystem (usually because compression
ec9267b6 PL	88	* generated a larger block - this does occasionally happen with compression
ec9267b6 PL	89	* algorithms).
e2780ab1	90	*/
846b730e PL	91	int squashfs_read_data(struct super_block *sb, u64 index, int length,
846b730e PL	92	u64 next_index, struct squashfs_page_actor output)
e2780ab1 PL	93	{
	94	struct squashfs_sb_info *msblk = sb->s_fs_info;
	95	struct buffer_head **bh;
	96	int offset = index & ((1 << msblk->devblksize_log2) - 1);
	97	u64 cur_index = index >> msblk->devblksize_log2;
846b730e	98	int bytes, compressed, b = 0, k = 0, avail, i;
e2780ab1	99
846b730e	100	bh = kcalloc(((output->length + msblk->devblksize - 1)
e0d1f700	101	>> msblk->devblksize_log2) + 1, sizeof(*bh), GFP_KERNEL);
e2780ab1 PL	102	if (bh == NULL)
	103	return -ENOMEM;
	104
	105	if (length) {
	106	/*
	107	* Datablock.
	108	*/
	109	bytes = -offset;
	110	compressed = SQUASHFS_COMPRESSED_BLOCK(length);
	111	length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
	112	if (next_index)
	113	*next_index = index + length;
	114
	115	TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
846b730e	116	index, compressed ? "" : "un", length, output->length);
e2780ab1	117
846b730e	118	if (length < 0 \|\| length > output->length \|\|
e2780ab1 PL	119	(index + length) > msblk->bytes_used)
	120	goto read_failure;
	121
	122	for (b = 0; bytes < length; b++, cur_index++) {
	123	bh[b] = sb_getblk(sb, cur_index);
	124	if (bh[b] == NULL)
	125	goto block_release;
	126	bytes += msblk->devblksize;
	127	}
dfec8a14	128	ll_rw_block(REQ_OP_READ, 0, b, bh);
e2780ab1 PL	129	} else {
	130	/*
	131	* Metadata block.
	132	*/
	133	if ((index + 2) > msblk->bytes_used)
	134	goto read_failure;
	135
	136	bh[0] = get_block_length(sb, &cur_index, &offset, &length);
	137	if (bh[0] == NULL)
	138	goto read_failure;
	139	b = 1;
	140
	141	bytes = msblk->devblksize - offset;
	142	compressed = SQUASHFS_COMPRESSED(length);
	143	length = SQUASHFS_COMPRESSED_SIZE(length);
	144	if (next_index)
	145	*next_index = index + length + 2;
	146
	147	TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
	148	compressed ? "" : "un", length);
	149
846b730e	150	if (length < 0 \|\| length > output->length \|\|
e2780ab1 PL	151	(index + length) > msblk->bytes_used)
	152	goto block_release;
	153
	154	for (; bytes < length; b++) {
	155	bh[b] = sb_getblk(sb, ++cur_index);
	156	if (bh[b] == NULL)
	157	goto block_release;
	158	bytes += msblk->devblksize;
	159	}
dfec8a14	160	ll_rw_block(REQ_OP_READ, 0, b - 1, bh + 1);
e2780ab1 PL	161	}
e2780ab1 PL	162
9508c6b9 PL	163	for (i = 0; i < b; i++) {
	164	wait_on_buffer(bh[i]);
	165	if (!buffer_uptodate(bh[i]))
	166	goto block_release;
	167	}
	168
e2780ab1	169	if (compressed) {
846b730e PL	170	length = squashfs_decompress(msblk, bh, b, offset, length,
846b730e PL	171	output);
e6a6d379 PL	172	if (length < 0)
e6a6d379 PL	173	goto read_failure;
e2780ab1 PL	174	} else {
	175	/*
	176	* Block is uncompressed.
	177	*/
e0125262	178	int in, pg_offset = 0;
846b730e	179	void *data = squashfs_first_page(output);
e2780ab1 PL	180
	181	for (bytes = length; k < b; k++) {
	182	in = min(bytes, msblk->devblksize - offset);
	183	bytes -= in;
	184	while (in) {
09cbfeaf	185	if (pg_offset == PAGE_SIZE) {
846b730e	186	data = squashfs_next_page(output);
e2780ab1 PL	187	pg_offset = 0;
e2780ab1 PL	188	}
09cbfeaf	189	avail = min_t(int, in, PAGE_SIZE -
e2780ab1	190	pg_offset);
846b730e PL	191	memcpy(data + pg_offset, bh[k]->b_data + offset,
846b730e PL	192	avail);
e2780ab1 PL	193	in -= avail;
	194	pg_offset += avail;
	195	offset += avail;
	196	}
	197	offset = 0;
	198	put_bh(bh[k]);
	199	}
846b730e	200	squashfs_finish_page(output);
e2780ab1 PL	201	}
	202
	203	kfree(bh);
	204	return length;
	205
e2780ab1 PL	206	block_release:
	207	for (; k < b; k++)
	208	put_bh(bh[k]);
	209
	210	read_failure:
118e1ef6 PL	211	ERROR("squashfs_read_data failed to read block 0x%llx\n",
118e1ef6 PL	212	(unsigned long long) index);
e2780ab1 PL	213	kfree(bh);
	214	return -EIO;
	215	}