Add XZ decompressor wrapper code.
Signed-off-by: Phillip Lougher <[email protected]>
---
fs/squashfs/squashfs_fs.h | 1 +
fs/squashfs/xz_wrapper.c | 153 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 154 insertions(+), 0 deletions(-)
create mode 100644 fs/squashfs/xz_wrapper.c
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index c5137fc..39533fe 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -238,6 +238,7 @@ struct meta_index {
#define ZLIB_COMPRESSION 1
#define LZMA_COMPRESSION 2
#define LZO_COMPRESSION 3
+#define XZ_COMPRESSION 4
struct squashfs_super_block {
__le32 s_magic;
diff --git a/fs/squashfs/xz_wrapper.c b/fs/squashfs/xz_wrapper.c
new file mode 100644
index 0000000..053fe35
--- /dev/null
+++ b/fs/squashfs/xz_wrapper.c
@@ -0,0 +1,153 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+ * Phillip Lougher <[email protected]>
+ *
+ * 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 "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs_fs_i.h"
+#include "squashfs.h"
+#include "decompressor.h"
+
+struct squashfs_xz {
+ struct xz_dec *state;
+ struct xz_buf buf;
+};
+
+static void *squashfs_xz_init(struct squashfs_sb_info *msblk)
+{
+ int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
+
+ struct squashfs_xz *stream = kmalloc(sizeof(*stream), GFP_KERNEL);
+ if (stream == NULL)
+ goto failed;
+ stream->state = xz_dec_init(XZ_PREALLOC, block_size);
+ if (stream->state == NULL)
+ goto failed;
+
+ return stream;
+
+failed:
+ ERROR("Failed to allocate xz workspace\n");
+ kfree(stream);
+ return NULL;
+}
+
+
+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 **buffer,
+ struct buffer_head **bh, int b, int offset, int length, int srclength,
+ int pages)
+{
+ enum xz_ret xz_err;
+ int avail, total = 0, k = 0, page = 0;
+ struct squashfs_xz *stream = msblk->stream;
+
+ mutex_lock(&msblk->read_data_mutex);
+
+ 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 = buffer[page++];
+
+ do {
+ if (stream->buf.in_pos == stream->buf.in_size && k < b) {
+ avail = min(length, msblk->devblksize - offset);
+ length -= avail;
+ wait_on_buffer(bh[k]);
+ if (!buffer_uptodate(bh[k]))
+ goto release_mutex;
+
+ if (avail == 0) {
+ offset = 0;
+ put_bh(bh[k++]);
+ continue;
+ }
+
+ 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
+ && page < pages) {
+ stream->buf.out = buffer[page++];
+ 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);
+
+ if (xz_err != XZ_STREAM_END) {
+ ERROR("xz_dec_run error, data probably corrupt\n");
+ goto release_mutex;
+ }
+
+ if (k < b) {
+ ERROR("xz_uncompress error, input remaining\n");
+ goto release_mutex;
+ }
+
+ total += stream->buf.out_pos;
+ mutex_unlock(&msblk->read_data_mutex);
+ return total;
+
+release_mutex:
+ mutex_unlock(&msblk->read_data_mutex);
+
+ for (; k < b; k++)
+ put_bh(bh[k]);
+
+ return -EIO;
+}
+
+const struct squashfs_decompressor squashfs_xz_comp_ops = {
+ .init = squashfs_xz_init,
+ .free = squashfs_xz_free,
+ .decompress = squashfs_xz_uncompress,
+ .id = XZ_COMPRESSION,
+ .name = "xz",
+ .supported = 1
+};
+
--
1.6.3.3
On 2010-12-09 Phillip Lougher wrote:
> + stream->state = xz_dec_init(XZ_PREALLOC, block_size);
This sets the preallocated LZMA2 dictionary size to Squashfs block size,
which allows the best compression ratio for the given block size (bigger
values would be waste of memory). XZ decompressor needs about 30 KiB of
memory plus the dictionary. So with 1 MiB Squashfs block size a little
over 1 MiB of memory is needed by the XZ decompressor.
Would it be useful to support smaller dictionaries without reducing the
Squashfs block size? It would save RAM while increasing the Squashfs
image size less than if also the block size was reduced. Reasonable
dictionary sizes could be e.g. 75 %, 50 %, or 25 % of the Squashfs block
size. The size increase of the Squashfs image will vary a lot depending
on the files in it, but e.g. dict_size = block_size / 2 won't
necessarily increase the image size more than 1 %.
I don't know if this kind of RAM savings matter on embedded systems. I
hope someone else can comment. My point in this email is only to let
others know that reducing the RAM usage is possible without reducing the
Squashfs block size.
--
Lasse Collin | IRC: Larhzu @ IRCnet & Freenode