zram: add support for dict comp config

Handle dict=path algorithm param so that we can read a pre-trained
compression algorithm dictionary which we then pass to the backend
configuration.

Link: https://lkml.kernel.org/r/20240902105656.1383858-17-senozhatsky@chromium.orgSigned-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/zram_drv.c

@@ -33,6 +33,7 @@
 #include <linux/debugfs.h>
 #include <linux/cpuhotplug.h>
 #include <linux/part_stat.h>
+#include <linux/kernel_read_file.h>
 
 #include "zram_drv.h"
 
@@ -998,8 +999,34 @@ static int __comp_algorithm_store(struct zram *zram, u32 prio, const char *buf)
 	return 0;
 }
 
-static int comp_params_store(struct zram *zram, u32 prio, s32 level)
+static void comp_params_reset(struct zram *zram, u32 prio)
 {
+	struct zcomp_params *params = &zram->params[prio];
+
+	vfree(params->dict);
+	params->level = ZCOMP_PARAM_NO_LEVEL;
+	params->dict_sz = 0;
+	params->dict = NULL;
+}
+
+static int comp_params_store(struct zram *zram, u32 prio, s32 level,
+			     const char *dict_path)
+{
+	ssize_t sz = 0;
+
+	comp_params_reset(zram, prio);
+
+	if (dict_path) {
+		sz = kernel_read_file_from_path(dict_path, 0,
+						&zram->params[prio].dict,
+						INT_MAX,
+						NULL,
+						READING_POLICY);
+		if (sz < 0)
+			return -EINVAL;
+	}
+
+	zram->params[prio].dict_sz = sz;
 	zram->params[prio].level = level;
 	return 0;
 }
@@ -1010,7 +1037,7 @@ static ssize_t algorithm_params_store(struct device *dev,
 				      size_t len)
 {
 	s32 prio = ZRAM_PRIMARY_COMP, level = ZCOMP_PARAM_NO_LEVEL;
-	char *args, *param, *val, *algo = NULL;
+	char *args, *param, *val, *algo = NULL, *dict_path = NULL;
 	struct zram *zram = dev_to_zram(dev);
 	int ret;
 
@@ -1039,6 +1066,11 @@ static ssize_t algorithm_params_store(struct device *dev,
 			algo = val;
 			continue;
 		}
+
+		if (!strcmp(param, "dict")) {
+			dict_path = val;
+			continue;
+		}
 	}
 
 	/* Lookup priority by algorithm name */
@@ -1060,7 +1092,7 @@ static ssize_t algorithm_params_store(struct device *dev,
 	if (prio < ZRAM_PRIMARY_COMP || prio >= ZRAM_MAX_COMPS)
 		return -EINVAL;
 
-	ret = comp_params_store(zram, prio, level);
+	ret = comp_params_store(zram, prio, level, dict_path);
 	return ret ? ret : len;
 }
 
@@ -2050,12 +2082,7 @@ static void zram_comp_params_reset(struct zram *zram)
 	u32 prio;
 
 	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
-		struct zcomp_params *params = &zram->params[prio];
-
-		vfree(params->dict);
-		params->level = ZCOMP_PARAM_NO_LEVEL;
-		params->dict_sz = 0;
-		params->dict = NULL;
+		comp_params_reset(zram, prio);
 	}
 }