zram: support deflate-specific params

Introduce support of algorithm specific parameters in algorithm_params
device attribute. The expected format is algorithm.param=value.

For starters, add support for deflate.winbits parameter.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sergey Senozhatsky <[e-mail]>
Reviewed-by: Mikhail Zaslonko <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

drivers/block/zram/backend_deflate.c

···
 #include "backend_deflate.h"
 
 /* Use the same value as crypto API */
-#define DEFLATE_DEF_WINBITS		11
+#define DEFLATE_DEF_WINBITS		(-11)
 #define DEFLATE_DEF_MEMLEVEL		MAX_MEM_LEVEL
 
 struct deflate_ctx {
···
 {
 	if (params->level == ZCOMP_PARAM_NOT_SET)
 		params->level = Z_DEFAULT_COMPRESSION;
+	if (params->deflate.winbits == ZCOMP_PARAM_NOT_SET)
+		params->deflate.winbits = DEFLATE_DEF_WINBITS;
 
 	return 0;
 }
···
 		return -ENOMEM;
 
 	ctx->context = zctx;
-	sz = zlib_deflate_workspacesize(-DEFLATE_DEF_WINBITS, MAX_MEM_LEVEL);
+	sz = zlib_deflate_workspacesize(params->deflate.winbits, MAX_MEM_LEVEL);
 	zctx->cctx.workspace = vzalloc(sz);
 	if (!zctx->cctx.workspace)
 		goto error;
 
 	ret = zlib_deflateInit2(&zctx->cctx, params->level, Z_DEFLATED,
-				-DEFLATE_DEF_WINBITS, DEFLATE_DEF_MEMLEVEL,
+				params->deflate.winbits, DEFLATE_DEF_MEMLEVEL,
 				Z_DEFAULT_STRATEGY);
 	if (ret != Z_OK)
 		goto error;
···
 	if (!zctx->dctx.workspace)
 		goto error;
 
-	ret = zlib_inflateInit2(&zctx->dctx, -DEFLATE_DEF_WINBITS);
+	ret = zlib_inflateInit2(&zctx->dctx, params->deflate.winbits);
 	if (ret != Z_OK)
 		goto error;
 

drivers/block/zram/zcomp.h

···
 
 #define ZCOMP_PARAM_NOT_SET	INT_MIN
 
+struct deflate_params {
+	s32 winbits;
+};
+
 /*
  * Immutable driver (backend) parameters. The driver may attach private
  * data to it (e.g. driver representation of the dictionary, etc.).
···
 	void *dict;
 	size_t dict_sz;
 	s32 level;
+	union {
+		struct deflate_params deflate;
+	};
 
 	void *drv_data;
 };

drivers/block/zram/zram_drv.c

···
 
 	vfree(params->dict);
 	params->level = ZCOMP_PARAM_NOT_SET;
+	params->deflate.winbits = ZCOMP_PARAM_NOT_SET;
 	params->dict_sz = 0;
 	params->dict = NULL;
 }
 
 static int comp_params_store(struct zram *zram, u32 prio, s32 level,
-			     const char *dict_path)
+			     const char *dict_path,
+			     struct deflate_params *deflate_params)
 {
 	ssize_t sz = 0;
 
···
 
 	zram->params[prio].dict_sz = sz;
 	zram->params[prio].level = level;
+	zram->params[prio].deflate.winbits = deflate_params->winbits;
 	return 0;
 }
 
···
 {
 	s32 prio = ZRAM_PRIMARY_COMP, level = ZCOMP_PARAM_NOT_SET;
 	char *args, *param, *val, *algo = NULL, *dict_path = NULL;
+	struct deflate_params deflate_params;
 	struct zram *zram = dev_to_zram(dev);
 	int ret;
+
+	deflate_params.winbits = ZCOMP_PARAM_NOT_SET;
 
 	args = skip_spaces(buf);
 	while (*args) {
···
 			dict_path = val;
 			continue;
 		}
+
+		if (!strcmp(param, "deflate.winbits")) {
+			ret = kstrtoint(val, 10, &deflate_params.winbits);
+			if (ret)
+				return ret;
+			continue;
+		}
 	}
 
 	/* Lookup priority by algorithm name */
···
 	if (prio < ZRAM_PRIMARY_COMP || prio >= ZRAM_MAX_COMPS)
 		return -EINVAL;
 
-	ret = comp_params_store(zram, prio, level, dict_path);
+	ret = comp_params_store(zram, prio, level, dict_path, &deflate_params);
 	return ret ? ret : len;
 }