diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 5861b49..a62e897 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -103,6 +103,16 @@
 	xfs_mod_incore_sb(mp, field, delta, rsvd)
 #endif
 
+/* dynamic preallocation free space thresholds, 5% down to 1% */
+enum {
+	XFS_LOWSP_1_PCNT = 0,
+	XFS_LOWSP_2_PCNT,
+	XFS_LOWSP_3_PCNT,
+	XFS_LOWSP_4_PCNT,
+	XFS_LOWSP_5_PCNT,
+	XFS_LOWSP_MAX,
+};
+
 typedef struct xfs_mount {
 	struct super_block	*m_super;
 	xfs_tid_t		m_tid;		/* next unused tid for fs */
@@ -202,6 +212,8 @@
 	__int64_t		m_update_flags;	/* sb flags we need to update
 						   on the next remount,rw */
 	struct shrinker		m_inode_shrink;	/* inode reclaim shrinker */
+	int64_t			m_low_space[XFS_LOWSP_MAX];
+						/* low free space thresholds */
 } xfs_mount_t;
 
 /*
@@ -379,6 +391,8 @@
 
 extern int	xfs_dev_is_read_only(struct xfs_mount *, char *);
 
+extern void	xfs_set_low_space_thresholds(struct xfs_mount *);
+
 #endif	/* __KERNEL__ */
 
 extern void	xfs_mod_sb(struct xfs_trans *, __int64_t);