by Sergey Senozhatsky

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Subject: [PATCHv4 20/21] zram: add dictionary support to lz4hc

Support pre-trained dictionary param. Just like lz4,
lz4hc doesn't mandate specific format of the dictionary
and zstd --train can be used to train a dictionary for
lz4, according to [1].

TEST
====

- default lz4hc

/sys/block/zram0/mm_stat
1750315008 609010918 621006848 0 621006848 2 0 34288 34288

- lz4hc dict=/etc/dictionary

/sys/block/zram0/mm_stat
1750319104 499629401 509485056 0 509485056 1 0 34288 34288

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

Signed-off-by: Sergey Senozhatsky <[email protected]>
---
drivers/block/zram/backend_lz4hc.c | 54 ++++++++++++++++++++++++++----
1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/drivers/block/zram/backend_lz4hc.c b/drivers/block/zram/backend_lz4hc.c
index 428b393371d7..c928f94f30df 100644
--- a/drivers/block/zram/backend_lz4hc.c
+++ b/drivers/block/zram/backend_lz4hc.c
@@ -8,6 +8,12 @@
struct lz4hc_ctx {
void *mem;
s32 level;
+ LZ4_streamDecode_t *dstrm;
+ LZ4_streamHC_t *cstrm;
+
+ /* Shared between C/D streams */
+ void *dict;
+ size_t dict_sz;
};

static int lz4hc_init_config(struct zcomp_config *config)
@@ -26,6 +32,8 @@ static void lz4hc_destroy(void *ctx)
{
struct lz4hc_ctx *zctx = ctx;

+ kfree(zctx->dstrm);
+ kfree(zctx->cstrm);
vfree(zctx->mem);
kfree(zctx);
}
@@ -39,9 +47,22 @@ static void *lz4hc_create(struct zcomp_config *config)
return NULL;

ctx->level = config->level;
- ctx->mem = vmalloc(LZ4HC_MEM_COMPRESS);
- if (!ctx->mem)
- goto error;
+ if (!config->dict) {
+ ctx->mem = vmalloc(LZ4HC_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:
@@ -55,8 +76,18 @@ static int lz4hc_compress(void *ctx, const unsigned char *src,
struct lz4hc_ctx *zctx = ctx;
int ret;

- ret = LZ4_compress_HC(src, dst, PAGE_SIZE, *dst_len,
- zctx->level, zctx->mem);
+ if (!zctx->cstrm) {
+ ret = LZ4_compress_HC(src, dst, PAGE_SIZE, *dst_len,
+ zctx->level, zctx->mem);
+ } else {
+ /* Cstrm needs to be reset */
+ LZ4_resetStreamHC(zctx->cstrm, zctx->level);
+ ret = LZ4_loadDictHC(zctx->cstrm, zctx->dict, zctx->dict_sz);
+ if (ret != zctx->dict_sz)
+ return -EINVAL;
+ ret = LZ4_compress_HC_continue(zctx->cstrm, src, dst,
+ PAGE_SIZE, *dst_len);
+ }
if (!ret)
return -EINVAL;
*dst_len = ret;
@@ -66,10 +97,21 @@ static int lz4hc_compress(void *ctx, const unsigned char *src,
static int lz4hc_decompress(void *ctx, const unsigned char *src,
size_t src_len, unsigned char *dst)
{
+ struct lz4hc_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