zram: add lz4 compression backend support

Add s/w lz4 compression support.

Link: https://lkml.kernel.org/r/20240902105656.1383858-7-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/zram/Kconfig

@@ -20,6 +20,12 @@ config ZRAM_BACKEND_LZO
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
 
+config ZRAM_BACKEND_LZ4
+	bool "lz4 compression support"
+	depends on ZRAM
+	select LZ4_COMPRESS
+	select LZ4_DECOMPRESS
+
 choice
 	prompt "Default zram compressor"
 	default ZRAM_DEF_COMP_LZORLE
@@ -33,12 +39,17 @@ config ZRAM_DEF_COMP_LZO
 	bool "lzo"
 	depends on ZRAM_BACKEND_LZO
 
+config ZRAM_DEF_COMP_LZ4
+	bool "lz4"
+	depends on ZRAM_BACKEND_LZ4
+
 endchoice
 
 config ZRAM_DEF_COMP
 	string
 	default "lzo-rle" if ZRAM_DEF_COMP_LZORLE
 	default "lzo" if ZRAM_DEF_COMP_LZO
+	default "lz4" if ZRAM_DEF_COMP_LZ4
 	default "unset-value"
 
 config ZRAM_WRITEBACK

drivers/block/zram/Makefile

@@ -3,5 +3,6 @@
 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
 
 obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/backend_lz4.c

@@ -0,0 +1,72 @@
+#include <linux/kernel.h>
+#include <linux/lz4.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#include "backend_lz4.h"
+
+struct lz4_ctx {
+	void *mem;
+	s32 level;
+};
+
+static void lz4_destroy(void *ctx)
+{
+	struct lz4_ctx *zctx = ctx;
+
+	vfree(zctx->mem);
+	kfree(zctx);
+}
+
+static void *lz4_create(void)
+{
+	struct lz4_ctx *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	/* @FIXME: using a hardcoded LZ4_ACCELERATION_DEFAULT for now */
+	ctx->level = LZ4_ACCELERATION_DEFAULT;
+	ctx->mem = vmalloc(LZ4_MEM_COMPRESS);
+	if (!ctx->mem)
+		goto error;
+
+	return ctx;
+error:
+	lz4_destroy(ctx);
+	return NULL;
+}
+
+static int lz4_compress(void *ctx, const unsigned char *src, size_t src_len,
+			unsigned char *dst, size_t *dst_len)
+{
+	struct lz4_ctx *zctx = ctx;
+	int ret;
+
+	ret = LZ4_compress_fast(src, dst, src_len, *dst_len,
+				zctx->level, zctx->mem);
+	if (!ret)
+		return -EINVAL;
+	*dst_len = ret;
+	return 0;
+}
+
+static int lz4_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_lz4 = {
+	.compress	= lz4_compress,
+	.decompress	= lz4_decompress,
+	.create_ctx	= lz4_create,
+	.destroy_ctx	= lz4_destroy,
+	.name		= "lz4",
+};

drivers/block/zram/backend_lz4.h

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#ifndef __BACKEND_LZ4_H__
+#define __BACKEND_LZ4_H__
+
+#include "zcomp.h"
+
+extern const struct zcomp_ops backend_lz4;
+
+#endif /* __BACKEND_LZ4_H__ */

drivers/block/zram/zcomp.c

@@ -14,11 +14,15 @@
 
 #include "backend_lzo.h"
 #include "backend_lzorle.h"
+#include "backend_lz4.h"
 
 static const struct zcomp_ops *backends[] = {
 #if IS_ENABLED(CONFIG_ZRAM_BACKEND_LZO)
 	&backend_lzorle,
 	&backend_lzo,
+#endif
+#if IS_ENABLED(CONFIG_ZRAM_BACKEND_LZ4)
+	&backend_lz4,
 #endif
 	NULL
 };