linux/fs/squashfs/block.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
 * Phillip Lougher <[email protected]>
 *
 * block.c
 */

/*
 * This file implements the low-level routines to read and decompress
 * datablocks and metadata blocks.
 */

#include <linux/blkdev.h>
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/string.h>
#include <linux/bio.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
#include "decompressor.h"
#include "page_actor.h"

/*
 * Returns the amount of bytes copied to the page actor.
 */
static int copy_bio_to_actor(struct bio *bio,
			     struct squashfs_page_actor *actor,
			     int offset, int req_length)
{ … }

static int squashfs_bio_read_cached(struct bio *fullbio,
		struct address_space *cache_mapping, u64 index, int length,
		u64 read_start, u64 read_end, int page_count)
{ … }

static struct page *squashfs_get_cache_page(struct address_space *mapping,
					    pgoff_t index)
{ … }

static int squashfs_bio_read(struct super_block *sb, u64 index, int length,
			     struct bio **biop, int *block_offset)
{ … }

/*
 * 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)
{ … }