staging: lustre: lov: ld_target could be NULL

lov_device::ld_target[ost_idx] could be NULL if the OST target is
not filled in lov_device::ld_lov::lov_tgt_desc[ost_idx] yet.
Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8018
Reviewed-on: http://review.whamcloud.com/21411Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/lov/lov_object.c

@@ -266,6 +266,13 @@ static int lov_init_raid0(const struct lu_env *env, struct lov_device *dev,
 			if (result != 0)
 				goto out;
 
+			if (!dev->ld_target[ost_idx]) {
+				CERROR("%s: OST %04x is not initialized\n",
+				lov2obd(dev->ld_lov)->obd_name, ost_idx);
+				result = -EIO;
+				goto out;
+			}
+
 			subdev = lovsub2cl_dev(dev->ld_target[ost_idx]);
 			subconf->u.coc_oinfo = oinfo;
 			LASSERTF(subdev, "not init ost %d\n", ost_idx);