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Subject[PATCHv3 17/19] zram: add dictionary support to lz4
Date
Support pre-trained dictionary param. lz4 doesn't
mandate specific format of the dictionary and even
zstd --train can be used to train a dictionary for
lz4, according to [1].

TEST
====

- default lz4

/sys/block/zram0/mm_stat
1750323200 664258735 676990976 0 676990976 2 0 34288 34288

- lz4 dict=/etc/dictionary

/sys/block/zram0/mm_stat
1750310912 620608254 632852480 0 632852480 1 0 34288 34288

[1] https://github.com/lz4/lz4/issues/557

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
drivers/block/zram/backend_lz4.c | 77 +++++++++++++++++++++++++++++---
1 file changed, 71 insertions(+), 6 deletions(-)

diff --git a/drivers/block/zram/backend_lz4.c b/drivers/block/zram/backend_lz4.c
index 560fcf139301..2c3b64058adf 100644
--- a/drivers/block/zram/backend_lz4.c
+++ b/drivers/block/zram/backend_lz4.c
@@ -1,9 +1,20 @@
#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;
+ LZ4_streamDecode_t *dstrm;
+ LZ4_stream_t *cstrm;
+
+ /* Shared between C/D streams */
+ void *dict;
+ size_t dict_sz;
+};
+
static int lz4_init_config(struct zcomp_config *config)
{
return 0;
@@ -13,22 +24,65 @@ static void lz4_release_config(struct zcomp_config *config)
{
}

-static void *lz4_create(struct zcomp_config *config)
+static void lz4_destroy(void *ctx)
{
- return vmalloc(LZ4_MEM_COMPRESS);
+ struct lz4_ctx *zctx = ctx;
+
+ kfree(zctx->dstrm);
+ kfree(zctx->cstrm);
+ vfree(zctx->mem);
+ kfree(zctx);
}

-static void lz4_destroy(void *ctx)
+static void *lz4_create(struct zcomp_config *config)
{
- vfree(ctx);
+ struct lz4_ctx *ctx;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return NULL;
+
+ if (!config->dict) {
+ ctx->mem = vmalloc(LZ4_MEM_COMPRESS);
+ if (!ctx->mem)
+ goto error;
+ } else {
+ ctx->dstrm = kzalloc(sizeof(*ctx->dstrm), GFP_KERNEL);
+ if (!ctx->dstrm)
+ goto error;
+
+ ctx->cstrm = kzalloc(sizeof(*ctx->cstrm), GFP_KERNEL);
+ if (!ctx->cstrm)
+ goto error;
+
+ ctx->dict = config->dict;
+ ctx->dict_sz = config->dict_sz;
+ }
+
+ return ctx;
+error:
+ lz4_destroy(ctx);
+ return NULL;
}

static int lz4_compress(void *ctx, const unsigned char *src,
unsigned char *dst, size_t *dst_len)
{
+ struct lz4_ctx *zctx = ctx;
int ret;

- ret = LZ4_compress_default(src, dst, PAGE_SIZE, *dst_len, ctx);
+ if (!zctx->cstrm) {
+ ret = LZ4_compress_default(src, dst, PAGE_SIZE, *dst_len,
+ zctx->mem);
+ } else {
+ /* Cstrm needs to be reset */
+ ret = LZ4_loadDict(zctx->cstrm, zctx->dict, zctx->dict_sz);
+ if (ret != zctx->dict_sz)
+ return -EINVAL;
+ ret = LZ4_compress_fast_continue(zctx->cstrm, src, dst,
+ PAGE_SIZE, *dst_len,
+ LZ4_ACCELERATION_DEFAULT);
+ }
if (!ret)
return -EINVAL;
*dst_len = ret;
@@ -38,10 +92,21 @@ static int lz4_compress(void *ctx, const unsigned char *src,
static int lz4_decompress(void *ctx, const unsigned char *src,
size_t src_len, unsigned char *dst)
{
+ struct lz4_ctx *zctx = ctx;
int dst_len = PAGE_SIZE;
int ret;

- ret = LZ4_decompress_safe(src, dst, src_len, dst_len);
+ if (!zctx->dstrm) {
+ ret = LZ4_decompress_safe(src, dst, src_len, dst_len);
+ } else {
+ /* Dstrm needs to be reset */
+ ret = LZ4_setStreamDecode(zctx->dstrm, zctx->dict,
+ zctx->dict_sz);
+ if (!ret)
+ return -EINVAL;
+ ret = LZ4_decompress_safe_continue(zctx->dstrm, src, dst,
+ src_len, dst_len);
+ }
if (ret < 0)
return -EINVAL;
return 0;
--
2.45.0.rc1.225.g2a3ae87e7f-goog

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