zram: add lz4hc compression backend support

Add s/w lz4hc 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 LZ4_COMPRESS
 	select LZ4_DECOMPRESS
 
+config ZRAM_BACKEND_LZ4HC
+	bool "lz4hc compression support"
+	depends on ZRAM
+	select LZ4HC_COMPRESS
+	select LZ4_DECOMPRESS
+
 choice
 	prompt "Default zram compressor"
 	default ZRAM_DEF_COMP_LZORLE
···
 	bool "lz4"
 	depends on ZRAM_BACKEND_LZ4
 
+config ZRAM_DEF_COMP_LZ4HC
+	bool "lz4hc"
+	depends on ZRAM_BACKEND_LZ4HC
+
 endchoice
 
 config ZRAM_DEF_COMP
···
 	default "lzo-rle" if ZRAM_DEF_COMP_LZORLE
 	default "lzo" if ZRAM_DEF_COMP_LZO
 	default "lz4" if ZRAM_DEF_COMP_LZ4
+	default "lz4hc" if ZRAM_DEF_COMP_LZ4HC
 	default "unset-value"
 
 config ZRAM_WRITEBACK

drivers/block/zram/Makefile

···
 
 zram-y	:=	zcomp.o zram_drv.o
 
-zram-$(CONFIG_ZRAM_BACKEND_LZO)	+= backend_lzorle.o backend_lzo.o
-zram-$(CONFIG_ZRAM_BACKEND_LZ4)	+= backend_lz4.o
+zram-$(CONFIG_ZRAM_BACKEND_LZO)		+= backend_lzorle.o backend_lzo.o
+zram-$(CONFIG_ZRAM_BACKEND_LZ4)		+= backend_lz4.o
+zram-$(CONFIG_ZRAM_BACKEND_LZ4HC)	+= backend_lz4hc.o
 
 obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/backend_lz4hc.c

···
+#include <linux/kernel.h>
+#include <linux/lz4.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#include "backend_lz4hc.h"
+
+struct lz4hc_ctx {
+	void *mem;
+	s32 level;
+};
+
+static void lz4hc_destroy(void *ctx)
+{
+	struct lz4hc_ctx *zctx = ctx;
+
+	vfree(zctx->mem);
+	kfree(zctx);
+}
+
+static void *lz4hc_create(void)
+{
+	struct lz4hc_ctx *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	/* @FIXME: using a hardcoded LZ4HC_DEFAULT_CLEVEL for now */
+	ctx->level = LZ4HC_DEFAULT_CLEVEL;
+	ctx->mem = vmalloc(LZ4HC_MEM_COMPRESS);
+	if (!ctx->mem)
+		goto error;
+
+	return ctx;
+error:
+	lz4hc_destroy(ctx);
+	return NULL;
+}
+
+static int lz4hc_compress(void *ctx, const unsigned char *src, size_t src_len,
+			  unsigned char *dst, size_t *dst_len)
+{
+	struct lz4hc_ctx *zctx = ctx;
+	int ret;
+
+	ret = LZ4_compress_HC(src, dst, src_len, *dst_len,
+			      zctx->level, zctx->mem);
+	if (!ret)
+		return -EINVAL;
+	*dst_len = ret;
+	return 0;
+}
+
+static int lz4hc_decompress(void *ctx, const unsigned char *src,
+			    size_t src_len, unsigned char *dst, size_t dst_len)
+{
+	int ret;
+
+	ret = LZ4_decompress_safe(src, dst, src_len, dst_len);
+	if (ret < 0)
+		return -EINVAL;
+	return 0;
+}
+
+const struct zcomp_ops backend_lz4hc = {
+	.compress	= lz4hc_compress,
+	.decompress	= lz4hc_decompress,
+	.create_ctx	= lz4hc_create,
+	.destroy_ctx	= lz4hc_destroy,
+	.name		= "lz4hc",
+};

drivers/block/zram/backend_lz4hc.h

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#ifndef __BACKEND_LZ4HC_H__
+#define __BACKEND_LZ4HC_H__
+
+#include "zcomp.h"
+
+extern const struct zcomp_ops backend_lz4hc;
+
+#endif /* __BACKEND_LZ4HC_H__ */

drivers/block/zram/zcomp.c

···
 #include "backend_lzo.h"
 #include "backend_lzorle.h"
 #include "backend_lz4.h"
+#include "backend_lz4hc.h"
 
 static const struct zcomp_ops *backends[] = {
 #if IS_ENABLED(CONFIG_ZRAM_BACKEND_LZO)
···
 #endif
 #if IS_ENABLED(CONFIG_ZRAM_BACKEND_LZ4)
 	&backend_lz4,
+#endif
+#if IS_ENABLED(CONFIG_ZRAM_BACKEND_LZ4HC)
+	&backend_lz4hc,
 #endif
 	NULL
 };