GFS2: Allow flocks to use normal glock dq rather than dq_wait

This patch allows flock glocks to use a non-blocking dequeue rather
than dq_wait. It also reverts the previous patch I had posted regarding
dq_wait. The reverted patch isn't necessarily a bad idea, but I decided
this might avoid unforeseen side effects, and was therefore safer.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/file.c

@@ -991,7 +991,7 @@ static int do_flock(struct file *file, int cmd, struct file_lock *fl)
 			goto out;
 		flock_lock_file_wait(file,
 				     &(struct file_lock){.fl_type = F_UNLCK});
-		gfs2_glock_dq_wait(fl_gh);
+		gfs2_glock_dq(fl_gh);
 		gfs2_holder_reinit(state, flags, fl_gh);
 	} else {
 		error = gfs2_glock_get(GFS2_SB(&ip->i_inode), ip->i_no_addr,

fs/gfs2/glock.c

@@ -1128,9 +1128,7 @@ void gfs2_glock_dq_wait(struct gfs2_holder *gh)
 	struct gfs2_glock *gl = gh->gh_gl;
 	gfs2_glock_dq(gh);
 	might_sleep();
-	if (!find_first_holder(gl))
-		wait_on_bit(&gl->gl_flags, GLF_DEMOTE, gfs2_glock_demote_wait,
-			    TASK_UNINTERRUPTIBLE);
+	wait_on_bit(&gl->gl_flags, GLF_DEMOTE, gfs2_glock_demote_wait, TASK_UNINTERRUPTIBLE);
 }
 
 /**