[PATCH] knfsd: nfsd4: create separate laundromat workqueue

We're running the laundromat work on the default kevent worker thread.  But
the laundromat takes the nfsv4 state semaphore, which is used for way too much
stuff, and the potential for deadlocks is high.  Better to have this on a
separate workqueue.
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: NNeil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/nfsd/nfs4state.c

@@ -1844,6 +1844,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
 	return status;
 }
 
+static struct workqueue_struct *laundry_wq;
 static struct work_struct laundromat_work;
 static void laundromat_main(void *);
 static DECLARE_WORK(laundromat_work, laundromat_main, NULL);
@@ -1951,7 +1952,7 @@ laundromat_main(void *not_used)
 
 	t = nfs4_laundromat();
 	dprintk("NFSD: laundromat_main - sleeping for %ld seconds\n", t);
-	schedule_delayed_work(&laundromat_work, t*HZ);
+	queue_delayed_work(laundry_wq, &laundromat_work, t*HZ);
 }
 
 /* search ownerid_hashtbl[] and close_lru for stateid owner
@@ -3211,7 +3212,8 @@ __nfs4_state_init(void)
 		printk("NFSD: starting %ld-second grace period\n", grace_time);
 	grace_end = boot_time + grace_time;
 	INIT_WORK(&laundromat_work,laundromat_main, NULL);
-	schedule_delayed_work(&laundromat_work, NFSD_LEASE_TIME*HZ);
+	laundry_wq = create_singlethread_workqueue("nfsd4");
+	queue_delayed_work(laundry_wq, &laundromat_work, NFSD_LEASE_TIME*HZ);
 }
 
 int
@@ -3287,7 +3289,8 @@ __nfs4_state_shutdown(void)
 	}
 
 	cancel_delayed_work(&laundromat_work);
-	flush_scheduled_work();
+	flush_workqueue(laundry_wq);
+	destroy_workqueue(laundry_wq);
 	nfs4_init = 0;
 }