zram: add 842 compression backend support

Add s/w 842 compression support.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sergey Senozhatsky <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Nick Terrell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

drivers/block/zram/Kconfig

···
 	select ZLIB_DEFLATE
 	select ZLIB_INFLATE
 
+config ZRAM_BACKEND_842
+	bool "842 compression support"
+	depends on ZRAM
+	select 842_COMPRESS
+	select 842_DECOMPRESS
+
 choice
 	prompt "Default zram compressor"
 	default ZRAM_DEF_COMP_LZORLE
···
 	bool "deflate"
 	depends on ZRAM_BACKEND_DEFLATE
 
+config ZRAM_DEF_COMP_842
+	bool "842"
+	depends on ZRAM_BACKEND_842
+
 endchoice
 
 config ZRAM_DEF_COMP
···
 	default "lz4hc" if ZRAM_DEF_COMP_LZ4HC
 	default "zstd" if ZRAM_DEF_COMP_ZSTD
 	default "deflate" if ZRAM_DEF_COMP_DEFLATE
+	default "842" if ZRAM_DEF_COMP_842
 	default "unset-value"
 
 config ZRAM_WRITEBACK

drivers/block/zram/Makefile

···
 zram-$(CONFIG_ZRAM_BACKEND_LZ4HC)	+= backend_lz4hc.o
 zram-$(CONFIG_ZRAM_BACKEND_ZSTD)	+= backend_zstd.o
 zram-$(CONFIG_ZRAM_BACKEND_DEFLATE)	+= backend_deflate.o
+zram-$(CONFIG_ZRAM_BACKEND_842)		+= backend_842.o
 
 obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/backend_842.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sw842.h>
+#include <linux/vmalloc.h>
+
+#include "backend_842.h"
+
+struct sw842_ctx {
+	void *mem;
+};
+
+static void destroy_842(void *ctx)
+{
+	struct sw842_ctx *zctx = ctx;
+
+	kfree(zctx->mem);
+	kfree(zctx);
+}
+
+static void *create_842(void)
+{
+	struct sw842_ctx *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	ctx->mem = kmalloc(SW842_MEM_COMPRESS, GFP_KERNEL);
+	if (!ctx->mem)
+		goto error;
+
+	return ctx;
+
+error:
+	destroy_842(ctx);
+	return NULL;
+}
+
+static int compress_842(void *ctx, const unsigned char *src, size_t src_len,
+			unsigned char *dst, size_t *dst_len)
+{
+	struct sw842_ctx *zctx = ctx;
+	unsigned int dlen = *dst_len;
+	int ret;
+
+	ret = sw842_compress(src, src_len, dst, &dlen, zctx->mem);
+	if (ret == 0)
+		*dst_len = dlen;
+	return ret;
+}
+
+static int decompress_842(void *ctx, const unsigned char *src, size_t src_len,
+			  unsigned char *dst, size_t dst_len)
+{
+	unsigned int dlen = dst_len;
+
+	return sw842_decompress(src, src_len, dst, &dlen);
+}
+
+const struct zcomp_ops backend_842 = {
+	.compress	= compress_842,
+	.decompress	= decompress_842,
+	.create_ctx	= create_842,
+	.destroy_ctx	= destroy_842,
+	.name		= "842",
+};

drivers/block/zram/backend_842.h

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#ifndef __BACKEND_842_H__
+#define __BACKEND_842_H__
+
+#include "zcomp.h"
+
+extern const struct zcomp_ops backend_842;
+
+#endif /* __BACKEND_842_H__ */

drivers/block/zram/zcomp.c

···
 #include "backend_lz4hc.h"
 #include "backend_zstd.h"
 #include "backend_deflate.h"
+#include "backend_842.h"
 
 static const struct zcomp_ops *backends[] = {
 #if IS_ENABLED(CONFIG_ZRAM_BACKEND_LZO)
···
 #endif
 #if IS_ENABLED(CONFIG_ZRAM_BACKEND_DEFLATE)
 	&backend_deflate,
+#endif
+#if IS_ENABLED(CONFIG_ZRAM_BACKEND_842)
+	&backend_842,
 #endif
 	NULL
 };