bcache: Take data offset from the bdev superblock.

Add a new superblock version, and consolidate related defines.

Signed-off-by: Gabriel de Perthuis <g2p.code+bcache@gmail.com>
Signed-off-by: Kent Overstreet <koverstreet@google.com>

1 files changed, 37 insertions, 10 deletions

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index f05723565f17..340146d7c17f 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -223,11 +223,17 @@ struct bkey {
 #define BKEY_PADDED(key)                                        \
         union { struct bkey key; uint64_t key ## _pad[BKEY_PAD]; }
 
-/* Version 1: Backing device
+/* Version 0: Cache device
+ * Version 1: Backing device
  * Version 2: Seed pointer into btree node checksum
- * Version 3: New UUID format
+ * Version 3: Cache device with new UUID format
+ * Version 4: Backing device with data offset
  */
-#define BCACHE_SB_VERSION       3
+#define BCACHE_SB_VERSION_CDEV                  0
+#define BCACHE_SB_VERSION_BDEV                  1
+#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_SIZE                 4096
@@ -236,13 +242,12 @@ struct bkey {
 /* SB_JOURNAL_BUCKETS must be divisible by BITS_PER_LONG */
 #define MAX_CACHES_PER_SET      8
 
-#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];
 
@@ -257,12 +262,28 @@ struct cache_sb {
         uint64_t                seq;
         uint64_t                pad[8];
 
-        uint64_t                nbuckets;       /* device size */
-        uint16_t                block_size;     /* sectors */
-        uint16_t                bucket_size;    /* sectors */
+        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;
+                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 */
 
@@ -861,6 +882,12 @@ static inline bool key_merging_disabled(struct cache_set *c)
 #endif
 }
 
+static inline bool SB_IS_BDEV(const struct cache_sb *sb)
+{
+        return sb->version == BCACHE_SB_VERSION_BDEV
+                || sb->version == BCACHE_SB_VERSION_BDEV_WITH_OFFSET;
+}
+
 struct bbio {
         unsigned                submit_time_us;
         union {