Add a command to display a bcache superblock.

1 files changed, 145 insertions, 0 deletions

diff --git a/bcache-super-show.c b/bcache-super-show.c
new file mode 100644
index 0000000..6f9f6a7
--- /dev/null
+++ b/bcache-super-show.c
@@ -0,0 +1,145 @@
+#define _FILE_OFFSET_BITS	64
+#define __USE_FILE_OFFSET64
+#define _XOPEN_SOURCE 500
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <linux/fs.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <uuid/uuid.h>
+
+#include "bcache.h"
+
+
+static void usage()
+{
+	fprintf(stderr, "Usage: bcache-super-show [-f] <device>\n");
+}
+
+
+int main(int argc, char **argv)
+{
+	bool force_csum = false;
+	int o;
+	extern char *optarg;
+	struct cache_sb sb;
+	char uuid[40];
+	uint64_t expected_csum;
+
+	while ((o = getopt(argc, argv, "f")) != EOF)
+		switch (o) {
+			case 'f':
+				force_csum = 1;
+				break;
+
+			default:
+				usage();
+				exit(1);
+		}
+
+	argv += optind;
+	argc -= optind;
+
+	if (argc != 1) {
+		usage();
+		exit(1);
+	}
+
+	int fd = open(argv[0], O_RDONLY);
+	if (fd < 0) {
+		printf("Can't open dev %s: %s\n", argv[0], strerror(errno));
+		exit(2);
+	}
+
+	if (pread(fd, &sb, sizeof(sb), 4096) != sizeof(sb)) {
+		fprintf(stderr, "Couldn't read\n");
+		exit(2);
+	}
+
+	printf("sb.magic\t\t");
+	if (! memcmp(sb.magic, bcache_magic, 16)) {
+		printf("ok\n");
+	} else {
+		printf("bad magic\n");
+		fprintf(stderr, "Invalid superblock (bad magic)\n");
+		exit(2);
+	}
+
+	printf("sb.first_sector\t\t%" PRIu64, sb.offset);
+	if (sb.offset == SB_SECTOR) {
+		printf(" [match]\n");
+	} else {
+		printf(" [expected %ds]\n", SB_SECTOR);
+		fprintf(stderr, "Invalid superblock (bad sector)\n");
+		exit(2);
+	}
+
+	printf("sb.csum\t\t\t0x%" PRIx64, sb.csum);
+	expected_csum = csum_set(&sb);
+	if (sb.csum == expected_csum) {
+		printf(" [match]\n");
+	} else {
+		printf(" [expected %" PRIX64 "]\n", expected_csum);
+		if (! force_csum) {
+			fprintf(stderr, "Corrupt superblock (bad csum)\n");
+			exit(2);
+		}
+	}
+
+	printf("sb.version\t\t%" PRIu64, sb.version);
+	switch (sb.version) {
+		case 1:
+			printf(" [backing device]\n");
+			break;
+
+		case 2:
+			printf(" [cache device]\n");
+			break;
+
+		case 3:
+			printf(" [backing device with offset]\n");
+			// XXX Kernel side bcache.h says different, and implements neither
+			return 0; //break;
+
+		default:
+			printf(" [unknown]\n");
+			// exit code?
+			return 0;
+	}
+
+	putchar('\n');
+
+	uuid_unparse(sb.uuid, uuid);
+	printf("dev.uuid\t\t%s\n", uuid);
+
+	printf(
+			"dev.sectors_per_block\t%u\n"
+			"dev.sectors_per_bucket\t%u\n"
+			"dev.bucket_count\t%ju\n"
+			"dev.cache_count\t\t%u\n" // expect version == 2 ? 1 : 0
+			"dev.data.first_bucket\t%u\n",
+			sb.block_size,
+			sb.bucket_size,
+			sb.nbuckets,
+			sb.nr_this_dev,
+			sb.first_bucket);
+
+	printf("dev.data.first_sector\t%u\n", sb.bucket_size * sb.first_bucket);
+	putchar('\n');
+
+	uuid_unparse(sb.set_uuid, uuid);
+	printf("cset.uuid\t\t%s\n", uuid);
+
+	printf("cset.cache_count\t%u\n\n", sb.nr_in_set);
+
+	return 0;
+}