[PATCH] knfsd: nfsd4: fix laundromat shutdown race

We need to make sure the laundromat work doesn't reschedule itself just when
we try to cancel it.  Also, we shouldn't be waiting for it to finish running
while holding the state lock, as that's a potential deadlock.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/nfs4state.c

@@ -3238,8 +3238,6 @@ __nfs4_state_shutdown(void)
 	}
 
 	cancel_delayed_work(&laundromat_work);
-	flush_workqueue(laundry_wq);
-	destroy_workqueue(laundry_wq);
 	nfsd4_shutdown_recdir();
 	nfs4_init = 0;
 }
@@ -3247,6 +3245,8 @@ __nfs4_state_shutdown(void)
 void
 nfs4_state_shutdown(void)
 {
+	cancel_rearming_delayed_workqueue(laundry_wq, &laundromat_work);
+	destroy_workqueue(laundry_wq);
 	nfs4_lock_state();
 	nfs4_release_reclaim();
 	__nfs4_state_shutdown();