xfs: rename xfs_buftarg structure members

In preparation for adding new members to the structure,
give these old ones more descriptive names:

	bt_ssize -> bt_meta_sectorsize
	bt_smask -> bt_meta_sectormask

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 584e092..3dc60ed 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1583,7 +1583,7 @@
 			XFS_IS_REALTIME_INODE(ip) ?
 			mp->m_rtdev_targp : mp->m_ddev_targp;
 
-		da.d_mem = da.d_miniosz = target->bt_ssize;
+		da.d_mem = da.d_miniosz = target->bt_meta_sectorsize;
 		da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);
 
 		if (copy_to_user(arg, &da, sizeof(da)))