[PATCH 1/2] Squashfs: add LZ4 compression support

[Phillip Lougher <phillip@squashfs.org.uk>]

Add support for reading file systems compressed with the
LZ4 compression algorithm.

This patch adds the LZ4 decompressor wrapper code.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
---
 fs/squashfs/lz4_wrapper.c |  163 +++++++++++++++++++++++++++++++++++++++++++++
 fs/squashfs/squashfs_fs.h |    1 +
 2 files changed, 164 insertions(+)
 create mode 100644 fs/squashfs/lz4_wrapper.c

diff --git a/fs/squashfs/lz4_wrapper.c b/fs/squashfs/lz4_wrapper.c
new file mode 100644
index 0000000..681ed94
--- /dev/null
+++ b/fs/squashfs/lz4_wrapper.c
@@ -0,0 +1,163 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2013
+ * 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.
+ *
+ * lz4_wrapper.c
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/lz4.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+
+#define LZ4_LEGACY	1
+
+struct lz4_comp_opts {
+	__le32 version;
+	__le32 flags;
+};
+
+struct squashfs_lz4 {
+	void *input;
+	void *output;
+};
+
+
+
+static void *lz4_init(struct squashfs_sb_info *msblk, void *buff, int len)
+{
+	struct lz4_comp_opts *comp_opts = buff;
+	int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
+	struct squashfs_lz4 *stream;
+	int err = -ENOMEM;
+
+	/* LZ4 compressed filesystems always have compression options */
+	if(comp_opts == NULL || len < sizeof(*comp_opts)) {
+		err = -EIO;
+		goto failed;
+	}
+	if(le32_to_cpu(comp_opts->version) != LZ4_LEGACY) {
+		/* LZ4 format currently used by the kernel is the 'legacy'
+		 * format */
+		ERROR("Unknown LZ4 version\n");
+		err = -EINVAL;
+		goto failed;
+	}
+
+	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
+	if (stream == NULL)
+		goto failed;
+	stream->input = vmalloc(block_size);
+	if (stream->input == NULL)
+		goto failed2;
+	stream->output = vmalloc(block_size);
+	if (stream->output == NULL)
+		goto failed3;
+
+	return stream;
+
+failed3:
+	vfree(stream->input);
+failed2:
+	kfree(stream);
+failed:
+	ERROR("Failed to initialise LZ4 decompressor\n");
+	return ERR_PTR(err);
+}
+
+
+static void lz4_free(void *strm)
+{
+	struct squashfs_lz4 *stream = strm;
+
+	if (stream) {
+		vfree(stream->input);
+		vfree(stream->output);
+	}
+	kfree(stream);
+}
+
+
+static int lz4_uncompress(struct squashfs_sb_info *msblk, void **buffer,
+	struct buffer_head **bh, int b, int offset, int length, int srclength,
+	int pages)
+{
+	struct squashfs_lz4 *stream = msblk->stream;
+	void *buff = stream->input;
+	int avail, i, bytes = length, res;
+	size_t dest_len = srclength;
+
+	mutex_lock(&msblk->read_data_mutex);
+
+	for (i = 0; i < b; i++) {
+		wait_on_buffer(bh[i]);
+		if (!buffer_uptodate(bh[i]))
+			goto block_release;
+
+		avail = min(bytes, msblk->devblksize - offset);
+		memcpy(buff, bh[i]->b_data + offset, avail);
+		buff += avail;
+		bytes -= avail;
+		offset = 0;
+		put_bh(bh[i]);
+	}
+
+	res = lz4_decompress_unknownoutputsize(stream->input, length,
+					stream->output, &dest_len);
+	if (res)
+		goto failed;
+
+	bytes = dest_len;
+	for (i = 0, buff = stream->output; bytes && i < pages; i++) {
+		avail = min_t(int, bytes, PAGE_CACHE_SIZE);
+		memcpy(buffer[i], buff, avail);
+		buff += avail;
+		bytes -= avail;
+	}
+	if (bytes)
+		goto failed;
+
+	mutex_unlock(&msblk->read_data_mutex);
+	return dest_len;
+
+block_release:
+	for (; i < b; i++)
+		put_bh(bh[i]);
+
+failed:
+	mutex_unlock(&msblk->read_data_mutex);
+
+	ERROR("lz4 decompression failed, data probably corrupt\n");
+	return -EIO;
+}
+
+const struct squashfs_decompressor squashfs_lz4_comp_ops = {
+	.init = lz4_init,
+	.free = lz4_free,
+	.decompress = lz4_uncompress,
+	.id = LZ4_COMPRESSION,
+	.name = "lz4",
+	.supported = 1
+};
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index 9e2349d..ee0be5c 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -237,6 +237,7 @@ struct meta_index {
 #define LZMA_COMPRESSION	2
 #define LZO_COMPRESSION		3
 #define XZ_COMPRESSION		4
+#define LZ4_COMPRESSION		5
 
 struct squashfs_super_block {
 	__le32			s_magic;
-- 
1.7.10.4