btrfs-progs: add support for generic global parameters

./btrfs --param key=value command ...
./btrfs --param key command ...

To pass various tuning data for testing and debugging, undocumented
for regular users.

To add support add reading of the parameter value after option parsing
bconf_param_value("key") and convert to what you need.

Signed-off-by: David Sterba <dsterba@suse.com>

btrfs.c

@@ -287,6 +287,7 @@ static int handle_global_options(int argc, char **argv)
 		{ "verbose", no_argument, NULL, 'v' },
 		{ "quiet", no_argument, NULL, 'q' },
 		{ "log", required_argument, NULL, OPT_LOG },
+		{ "param", required_argument, NULL, GETOPT_VAL_PARAM },
 		{ NULL, 0, NULL, 0}
 	};
 	int shift;
@@ -312,6 +313,9 @@ static int handle_global_options(int argc, char **argv)
 		case OPT_LOG:
 			handle_log_level(optarg);
 			break;
+		case GETOPT_VAL_PARAM:
+			bconf_save_param(optarg);
+			break;
 		case 'v':
 			bconf_be_verbose();
 			break;

common/help.h

@@ -36,6 +36,7 @@ struct cmd_group;
 #define GETOPT_VAL_TBYTES			519
 
 #define GETOPT_VAL_HELP				520
+#define GETOPT_VAL_PARAM			521
 
 #define ARGV0_BUF_SIZE	PATH_MAX
 

common/utils.c

@@ -944,6 +944,7 @@ void btrfs_config_init(void)
 {
 	bconf.output_format = CMD_FORMAT_TEXT;
 	bconf.verbose = BTRFS_BCONF_UNSET;
+	INIT_LIST_HEAD(&bconf.params);
 }
 
 void bconf_be_verbose(void)
@@ -959,6 +960,47 @@ void bconf_be_quiet(void)
 	bconf.verbose = BTRFS_BCONF_QUIET;
 }
 
+void bconf_add_param(const char *key, const char *value)
+{
+	struct config_param *param;
+
+	param = calloc(sizeof(*param), 1);
+	if (!param)
+		return;
+	param->key = strdup(key);
+	if (value)
+		param->value = strdup(value);
+	list_add(&param->list, &bconf.params);
+}
+
+const char *bconf_param_value(const char *key)
+{
+	struct config_param *param;
+
+	list_for_each_entry(param, &bconf.params, list) {
+		if (strcmp(key, param->key) == 0)
+			return param->value;
+	}
+	return NULL;
+}
+
+void bconf_save_param(const char *str)
+{
+	char *tmp;
+
+	tmp = strchr(str, '=');
+	if (!tmp) {
+		bconf_add_param(str, NULL);
+		printf("Global param: %s\n", str);
+	} else {
+		*tmp = 0;
+		bconf_add_param(str, tmp + 1);
+		printf("Global param: %s=%s\n", str, tmp + 1);
+		*tmp = '=';
+	}
+}
+
+
 /* Returns total size of main memory in bytes, -1UL if error. */
 unsigned long total_memory(void)
 {

common/utils.h

@@ -22,6 +22,7 @@
 #include "kerncompat.h"
 #include <stdbool.h>
 #include <stddef.h>
+#include "kernel-lib/list.h"
 #include "kernel-shared/volumes.h"
 #include "common/fsfeatures.h"
 
@@ -86,12 +87,22 @@ struct btrfs_config {
 	 *   > 0: verbose level
 	 */
 	int verbose;
+	struct list_head params;
 };
 extern struct btrfs_config bconf;
 
+struct config_param {
+	struct list_head list;
+	const char *key;
+	const char *value;
+};
+
 void btrfs_config_init(void);
 void bconf_be_verbose(void);
 void bconf_be_quiet(void);
+void bconf_add_param(const char *key, const char *value);
+void bconf_save_param(const char *str);
+const char *bconf_param_value(const char *key);
 
 /* Pseudo random number generator wrappers */
 int rand_int(void);