New subcommand: set-option

This is for setting superblock options on existing filesystems, either
online or offline.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

bcachefs.c

@@ -33,6 +33,7 @@ static void usage(void)
 	     "Superblock commands:\n"
 	     "  format                   Format a new filesystem\n"
 	     "  show-super               Dump superblock information to stdout\n"
+	     "  set-option               Set a filesystem option\n"
 	     "\n"
 	     "Repair:\n"
 	     "  fsck                     Check an existing filesystem for errors\n"
@@ -199,6 +200,8 @@ int main(int argc, char *argv[])
 		return cmd_version(argc, argv);
 	if (!strcmp(cmd, "show-super"))
 		return cmd_show_super(argc, argv);
+	if (!strcmp(cmd, "set-option"))
+		return cmd_set_option(argc, argv);
 
 	if (argc < 2) {
 		printf("%s: missing command\n", argv[0]);

cmd_option.c

@@ -0,0 +1,104 @@
+/*
+ * Authors: Kent Overstreet <kent.overstreet@gmail.com>
+ *
+ * GPLv2
+ */
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <uuid/uuid.h>
+
+#include "cmds.h"
+#include "libbcachefs.h"
+#include "libbcachefs/opts.h"
+#include "libbcachefs/super-io.h"
+
+static void set_option_usage(void)
+{
+	puts("bcachefs set-option \n"
+	     "Usage: bcachefs set-option [OPTION].. device\n"
+	     "\n"
+	     "Options:\n");
+	bch2_opts_usage(OPT_MOUNT);
+	puts("  -h, --help                  display this help and exit\n"
+	     "Report bugs to <linux-bcachefs@vger.kernel.org>");
+	exit(EXIT_SUCCESS);
+}
+
+int cmd_set_option(int argc, char *argv[])
+{
+	struct bch_opt_strs new_opt_strs = bch2_cmdline_opts_get(&argc, argv, OPT_MOUNT);
+	struct bch_opts new_opts = bch2_parse_opts(new_opt_strs);
+	struct bch_opts open_opts = bch2_opts_empty();
+	unsigned i;
+	int opt, ret = 0;
+
+	opt_set(open_opts, nostart, true);
+
+	while ((opt = getopt(argc, argv, "h")) != -1)
+		switch (opt) {
+		case 'h':
+			set_option_usage();
+			break;
+		}
+	args_shift(optind);
+
+	if (!argc) {
+		fprintf(stderr, "Please supply device(s)\n");
+		exit(EXIT_FAILURE);
+	}
+
+	for (i = 0; i < argc; i++)
+		if (dev_mounted(argv[i]))
+			goto online;
+
+	struct bch_fs *c = bch2_fs_open(argv, argc, open_opts);
+	if (IS_ERR(c)) {
+		fprintf(stderr, "error opening %s: %s\n", argv[0], strerror(-PTR_ERR(c)));
+		exit(EXIT_FAILURE);
+	}
+
+	for (i = 0; i < bch2_opts_nr; i++) {
+		u64 v = bch2_opt_get_by_id(&new_opts, i);
+
+		if (!bch2_opt_defined_by_id(&new_opts, i))
+			continue;
+
+		ret = bch2_opt_check_may_set(c, i, v);
+		if (ret < 0) {
+			fprintf(stderr, "error setting %s: %i\n",
+				bch2_opt_table[i].attr.name, ret);
+			break;
+		}
+
+		bch2_opt_set_sb(c, bch2_opt_table + i, v);
+		bch2_opt_set_by_id(&c->opts, i, v);
+	}
+
+	bch2_fs_stop(c);
+	return ret;
+online:
+	unsigned dev_idx;
+	struct bchfs_handle fs = bchu_fs_open_by_dev(argv[i], &dev_idx);
+
+	for (i = 0; i < bch2_opts_nr; i++) {
+		if (!new_opt_strs.by_id[i])
+			continue;
+
+		char *path = mprintf("options/%s", bch2_opt_table[i].attr.name);
+
+		write_file_str(fs.sysfs_fd, path, new_opt_strs.by_id[i]);
+		free(path);
+	}
+	return 0;
+}

cmds.h

@@ -11,6 +11,7 @@
 
 int cmd_format(int argc, char *argv[]);
 int cmd_show_super(int argc, char *argv[]);
+int cmd_set_option(int argc, char *argv[]);
 
 #if 0
 int cmd_assemble(int argc, char *argv[]);

tools-util.c

@@ -128,6 +128,17 @@ struct stat xstat(const char *path)
 
 /* File parsing (i.e. sysfs) */
 
+void write_file_str(int dirfd, const char *path, const char *str)
+{
+	int fd = xopenat(dirfd, path, O_WRONLY);
+	ssize_t wrote, len = strlen(str);
+
+	wrote = write(fd, str, len);
+	if (wrote != len)
+		die("read error: %m");
+	close(fd);
+}
+
 char *read_file_str(int dirfd, const char *path)
 {
 	int fd = xopenat(dirfd, path, O_RDONLY);

tools-util.h

@@ -53,6 +53,7 @@ struct stat xstat(const char *);
 	_ret;								\
 })
 
+void write_file_str(int, const char *, const char *);
 char *read_file_str(int, const char *);
 u64 read_file_u64(int, const char *);