gfs2: Only access gl_delete for iopen glocks

Only initialize gl_delete for iopen glocks, but more importantly, only access
it for iopen glocks in flush_delete_work: flush_delete_work is called for
different types of glocks including rgrp glocks, and those use gl_vm which is
in a union with gl_delete.  Without this fix, we'll end up clobbering gl_vm,
which results in general memory corruption.

Fixes: a0e3cc65 ("gfs2: Turn gl_delete into a delayed work")
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glock.c

@@ -1051,7 +1051,8 @@ int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
 	gl->gl_object = NULL;
 	gl->gl_hold_time = GL_GLOCK_DFT_HOLD;
 	INIT_DELAYED_WORK(&gl->gl_work, glock_work_func);
-	INIT_DELAYED_WORK(&gl->gl_delete, delete_work_func);
+	if (gl->gl_name.ln_type == LM_TYPE_IOPEN)
+		INIT_DELAYED_WORK(&gl->gl_delete, delete_work_func);
 
 	mapping = gfs2_glock2aspace(gl);
 	if (mapping) {
@@ -1900,9 +1901,11 @@ bool gfs2_delete_work_queued(const struct gfs2_glock *gl)
 
 static void flush_delete_work(struct gfs2_glock *gl)
 {
-	if (cancel_delayed_work(&gl->gl_delete)) {
-		queue_delayed_work(gfs2_delete_workqueue,
-				   &gl->gl_delete, 0);
+	if (gl->gl_name.ln_type == LM_TYPE_IOPEN) {
+		if (cancel_delayed_work(&gl->gl_delete)) {
+			queue_delayed_work(gfs2_delete_workqueue,
+					   &gl->gl_delete, 0);
+		}
 	}
 	gfs2_glock_queue_work(gl, 0);
 }