xfs: introduce xfs_sb.c for sharing with libxfs

xfs_mount.c is shared with userspace, but the only functions that
are shared are to do with physical superblock manipulations. This
means that less than 25% of the xfs_mount.c code is actually shared
with userspace. Move all the superblock functions to xfs_sb.c and
share that instead with libxfs.

Note that this will leave all the in-core transaction related
superblock counter modifications in xfs_mount.c as none of that is
shared with userspace. With a few more small changes, xfs_mount.h
won't need to be shared with userspace anymore, either.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index 40b003e..91e163a 100644
--- a/fs/xfs/xfs_sb.h
+++ b/fs/xfs/xfs_sb.h
@@ -26,6 +26,7 @@
 
 struct xfs_buf;
 struct xfs_mount;
+struct xfs_trans;
 
 #define	XFS_SB_MAGIC		0x58465342	/* 'XFSB' */
 #define	XFS_SB_VERSION_1	1		/* 5.3, 6.0.1, 6.1 */
@@ -674,4 +675,23 @@
 #define XFS_B_TO_FSBT(mp,b)	(((__uint64_t)(b)) >> (mp)->m_sb.sb_blocklog)
 #define XFS_B_FSB_OFFSET(mp,b)	((b) & (mp)->m_blockmask)
 
+/*
+ * perag get/put wrappers for ref counting
+ */
+extern struct xfs_perag *xfs_perag_get(struct xfs_mount *, xfs_agnumber_t);
+extern struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *, xfs_agnumber_t,
+					   int tag);
+extern void	xfs_perag_put(struct xfs_perag *pag);
+extern int	xfs_initialize_perag_data(struct xfs_mount *, xfs_agnumber_t);
+
+extern void	xfs_sb_calc_crc(struct xfs_buf	*);
+extern void	xfs_mod_sb(struct xfs_trans *, __int64_t);
+extern void	xfs_sb_mount_common(struct xfs_mount *, struct xfs_sb *);
+extern void	xfs_sb_from_disk(struct xfs_sb *, struct xfs_dsb *);
+extern void	xfs_sb_to_disk(struct xfs_dsb *, struct xfs_sb *, __int64_t);
+extern void	xfs_sb_quota_from_disk(struct xfs_sb *sbp);
+
+extern const struct xfs_buf_ops xfs_sb_buf_ops;
+extern const struct xfs_buf_ops xfs_sb_quiet_buf_ops;
+
 #endif	/* __XFS_SB_H__ */