GFS2: Reinstate withdraw ack system

This patch reinstates the ack system which withdraw should be using. It
appears to have been accidentally forgotten when the lock module was
merged into GFS2, due to two different sysfs files having the same name.

Reported-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/sys.c

@@ -330,6 +330,28 @@ static ssize_t block_store(struct gfs2_sbd *sdp, const char *buf, size_t len)
 	return ret;
 }
 
+static ssize_t wdack_show(struct gfs2_sbd *sdp, char *buf)
+{
+	int val = completion_done(&sdp->sd_wdack) ? 1 : 0;
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t wdack_store(struct gfs2_sbd *sdp, const char *buf, size_t len)
+{
+	ssize_t ret = len;
+	int val;
+
+	val = simple_strtol(buf, NULL, 0);
+
+	if ((val == 1) &&
+	    !strcmp(sdp->sd_lockstruct.ls_ops->lm_proto_name, "lock_dlm"))
+		complete(&sdp->sd_wdack);
+	else
+		ret = -EINVAL;
+	return ret;
+}
+
 static ssize_t lkfirst_show(struct gfs2_sbd *sdp, char *buf)
 {
 	struct lm_lockstruct *ls = &sdp->sd_lockstruct;
@@ -461,7 +483,7 @@ static struct gfs2_attr gdlm_attr_##_name = __ATTR(_name,_mode,_show,_store)
 
 GDLM_ATTR(proto_name,		0444, proto_name_show,		NULL);
 GDLM_ATTR(block,		0644, block_show,		block_store);
-GDLM_ATTR(withdraw,		0644, withdraw_show,		withdraw_store);
+GDLM_ATTR(withdraw,		0644, wdack_show,		wdack_store);
 GDLM_ATTR(jid,			0644, jid_show,			jid_store);
 GDLM_ATTR(first,		0644, lkfirst_show,		lkfirst_store);
 GDLM_ATTR(first_done,		0444, first_done_show,		NULL);