1 files changed, 42 insertions, 1 deletions

diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index b5c68567077e..c99e9058c198 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -85,7 +85,7 @@
 #define OCFS2_CLEAR_INCOMPAT_FEATURE(sb,mask)                   \
         OCFS2_SB(sb)->s_feature_incompat &= ~(mask)
 
-#define OCFS2_FEATURE_COMPAT_SUPP       0
+#define OCFS2_FEATURE_COMPAT_SUPP       OCFS2_FEATURE_COMPAT_BACKUP_SB
 #define OCFS2_FEATURE_INCOMPAT_SUPP     OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT
 #define OCFS2_FEATURE_RO_COMPAT_SUPP    0
 
@@ -110,6 +110,20 @@
 #define OCFS2_FEATURE_INCOMPAT_SPARSE_ALLOC     0x0010
 
 /*
+ * backup superblock flag is used to indicate that this volume
+ * has backup superblocks.
+ */
+#define OCFS2_FEATURE_COMPAT_BACKUP_SB          0x0001
+
+/* The byte offset of the first backup block will be 1G.
+ * The following will be 4G, 16G, 64G, 256G and 1T.
+ */
+#define OCFS2_BACKUP_SB_START                   1 << 30
+
+/* the max backup superblock nums */
+#define OCFS2_MAX_BACKUP_SUPERBLOCKS    6
+
+/*
  * Flags on ocfs2_dinode.i_flags
  */
 #define OCFS2_VALID_FL          (0x00000001)    /* Inode is valid */
@@ -566,6 +580,20 @@ static inline int ocfs2_truncate_recs_per_inode(struct super_block *sb)
 
         return size / sizeof(struct ocfs2_truncate_rec);
 }
+
+static inline u64 ocfs2_backup_super_blkno(struct super_block *sb, int index)
+{
+        u64 offset = OCFS2_BACKUP_SB_START;
+
+        if (index >= 0 && index < OCFS2_MAX_BACKUP_SUPERBLOCKS) {
+                offset <<= (2 * index);
+                offset /= sb->s_blocksize;
+                return offset;
+        }
+
+        return 0;
+
+}
 #else
 static inline int ocfs2_fast_symlink_chars(int blocksize)
 {
@@ -631,6 +659,19 @@ static inline int ocfs2_truncate_recs_per_inode(int blocksize)
 
         return size / sizeof(struct ocfs2_truncate_rec);
 }
+
+static inline uint64_t ocfs2_backup_super_blkno(int blocksize, int index)
+{
+        uint64_t offset = OCFS2_BACKUP_SB_START;
+
+        if (index >= 0 && index < OCFS2_MAX_BACKUP_SUPERBLOCKS) {
+                offset <<= (2 * index);
+                offset /= blocksize;
+                return offset;
+        }
+
+        return 0;
+}
 #endif  /* __KERNEL__ */