md-cluster: make md-cluster also can work when compiled into kernel

The md-cluster is compiled as module by default,
if it is compiled by built-in way, then we can't
make md-cluster works.

[64782.630008] md/raid1:md127: active with 2 out of 2 mirrors
[64782.630528] md-cluster module not found.
[64782.630530] md127: Could not setup cluster service (-2)

Fixes: edb39c9 ("Introduce md_cluster_operations to handle cluster functions")
Cc: stable@vger.kernel.org (v4.1+)
Reported-by: Marc Smith <marc.smith@mcc.edu>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 4 insertions, 8 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 67642bacd597..915e84d631a2 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7610,16 +7610,12 @@ EXPORT_SYMBOL(unregister_md_cluster_operations);
 
 int md_setup_cluster(struct mddev *mddev, int nodes)
 {
-        int err;
-
-        err = request_module("md-cluster");
-        if (err) {
-                pr_err("md-cluster module not found.\n");
-                return -ENOENT;
-        }
-
+        if (!md_cluster_ops)
+                request_module("md-cluster");
         spin_lock(&pers_lock);
+        /* ensure module won't be unloaded */
         if (!md_cluster_ops || !try_module_get(md_cluster_mod)) {
+                pr_err("can't find md-cluster module or get it's reference.\n");
                 spin_unlock(&pers_lock);
                 return -ENOENT;
         }