nfsd: common grace period control

Rewrite grace period code to unify management of grace period across
lockd and nfsd.  The current code has lockd and nfsd cooperate to
compute a grace period which is satisfactory to them both, and then
individually enforce it.  This creates a slight race condition, since
the enforcement is not coordinated.  It's also more complicated than
necessary.

Here instead we have lockd and nfsd each inform common code when they
enter the grace period, and when they're ready to leave the grace
period, and allow normal locking only after both of them are ready to
leave.

We also expect the locks_start_grace()/locks_end_grace() interface here
to be simpler to build on for future cluster/high-availability work,
which may require (for example) putting individual filesystems into
grace, or enforcing grace periods across multiple cluster nodes.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 5 insertions, 15 deletions

diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index f345ef7..f013aed 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -51,7 +51,6 @@ static DEFINE_MUTEX(nlmsvc_mutex);
 static unsigned int		nlmsvc_users;
 static struct task_struct	*nlmsvc_task;
 static struct svc_rqst		*nlmsvc_rqst;
-int				nlmsvc_grace_period;
 unsigned long			nlmsvc_timeout;
 
 /*
@@ -85,30 +84,21 @@ static unsigned long get_lockd_grace_period(void)
 		return nlm_timeout * 5 * HZ;
 }
 
-unsigned long get_nfs_grace_period(void)
-{
-	unsigned long lockdgrace = get_lockd_grace_period();
-	unsigned long nfsdgrace = 0;
-
-	if (nlmsvc_ops)
-		nfsdgrace = nlmsvc_ops->get_grace_period();
-
-	return max(lockdgrace, nfsdgrace);
-}
-EXPORT_SYMBOL(get_nfs_grace_period);
+static struct lock_manager lockd_manager = {
+};
 
 static void grace_ender(struct work_struct *not_used)
 {
-	nlmsvc_grace_period = 0;
+	locks_end_grace(&lockd_manager);
 }
 
 static DECLARE_DELAYED_WORK(grace_period_end, grace_ender);
 
 static void set_grace_period(void)
 {
-	unsigned long grace_period = get_nfs_grace_period() + jiffies;
+	unsigned long grace_period = get_lockd_grace_period();
 
-	nlmsvc_grace_period = 1;
+	locks_start_grace(&lockd_manager);
 	cancel_delayed_work_sync(&grace_period_end);
 	schedule_delayed_work(&grace_period_end, grace_period);
 }