linux/fs/squashfs/xz_wrapper.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

194 lines
4.3 KiB
C

/*
* Squashfs - a compressed read only filesystem for Linux
*
* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
* 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.
*
* xz_wrapper.c
*/
#include <linux/mutex.h>
#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/xz.h>
#include <linux/bitops.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
#include "decompressor.h"
#include "page_actor.h"
struct squashfs_xz {
struct xz_dec *state;
struct xz_buf buf;
};
struct disk_comp_opts {
__le32 dictionary_size;
__le32 flags;
};
struct comp_opts {
int dict_size;
};
static void *squashfs_xz_comp_opts(struct squashfs_sb_info *msblk,
void *buff, int len)
{
struct disk_comp_opts *comp_opts = buff;
struct comp_opts *opts;
int err = 0, n;
opts = kmalloc(sizeof(*opts), GFP_KERNEL);
if (opts == NULL) {
err = -ENOMEM;
goto out2;
}
if (comp_opts) {
/* check compressor options are the expected length */
if (len < sizeof(*comp_opts)) {
err = -EIO;
goto out;
}
opts->dict_size = le32_to_cpu(comp_opts->dictionary_size);
/* the dictionary size should be 2^n or 2^n+2^(n+1) */
n = ffs(opts->dict_size) - 1;
if (opts->dict_size != (1 << n) && opts->dict_size != (1 << n) +
(1 << (n + 1))) {
err = -EIO;
goto out;
}
} else
/* use defaults */
opts->dict_size = max_t(int, msblk->block_size,
SQUASHFS_METADATA_SIZE);
return opts;
out:
kfree(opts);
out2:
return ERR_PTR(err);
}
static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff)
{
struct comp_opts *comp_opts = buff;
struct squashfs_xz *stream;
int err;
stream = kmalloc(sizeof(*stream), GFP_KERNEL);
if (stream == NULL) {
err = -ENOMEM;
goto failed;
}
stream->state = xz_dec_init(XZ_PREALLOC, comp_opts->dict_size);
if (stream->state == NULL) {
kfree(stream);
err = -ENOMEM;
goto failed;
}
return stream;
failed:
ERROR("Failed to initialise xz decompressor\n");
return ERR_PTR(err);
}
static void squashfs_xz_free(void *strm)
{
struct squashfs_xz *stream = strm;
if (stream) {
xz_dec_end(stream->state);
kfree(stream);
}
}
static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
struct buffer_head **bh, int b, int offset, int length,
struct squashfs_page_actor *output)
{
enum xz_ret xz_err;
int avail, total = 0, k = 0;
struct squashfs_xz *stream = strm;
xz_dec_reset(stream->state);
stream->buf.in_pos = 0;
stream->buf.in_size = 0;
stream->buf.out_pos = 0;
stream->buf.out_size = PAGE_CACHE_SIZE;
stream->buf.out = squashfs_first_page(output);
do {
if (stream->buf.in_pos == stream->buf.in_size && k < b) {
avail = min(length, msblk->devblksize - offset);
length -= avail;
stream->buf.in = bh[k]->b_data + offset;
stream->buf.in_size = avail;
stream->buf.in_pos = 0;
offset = 0;
}
if (stream->buf.out_pos == stream->buf.out_size) {
stream->buf.out = squashfs_next_page(output);
if (stream->buf.out != NULL) {
stream->buf.out_pos = 0;
total += PAGE_CACHE_SIZE;
}
}
xz_err = xz_dec_run(stream->state, &stream->buf);
if (stream->buf.in_pos == stream->buf.in_size && k < b)
put_bh(bh[k++]);
} while (xz_err == XZ_OK);
squashfs_finish_page(output);
if (xz_err != XZ_STREAM_END || k < b)
goto out;
return total + stream->buf.out_pos;
out:
for (; k < b; k++)
put_bh(bh[k]);
return -EIO;
}
const struct squashfs_decompressor squashfs_xz_comp_ops = {
.init = squashfs_xz_init,
.comp_opts = squashfs_xz_comp_opts,
.free = squashfs_xz_free,
.decompress = squashfs_xz_uncompress,
.id = XZ_COMPRESSION,
.name = "xz",
.supported = 1
};