Fix unfortunate NULL in spa_update_dspace

After 1325434, we can in certain circumstances end up calling spa_update_dspace with vd->vdev_mg NULL, which ends poorly during vdev removal. So let's not do that further space adjustment when we can't. Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Rich Ercolani <[email protected]> Closes openzfs#12380 Closes openzfs#12428
behlendorf · Aug 23, 2021 · 6ec713c · 6ec713c
1 parent 2a15707
commit 6ec713c
Showing 1 changed file with 8 additions and 1 deletion.
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
@@ -1868,7 +1868,14 @@ spa_update_dspace(spa_t *spa)
 		spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
 		vdev_t *vd =
 		    vdev_lookup_top(spa, spa->spa_vdev_removal->svr_vdev_id);
-		if (vd->vdev_mg->mg_class == spa_normal_class(spa)) {
+		/*
+		 * If the stars align, we can wind up here after
+		 * vdev_remove_complete() has cleared vd->vdev_mg but before
+		 * spa->spa_vdev_removal gets cleared, so we must check before
+		 * we dereference.
+		 */
+		if (vd->vdev_mg &&
+		    vd->vdev_mg->mg_class == spa_normal_class(spa)) {
 			spa->spa_dspace -= spa_deflate(spa) ?
 			    vd->vdev_stat.vs_dspace : vd->vdev_stat.vs_space;
 		}