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>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 1533cf8..e2601ba 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -642,6 +642,7 @@
 	wait_queue_head_t sd_glock_wait;
 	atomic_t sd_glock_disposal;
 	struct completion sd_locking_init;
+	struct completion sd_wdack;
 	struct delayed_work sd_control_work;
 
 	/* Inode Stuff */
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index e063f22..1b612be 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -81,6 +81,7 @@
 	init_waitqueue_head(&sdp->sd_glock_wait);
 	atomic_set(&sdp->sd_glock_disposal, 0);
 	init_completion(&sdp->sd_locking_init);
+	init_completion(&sdp->sd_wdack);
 	spin_lock_init(&sdp->sd_statfs_spin);
 
 	spin_lock_init(&sdp->sd_rindex_spin);
diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c
index 462e841..4fb9ad8 100644
--- a/fs/gfs2/sys.c
+++ b/fs/gfs2/sys.c
@@ -330,6 +330,28 @@
 	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 @@
 
 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);
diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c
index f00d7c5..6402fb6 100644
--- a/fs/gfs2/util.c
+++ b/fs/gfs2/util.c
@@ -54,6 +54,9 @@
 
 		kobject_uevent(&sdp->sd_kobj, KOBJ_OFFLINE);
 
+		if (!strcmp(sdp->sd_lockstruct.ls_ops->lm_proto_name, "lock_dlm"))
+			wait_for_completion(&sdp->sd_wdack);
+
 		if (lm->lm_unmount) {
 			fs_err(sdp, "telling LM to unmount\n");
 			lm->lm_unmount(sdp);