xfs: xfs_dquot prealloc throttling watermarks and low free space

Enable tracking of high and low watermarks for preallocation
throttling of files under quota restrictions. These values are
calculated when the quota limit is read from disk or modified and
cached for later use by the throttling algorithm.

The high watermark specifies when preallocation is disabled, the
low watermark specifies when throttling is enabled and the low free
space data structure contains precalculated low free space limits
to serve as input to determine the level of throttling required.

Note that the low free space data structure is based on the
existing global low free space data structure with the exception of
using three stages (5%, 3% and 1%) rather than five to reduce the
impact of xfs_dquot memory overhead.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_qm.h b/fs/xfs/xfs_qm.h
index 44b858b..82c2108 100644
--- a/fs/xfs/xfs_qm.h
+++ b/fs/xfs/xfs_qm.h
@@ -116,7 +116,7 @@
 extern int		xfs_qm_scall_trunc_qfiles(xfs_mount_t *, uint);
 extern int		xfs_qm_scall_getquota(xfs_mount_t *, xfs_dqid_t, uint,
 					fs_disk_quota_t *);
-extern int		xfs_qm_scall_setqlim(xfs_mount_t *, xfs_dqid_t, uint,
+extern int		xfs_qm_scall_setqlim(struct xfs_mount *, xfs_dqid_t, uint,
 					fs_disk_quota_t *);
 extern int		xfs_qm_scall_getqstat(xfs_mount_t *, fs_quota_stat_t *);
 extern int		xfs_qm_scall_quotaon(xfs_mount_t *, uint);