linux/fs/squashfs/decompressor.c
Phillip Lougher 846b730e99 Squashfs: Generalise paging handling in the decompressors
Further generalise the decompressors by adding a page handler
abstraction.  This adds helpers to allow the decompressors
to access and process the output buffers in an implementation
independant manner.

This allows different types of output buffer to be passed
to the decompressors, with the implementation specific
aspects handled at decompression time, but without the
knowledge being held in the decompressor wrapper code.

This will allow the decompressors to handle Squashfs
cache buffers, and page cache pages.

This patch adds the abstraction and an implementation for
the caches.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>
2013-11-20 03:59:01 +00:00

142 lines
3.5 KiB
C

/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
* 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.
*
* decompressor.c
*/
#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "decompressor.h"
#include "squashfs.h"
#include "page_actor.h"
/*
* This file (and decompressor.h) implements a decompressor framework for
* Squashfs, allowing multiple decompressors to be easily supported
*/
static const struct squashfs_decompressor squashfs_lzma_unsupported_comp_ops = {
NULL, NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0
};
#ifndef CONFIG_SQUASHFS_LZO
static const struct squashfs_decompressor squashfs_lzo_comp_ops = {
NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0
};
#endif
#ifndef CONFIG_SQUASHFS_XZ
static const struct squashfs_decompressor squashfs_xz_comp_ops = {
NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0
};
#endif
#ifndef CONFIG_SQUASHFS_ZLIB
static const struct squashfs_decompressor squashfs_zlib_comp_ops = {
NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0
};
#endif
static const struct squashfs_decompressor squashfs_unknown_comp_ops = {
NULL, NULL, NULL, NULL, 0, "unknown", 0
};
static const struct squashfs_decompressor *decompressor[] = {
&squashfs_zlib_comp_ops,
&squashfs_lzo_comp_ops,
&squashfs_xz_comp_ops,
&squashfs_lzma_unsupported_comp_ops,
&squashfs_unknown_comp_ops
};
const struct squashfs_decompressor *squashfs_lookup_decompressor(int id)
{
int i;
for (i = 0; decompressor[i]->id; i++)
if (id == decompressor[i]->id)
break;
return decompressor[i];
}
static void *get_comp_opts(struct super_block *sb, unsigned short flags)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
void *buffer = NULL, *comp_opts;
struct squashfs_page_actor *actor = NULL;
int length = 0;
/*
* Read decompressor specific options from file system if present
*/
if (SQUASHFS_COMP_OPTS(flags)) {
buffer = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
if (buffer == NULL) {
comp_opts = ERR_PTR(-ENOMEM);
goto out;
}
actor = squashfs_page_actor_init(&buffer, 1, 0);
if (actor == NULL) {
comp_opts = ERR_PTR(-ENOMEM);
goto out;
}
length = squashfs_read_data(sb,
sizeof(struct squashfs_super_block), 0, NULL, actor);
if (length < 0) {
comp_opts = ERR_PTR(length);
goto out;
}
}
comp_opts = squashfs_comp_opts(msblk, buffer, length);
out:
kfree(actor);
kfree(buffer);
return comp_opts;
}
void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
void *stream, *comp_opts = get_comp_opts(sb, flags);
if (IS_ERR(comp_opts))
return comp_opts;
stream = squashfs_decompressor_create(msblk, comp_opts);
if (IS_ERR(stream))
kfree(comp_opts);
return stream;
}