+/*
+ * Superblock - on disk version. Must match the in core version above.
+ * Must be padded to 64 bit alignment.
+ */
+typedef struct xfs_dsb {
+ __be32 sb_magicnum; /* magic number == XFS_SB_MAGIC */
+ __be32 sb_blocksize; /* logical block size, bytes */
+ __be64 sb_dblocks; /* number of data blocks */
+ __be64 sb_rblocks; /* number of realtime blocks */
+ __be64 sb_rextents; /* number of realtime extents */
+ uuid_t sb_uuid; /* file system unique id */
+ __be64 sb_logstart; /* starting block of log if internal */
+ __be64 sb_rootino; /* root inode number */
+ __be64 sb_rbmino; /* bitmap inode for realtime extents */
+ __be64 sb_rsumino; /* summary inode for rt bitmap */
+ __be32 sb_rextsize; /* realtime extent size, blocks */
+ __be32 sb_agblocks; /* size of an allocation group */
+ __be32 sb_agcount; /* number of allocation groups */
+ __be32 sb_rbmblocks; /* number of rt bitmap blocks */
+ __be32 sb_logblocks; /* number of log blocks */
+ __be16 sb_versionnum; /* header version == XFS_SB_VERSION */
+ __be16 sb_sectsize; /* volume sector size, bytes */
+ __be16 sb_inodesize; /* inode size, bytes */
+ __be16 sb_inopblock; /* inodes per block */
+ char sb_fname[12]; /* file system name */
+ __u8 sb_blocklog; /* log2 of sb_blocksize */
+ __u8 sb_sectlog; /* log2 of sb_sectsize */
+ __u8 sb_inodelog; /* log2 of sb_inodesize */
+ __u8 sb_inopblog; /* log2 of sb_inopblock */
+ __u8 sb_agblklog; /* log2 of sb_agblocks (rounded up) */
+ __u8 sb_rextslog; /* log2 of sb_rextents */
+ __u8 sb_inprogress; /* mkfs is in progress, don't mount */
+ __u8 sb_imax_pct; /* max % of fs for inode space */
+ /* statistics */
+ /*
+ * These fields must remain contiguous. If you really
+ * want to change their layout, make sure you fix the
+ * code in xfs_trans_apply_sb_deltas().
+ */
+ __be64 sb_icount; /* allocated inodes */
+ __be64 sb_ifree; /* free inodes */
+ __be64 sb_fdblocks; /* free data blocks */
+ __be64 sb_frextents; /* free realtime extents */
+ /*
+ * End contiguous fields.
+ */
+ __be64 sb_uquotino; /* user quota inode */
+ __be64 sb_gquotino; /* group quota inode */
+ __be16 sb_qflags; /* quota flags */
+ __u8 sb_flags; /* misc. flags */
+ __u8 sb_shared_vn; /* shared version number */
+ __be32 sb_inoalignmt; /* inode chunk alignment, fsblocks */
+ __be32 sb_unit; /* stripe or raid unit */
+ __be32 sb_width; /* stripe or raid width */
+ __u8 sb_dirblklog; /* log2 of dir block size (fsbs) */
+ __u8 sb_logsectlog; /* log2 of the log sector size */
+ __be16 sb_logsectsize; /* sector size for the log, bytes */
+ __be32 sb_logsunit; /* stripe unit size for the log */
+ __be32 sb_features2; /* additional feature bits */
+ /*
+ * bad features2 field as a result of failing to pad the sb
+ * structure to 64 bits. Some machines will be using this field
+ * for features2 bits. Easiest just to mark it bad and not use
+ * it for anything else.
+ */
+ __be32 sb_bad_features2;
+
+ /* must be padded to 64 bit alignment */
+} xfs_dsb_t;
+