fs/ocfs2/dlmfs: remove deprecated create_singlethread_workqueue()

The workqueue "user_dlm_worker" queues a single work item
&lockres->l_work per user_lock_res instance and so it doesn't require
execution ordering.  Hence, alloc_workqueue has been used to replace the
deprecated create_singlethread_workqueue instance.

The WQ_MEM_RECLAIM flag has been set to ensure forward progress under
memory pressure.

Since there are fixed number of work items, explicit concurrency
limit is unnecessary here.

Link: http://lkml.kernel.org/r/9748136d3a3b18138ad1d6ba708367aa1fe9f98c.1472590094.git.bhaktipriya96@gmail.comSigned-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/dlmfs/dlmfs.c

@@ -646,7 +646,7 @@ static int __init init_dlmfs_fs(void)
 	}
 	cleanup_inode = 1;
 
-	user_dlm_worker = create_singlethread_workqueue("user_dlm");
+	user_dlm_worker = alloc_workqueue("user_dlm", WQ_MEM_RECLAIM, 0);
 	if (!user_dlm_worker) {
 		status = -ENOMEM;
 		goto bail;