Update for new superblock version for data_offset

bcache.h

@@ -15,24 +15,27 @@ static const char bcache_magic[] = {
 	0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
 	0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81 };
 
-/* Version 1: Backing dev
+/*
+ * Version 0: Cache device
+ * Version 1: Backing device
  * Version 2: Seed pointer into btree node checksum
- * Version 3: Backing dev superblock has offset of start of data
+ * Version 3: Cache device with new UUID format
+ * Version 4: Backing device with data offset
  */
-
+#define BCACHE_SB_VERSION_CDEV			0
-#define BCACHE_SB_BDEV_VERSION	3
+#define BCACHE_SB_VERSION_BDEV			1
-#define BCACHE_SB_MAX_VERSION	3
+#define BCACHE_SB_VERSION_CDEV_WITH_UUID	3
+#define BCACHE_SB_VERSION_BDEV_WITH_OFFSET	4
+#define BCACHE_SB_MAX_VERSION			4
 
 #define SB_SECTOR		8
 #define SB_LABEL_SIZE		32
-#define BDEV_DATA_START		16	/* sectors */
+#define BDEV_DATA_START_DEFAULT	16	/* sectors */
-
 
 struct cache_sb {
 	uint64_t		csum;
 	uint64_t		offset;	/* sector where this sb was written */
 	uint64_t		version;
-#define CACHE_BACKING_DEV	1
 
 	uint8_t			magic[16];
 
@@ -47,17 +50,36 @@ struct cache_sb {
 	uint64_t		seq;
 	uint64_t		pad[8];
 
+	union {
+	struct {
+		/* Cache devices */
 		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;
+	};
+	struct {
+		/* Backing devices */
+		uint64_t	data_offset;
+
+		/*
+		 * block_size from the cache device section is still used by
+		 * backing devices, so don't add anything here until we fix
+		 * things to not need it for backing devices anymore
+		 */
+	};
+	};
 
 	uint32_t		last_mount;	/* time_t */
 
 	uint16_t		first_bucket;
-	uint16_t		keys;		/* number of journal buckets */
+	union {
+		uint16_t	njournal_buckets;
+		uint16_t	keys;
+	};
 	uint64_t		d[];	/* journal buckets */
 };
 

make-bcache.c

@@ -161,39 +161,49 @@ static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
 	char uuid_str[40], set_uuid_str[40];
 	struct cache_sb sb;
 
-	memset(&sb, 0, sizeof(struct cache_sb));
-
-	sb.version	= bdev ? CACHE_BACKING_DEV : 0;
-	sb.bucket_size	= bucket_size;
-	sb.block_size	= block_size;
-
-	uuid_generate(sb.uuid);
-	memcpy(sb.set_uuid, set_uuid, sizeof(sb.set_uuid));
-
-	if (SB_BDEV(&sb)) {
-		SET_BDEV_WRITEBACK(&sb, writeback);
-
-		if (data_offset != BDEV_DATA_START) {
-			sb.version = BCACHE_SB_BDEV_VERSION;
-			sb.keys = 1;
-			sb.d[0] = data_offset;
-		}
-	} else {
-		SET_CACHE_DISCARD(&sb, discard);
-		SET_CACHE_REPLACEMENT(&sb, cache_replacement_policy);
-	}
-
 	if ((fd = open(dev, O_RDWR|O_EXCL)) == -1) {
 		printf("Can't open dev %s: %s\n", dev, strerror(errno));
 		exit(EXIT_FAILURE);
 	}
 
+	memset(&sb, 0, sizeof(struct cache_sb));
+
 	sb.offset	= SB_SECTOR;
+	sb.version	= bdev
+		? BCACHE_SB_VERSION_BDEV
+		: BCACHE_SB_VERSION_CDEV;
+
 	memcpy(sb.magic, bcache_magic, 16);
+	uuid_generate(sb.uuid);
+	memcpy(sb.set_uuid, set_uuid, sizeof(sb.set_uuid));
+
+	sb.bucket_size	= bucket_size;
+	sb.block_size	= block_size;
+
+	uuid_unparse(sb.uuid, uuid_str);
+	uuid_unparse(sb.set_uuid, set_uuid_str);
+
+	if (SB_BDEV(&sb)) {
+		SET_BDEV_WRITEBACK(&sb, writeback);
+
+		if (data_offset != BDEV_DATA_START_DEFAULT) {
+			sb.version = BCACHE_SB_VERSION_BDEV_WITH_OFFSET;
+			sb.data_offset = data_offset;
+		}
+
+		printf("UUID:			%s\n"
+		       "Set UUID:		%s\n"
+		       "version:		%u\n"
+		       "block_size:		%u\n"
+		       "data_offset:		%ju\n",
+		       uuid_str, set_uuid_str,
+		       (unsigned) sb.version,
+		       sb.block_size,
+		       sb.data_offset);
+	} else {
 		sb.nbuckets		= getblocks(fd) / sb.bucket_size;
 		sb.nr_in_set		= 1;
 		sb.first_bucket		= (23 / sb.bucket_size) + 1;
-	sb.csum = csum_set(&sb);
 
 		if (sb.nbuckets < 1 << 7) {
 			printf("Not enough buckets: %ju, need %u\n",
@@ -201,8 +211,8 @@ static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
 			exit(EXIT_FAILURE);
 		}
 
-	uuid_unparse(sb.uuid, uuid_str);
+		SET_CACHE_DISCARD(&sb, discard);
-	uuid_unparse(sb.set_uuid, set_uuid_str);
+		SET_CACHE_REPLACEMENT(&sb, cache_replacement_policy);
 
 		printf("UUID:			%s\n"
 		       "Set UUID:		%s\n"
@@ -221,6 +231,9 @@ static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
 		       sb.nr_in_set,
 		       sb.nr_this_dev,
 		       sb.first_bucket);
+	}
+
+	sb.csum = csum_set(&sb);
 
 	if (pwrite(fd, &sb, sizeof(sb), SB_SECTOR << 9) != sizeof(sb)) {
 		perror("write error\n");
@@ -241,7 +254,7 @@ int main(int argc, char **argv)
 	unsigned block_size = 1, bucket_size = 1024;
 	int writeback = 0, discard = 0;
 	unsigned cache_replacement_policy = 0;
-	uint64_t data_offset = BDEV_DATA_START;
+	uint64_t data_offset = BDEV_DATA_START_DEFAULT;
 	uuid_t set_uuid;
 
 	uuid_generate(set_uuid);
@@ -289,8 +302,9 @@ int main(int argc, char **argv)
 			break;
 		case 'o':
 			data_offset = atoll(optarg);
-			if (data_offset < BDEV_DATA_START) {
+			if (data_offset < BDEV_DATA_START_DEFAULT) {
-				printf("Bad data offset; minimum %d sectors\n", BDEV_DATA_START);
+				printf("Bad data offset; minimum %d sectors\n",
+				       BDEV_DATA_START_DEFAULT);
 				exit(EXIT_FAILURE);
 			}
 			break;