Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c8ab5f2a authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

lockd: don't depend on lockd main loop to end grace 



End lockd's grace period using schedule_delayed_work() instead of a
check on every pass through the main loop.

After a later patch, we'll depend on lockd to end its grace period even
if it's not currently handling requests; so it shouldn't depend on being
woken up from the main loop to do so.

Also, Nakano Hiroaki (who independently produced a similar patch)
noticed that the current behavior is buggy in the face of jiffies
wraparound:

	"lockd uses time_before() to determine whether the grace period
	has expired. This would seem to be enough to avoid timer
	wrap-around issues, but, unfortunately, that is not the case.
	The time_* family of comparison functions can be safely used to
	compare jiffies relatively close in time, but they stop working
	after approximately LONG_MAX/2 ticks. nfsd can suffer this
	problem because the time_before() comparison in lockd() is not
	performed until the first request comes in, which means that if
	there is no lockd traffic for more than LONG_MAX/2 ticks we are
	screwed.

	"The implication of this is that once time_before() starts
	misbehaving any attempt from a NFS client to execute fcntl()
	will be received with a NLM_LCK_DENIED_GRACE_PERIOD message for
	25 days (assuming HZ=1000). In other words, the 50 seconds grace
	period could turn into a grace period of 50 days or more.

	"Note: This bug was analyzed independently by Oda-san
	<oda@valinux.co.jp> and myself."

Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
Cc: Nakano Hiroaki <nakano.hiroaki@oss.ntt.co.jp>
Cc: Itsuro Oda <oda@valinux.co.jp>
parent 8fafa900

fs/lockd/svc.c

+13 −11
Original line number Diff line number Diff line
@@ -97,15 +97,20 @@ unsigned long get_nfs_grace_period(void) 
}

EXPORT_SYMBOL(get_nfs_grace_period);



static unsigned long set_grace_period(void)

static void grace_ender(struct work_struct *not_used)

{

	nlmsvc_grace_period = 1;

	return get_nfs_grace_period() + jiffies;

	nlmsvc_grace_period = 0;

}



static inline void clear_grace_period(void)

static DECLARE_DELAYED_WORK(grace_period_end, grace_ender);



static void set_grace_period(void)

{

	nlmsvc_grace_period = 0;

	unsigned long grace_period = get_nfs_grace_period() + jiffies;



	nlmsvc_grace_period = 1;

	cancel_delayed_work_sync(&grace_period_end);

	schedule_delayed_work(&grace_period_end, grace_period);

}



/*
@@ -116,7 +121,6 @@ lockd(void *vrqstp) 
{

	int		err = 0, preverr = 0;

	struct svc_rqst *rqstp = vrqstp;

	unsigned long grace_period_expire;



	/* try_to_freeze() is called from svc_recv() */

	set_freezable();
@@ -139,7 +143,7 @@ lockd(void *vrqstp) 
		nlm_timeout = LOCKD_DFLT_TIMEO;

	nlmsvc_timeout = nlm_timeout * HZ;



	grace_period_expire = set_grace_period();

	set_grace_period();



	/*

	 * The main request loop. We don't terminate until the last
@@ -153,16 +157,13 @@ lockd(void *vrqstp) 
			flush_signals(current);

			if (nlmsvc_ops) {

				nlmsvc_invalidate_all();

				grace_period_expire = set_grace_period();

				set_grace_period();

			}

			continue;

		}



		timeout = nlmsvc_retry_blocked();



		if (time_before(grace_period_expire, jiffies))

			clear_grace_period();



		/*

		 * Find a socket with data available and call its

		 * recvfrom routine.
@@ -189,6 +190,7 @@ lockd(void *vrqstp) 
		svc_process(rqstp);

	}

	flush_signals(current);

	cancel_delayed_work_sync(&grace_period_end);

	if (nlmsvc_ops)

		nlmsvc_invalidate_all();

	nlm_shutdown_hosts();