[PATCH 2/6] fs: squashfs: port lz4 compression support from kernel

[Sascha Hauer]

From: Enrico Jorns <ejo at pengutronix.de>

Signed-off-by: Enrico Jorns <ejo at pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 fs/squashfs/Kconfig       |  14 +++++
 fs/squashfs/Makefile      |   1 +
 fs/squashfs/lz4_wrapper.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 155 insertions(+)
 create mode 100644 fs/squashfs/lz4_wrapper.c

diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
index 7a6e5a2..9af34c0 100644
--- a/fs/squashfs/Kconfig
+++ b/fs/squashfs/Kconfig
@@ -17,6 +17,20 @@ menuconfig FS_SQUASHFS
 	  embedded systems where low overhead is needed.  Further information
 	  and tools are available from http://squashfs.sourceforge.net.
 
+config SQUASHFS_LZ4
+	bool "Include support for LZ4 compressed file systems"
+	default y if LZ4_DECOMPRESS
+	depends on FS_SQUASHFS
+	select LZ4_DECOMPRESS
+	help
+	  Saying Y here includes support for reading Squashfs file systems
+	  compressed with LZ4 compression.  LZ4 compression is mainly
+	  aimed at embedded systems with slower CPUs where the overheads
+	  of zlib are too high.
+
+	  LZ4 is not the standard compression used in Squashfs and so most
+	  file systems will be readable without selecting this option.
+
 config SQUASHFS_LZO
 	bool "Include support for LZO compressed file systems"
 	default y if LZO_DECOMPRESS
diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
index 447e15e..8590b09 100644
--- a/fs/squashfs/Makefile
+++ b/fs/squashfs/Makefile
@@ -12,3 +12,4 @@ obj-y	+= namei.o
 obj-y	+= super.o
 obj-$(CONFIG_SQUASHFS_XZ) += xz_wrapper.o
 obj-$(CONFIG_SQUASHFS_LZO) += lzo_wrapper.o
+obj-$(CONFIG_SQUASHFS_LZ4) += lz4_wrapper.o
diff --git a/fs/squashfs/lz4_wrapper.c b/fs/squashfs/lz4_wrapper.c
new file mode 100644
index 0000000..6ca6a32
--- /dev/null
+++ b/fs/squashfs/lz4_wrapper.c
@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2013, 2014
+ * Phillip Lougher <phillip at squashfs.org.uk>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+
+#include <types.h>
+#include <linux/mutex.h>
+#include <linux/lz4.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+#define LZ4_LEGACY	1
+
+struct lz4_comp_opts {
+	__le32 version;
+	__le32 flags;
+};
+
+struct squashfs_lz4 {
+	void *input;
+	void *output;
+};
+
+
+static void *lz4_comp_opts(struct squashfs_sb_info *msblk,
+	void *buff, int len)
+{
+	struct lz4_comp_opts *comp_opts = buff;
+
+	/* LZ4 compressed filesystems always have compression options */
+	if (comp_opts == NULL || len < sizeof(*comp_opts))
+		return ERR_PTR(-EIO);
+
+	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");
+		return ERR_PTR(-EINVAL);
+	}
+
+	return NULL;
+}
+
+
+static void *lz4_init(struct squashfs_sb_info *msblk, void *buff)
+{
+	int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
+	struct squashfs_lz4 *stream;
+
+	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(-ENOMEM);
+}
+
+
+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 *strm,
+	char **bh, int b, int offset, int length,
+	struct squashfs_page_actor *output)
+{
+	struct squashfs_lz4 *stream = strm;
+	void *buff = stream->input, *data;
+	int avail, i, bytes = length, res;
+	size_t dest_len = output->length;
+
+	for (i = 0; i < b; i++) {
+		avail = min(bytes, msblk->devblksize - offset);
+		memcpy(buff, bh[i] + offset, avail);
+		buff += avail;
+		bytes -= avail;
+		offset = 0;
+		kfree(bh[i]);
+	}
+
+	res = lz4_decompress_unknownoutputsize(stream->input, length,
+					stream->output, &dest_len);
+	if (res)
+		return -EIO;
+
+	bytes = dest_len;
+	data = squashfs_first_page(output);
+	buff = stream->output;
+	while (data) {
+		if (bytes <= PAGE_CACHE_SIZE) {
+			memcpy(data, buff, bytes);
+			break;
+		}
+		memcpy(data, buff, PAGE_CACHE_SIZE);
+		buff += PAGE_CACHE_SIZE;
+		bytes -= PAGE_CACHE_SIZE;
+		data = squashfs_next_page(output);
+	}
+	squashfs_finish_page(output);
+
+	return dest_len;
+}
+
+const struct squashfs_decompressor squashfs_lz4_comp_ops = {
+	.init = lz4_init,
+	.comp_opts = lz4_comp_opts,
+	.free = lz4_free,
+	.decompress = lz4_uncompress,
+	.id = LZ4_COMPRESSION,
+	.name = "lz4",
+	.supported = 1
+};
-- 
2.9.3