[PATCH 04/10] zram: lz4hc: pre-initialize dictionary stream in setup_params

[Sergey Senozhatsky]

Pre-initialize the dictionary stream once in lz4hc_setup_params(), store
it in params->drv_data, and memcpy() it into the per-CPU stream before
LZ4_compress_HC_continue(), matching backend_lz4.  This avoids resetting
and hashing the dictionary on every page compression.

This also rejects dictionaries larger than 64 KB at device init time
(matching backend_lz4), instead of failing every page compression with
-EINVAL.

Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
 drivers/block/zram/backend_lz4hc.c | 31 +++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/drivers/block/zram/backend_lz4hc.c b/drivers/block/zram/backend_lz4hc.c
index 5c009835a684..f3656c27af21 100644
--- a/drivers/block/zram/backend_lz4hc.c
+++ b/drivers/block/zram/backend_lz4hc.c
@@ -18,10 +18,20 @@ struct lz4hc_ctx {
 
 static void lz4hc_release_params(struct zcomp_params *params)
 {
+	LZ4_streamHC_t *dict_stream = params->drv_data;
+
+	params->drv_data = NULL;
+	if (!dict_stream)
+		return;
+
+	vfree(dict_stream);
 }
 
 static int lz4hc_setup_params(struct zcomp_params *params)
 {
+	LZ4_streamHC_t *dict_stream;
+	int ret;
+
 	if (params->level == ZCOMP_PARAM_NOT_SET) {
 		params->level = LZ4HC_DEFAULT_CLEVEL;
 	} else if (params->level < 1 || params->level > LZ4HC_MAX_CLEVEL) {
@@ -35,6 +45,21 @@ static int lz4hc_setup_params(struct zcomp_params *params)
 		return -EINVAL;
 	}
 
+	if (!params->dict || !params->dict_sz)
+		return 0;
+
+	dict_stream = vzalloc(sizeof(*dict_stream));
+	if (!dict_stream)
+		return -ENOMEM;
+
+	LZ4_resetStreamHC(dict_stream, params->level);
+	ret = LZ4_loadDictHC(dict_stream, params->dict, params->dict_sz);
+	if (ret != params->dict_sz) {
+		vfree(dict_stream);
+		return -EINVAL;
+	}
+	params->drv_data = dict_stream;
+
 	return 0;
 }
 
@@ -93,11 +118,7 @@ static int lz4hc_compress(struct zcomp_params *params, struct zcomp_ctx *ctx,
 				      zctx->mem);
 	} else {
 		/* Cstrm needs to be reset */
-		LZ4_resetStreamHC(zctx->cstrm, params->level);
-		ret = LZ4_loadDictHC(zctx->cstrm, params->dict,
-				     params->dict_sz);
-		if (ret != params->dict_sz)
-			return -EINVAL;
+		memcpy(zctx->cstrm, params->drv_data, sizeof(*zctx->cstrm));
 		ret = LZ4_compress_HC_continue(zctx->cstrm, req->src, req->dst,
 					       req->src_len, req->dst_len);
 	}
-- 
2.56.0.rc1.315.gc6ed9934b7-goog