New superblock format

bcache.h

@@ -5,40 +5,52 @@ static const char bcache_magic[] = {
 	0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
 	0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81 };
 
+#define SB_LABEL_SIZE	32
+
+struct cache_sb {
+	uint64_t	csum;
+	uint64_t	offset_this_sb;
+	uint64_t	version;
+#define CACHE_BACKING_DEV	1
+
+	uint8_t		magic[16];
+
+	uint8_t		uuid[16];
+	uint8_t		set_uuid[16];
+	uint8_t		label[SB_LABEL_SIZE];
+
+#define CACHE_SYNC		(1U << 0)
+
+#define BDEV_WRITEBACK_BIT		0U
+
+#define BDEV_STATE_NONE		0U
+#define BDEV_STATE_CLEAN	1U
+#define BDEV_STATE_DIRTY	2U
+#define BDEV_STATE_STALE	3U
+	uint64_t	flags;
+	uint64_t	sequence;
+	uint64_t	pad[8];
+
+	uint64_t	nbuckets;	/* device size */
+	uint16_t	block_size;	/* sectors */
+	uint16_t	bucket_size;	/* sectors */
+
+	uint16_t	nr_in_set;
+	uint16_t	nr_this_dev;
+
+	uint32_t	last_mount;	/* time_t */
+
+	uint16_t	first_bucket;
+	uint16_t	njournal_buckets;
+	uint64_t	journal_buckets[];
+};
+
 struct bkey {
 	uint64_t	header;
 	uint64_t	key;
 	uint64_t	ptr[];
 };
 
-struct cache_sb {
-	uint8_t		magic[16];
-	uint8_t		uuid[16];
-	uint8_t		set_uuid[16];
-	uint64_t	sequence;
-
-#define CACHE_CLEAN		1
-#define CACHE_SYNC		2
-#define CACHE_BACKING_DEV	4
-	uint32_t	version;
-	uint16_t	block_size;	/* sectors */
-	uint16_t	bucket_size;	/* sectors */
-	uint32_t	journal_start;	/* buckets */
-	uint32_t	first_bucket;	/* start of data */
-	uint64_t	nbuckets;	/* device size */
-
-	union {
-		struct bkey	btree_root;
-		uint64_t	_pad[8];
-	};
-	uint16_t	btree_level;
-	uint16_t	nr_in_set;
-	uint16_t	nr_this_dev;
-	uint16_t	_pad[1];
-#define SB_LABEL_SIZE	32
-	uint8_t		label[SB_LABEL_SIZE];
-};
-
 struct bucket_disk {
 	uint16_t	priority;
 	uint8_t		generation;

make-bcache.c

@@ -2,6 +2,8 @@
 #define __USE_FILE_OFFSET64
 #define _XOPEN_SOURCE 600
 
+#include <ctype.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <stdbool.h>
@@ -64,7 +66,6 @@ void usage()
 	       "	-B Format a backing device\n"
 	       "	-b bucket size\n"
 	       "	-w block size (hard sector size of SSD, often 2k)\n"
-	       "	-j journal size, in buckets\n"
 	       "	-U UUID\n"
 	       "	-S Set UUID\n");
 	exit(EXIT_FAILURE);
@@ -73,9 +74,9 @@ void usage()
 int main(int argc, char **argv)
 {
 	bool cache = false, backingdev = false;
-	int64_t nblocks, journal = 0;
+	int fd, c;
-	int fd, i, c;
+	int64_t nblocks;
-	char uuid[40], set_uuid[40];
+	char uuid[40], set_uuid[40], *dev;
 	struct cache_sb sb;
 
 	memset(&sb, 0, sizeof(struct cache_sb));
@@ -97,9 +98,6 @@ int main(int argc, char **argv)
 		case 'w':
 			sb.block_size = hatoi(optarg) / 512;
 			break;
-		case 'j':
-			journal = atoi(optarg);
-			break;
 		case 'U':
 			if (uuid_parse(optarg, sb.uuid)) {
 				printf("Bad uuid\n");
@@ -130,51 +128,49 @@ int main(int argc, char **argv)
 		exit(EXIT_FAILURE);
 	}
 
-	fd = open(argv[optind], O_RDWR);
+	dev = argv[optind];
+	fd = open(dev, O_RDWR);
 	if (fd == -1) {
-		perror("Can't open dev\n");
+		printf("Can't open dev %s: %s\n", dev, strerror(errno));
 		exit(EXIT_FAILURE);
 	}
 	nblocks = getblocks(fd);
 	printf("device is %ju sectors\n", nblocks);
 
-	if (sb.bucket_size < sb.block_size ||
+	sb.offset_this_sb	= 8;
-	    sb.bucket_size > nblocks / 8) {
-		printf("Bad bucket size %i\n", sb.bucket_size);
-		exit(EXIT_FAILURE);
-	}
-
 	memcpy(sb.magic, bcache_magic, 16);
-	sb.version = backingdev ? CACHE_BACKING_DEV : 0;
+	sb.version		= backingdev ? CACHE_BACKING_DEV : 0;
-	sb.nbuckets = nblocks / sb.bucket_size;
+	sb.nbuckets		= nblocks / sb.bucket_size;
-	sb.nr_in_set = 1;
+	sb.nr_in_set		= 1;
 	uuid_unparse(sb.uuid, uuid);
 	uuid_unparse(sb.set_uuid, set_uuid);
 
-	sb.journal_start = ((sb.nbuckets * sizeof(struct bucket_disk)) + (24 << 9)) / (sb.bucket_size << 9) + 1;
+	sb.first_bucket = (23 / sb.bucket_size) + 1;
-	sb.first_bucket = sb.journal_start + journal;
 
-	printf("block_size:		%u\n"
+	if (cache)
-	       "bucket_size:		%u\n"
+		if (sb.bucket_size < sb.block_size ||
-	       "journal_start:		%u\n"
+		    sb.bucket_size > nblocks / 8) {
-	       "first_bucket:		%u\n"
+			printf("Bad bucket size %i\n", sb.bucket_size);
+			exit(EXIT_FAILURE);
+		}
+
+	printf("UUID:			%s\n"
+	       "Set UUID:		%s\n"
 	       "nbuckets:		%ju\n"
-	       "UUID:			%s\n"
+	       "block_size:		%u\n"
-	       "Set UUID:		%s\n",
+	       "bucket_size:		%u\n"
+	       "nr_in_set:		%u\n"
+	       "nr_this_dev:		%u\n"
+	       "first_bucket:		%u\n"
+	       "sizeof sb:		%lu\n",
+	       uuid, set_uuid,
+	       sb.nbuckets,
 	       sb.block_size,
 	       sb.bucket_size,
-	       sb.journal_start,
+	       sb.nr_in_set,
+	       sb.nr_this_dev,
 	       sb.first_bucket,
-	       sb.nbuckets,
+	       sizeof(sb));
-	       uuid, set_uuid);
-
-	if (!backingdev) {
-		/* Zero out priorities */
-		lseek(fd, 4096, SEEK_SET);
-		for (i = 8; i < sb.first_bucket * sb.bucket_size; i++)
-			if (write(fd, zero, 512) != 512)
-				goto err;
-	}
 
 	if (pwrite(fd, &sb, sizeof(sb), 4096) != sizeof(sb))
 		goto err;