Upstream: iterate encrypted clones at create_minor

After key loaded, zvol_create_minors_recursive() is called on the
specific zvol, but not on any clones also using the key.

Add function to detect encryption, and clones, then add those
to the list of zvols to call zvol_os_create_minor() on.

module/zfs/zvol.c

@@ -1039,6 +1039,68 @@ zvol_create_snap_minor_cb(const char *dsname, void *arg)
 	return (0);
 }
 
+/*
+ * If spa_keystore_load_wkey() is called for an encrypted zvol,
+ * we need to look for any clones also using the key. This function
+ * is "best effort" - so we just skip over it if there are failures.
+ */
+static void
+zvol_add_clones(const char *dsname, list_t *minors_list)
+{
+	/* Also check if it has clones */
+	dsl_dir_t *dd = NULL;
+	dsl_pool_t *dp = NULL;
+
+	if (dsl_pool_hold(dsname, FTAG, &dp) != 0)
+		return;
+
+	if (!spa_feature_is_enabled(dp->dp_spa,
+	    SPA_FEATURE_ENCRYPTION))
+		goto out;
+
+	if (dsl_dir_hold(dp, dsname, FTAG, &dd, NULL) != 0)
+		goto out;
+
+	if (dsl_dir_phys(dd)->dd_clones == 0)
+		goto out;
+
+	zap_cursor_t *zc = kmem_alloc(sizeof (zap_cursor_t), KM_SLEEP);
+	zap_attribute_t *za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
+	objset_t *mos = dd->dd_pool->dp_meta_objset;
+
+	for (zap_cursor_init(zc, mos, dsl_dir_phys(dd)->dd_clones);
+	    zap_cursor_retrieve(zc, za) == 0;
+	    zap_cursor_advance(zc)) {
+		dsl_dataset_t *clone;
+		minors_job_t *job;
+
+		if (dsl_dataset_hold_obj(dd->dd_pool,
+		    za->za_first_integer, FTAG, &clone) == 0) {
+
+			char name[ZFS_MAX_DATASET_NAME_LEN];
+			dsl_dataset_name(clone, name);
+			printf("adding clone '%s'\n", name);
+			char *n = kmem_strdup(name);
+			job = kmem_alloc(sizeof (minors_job_t), KM_SLEEP);
+			job->name = n;
+			job->list = minors_list;
+			job->error = 0;
+			list_insert_tail(minors_list, job);
+
+			dsl_dataset_rele(clone, FTAG);
+		}
+	}
+	zap_cursor_fini(zc);
+	kmem_free(za, sizeof (zap_attribute_t));
+	kmem_free(zc, sizeof (zap_cursor_t));
+
+out:
+	if (dd != NULL)
+		dsl_dir_rele(dd, FTAG);
+	if (dp != NULL)
+		dsl_pool_rele(dp, FTAG);
+}
+
 /*
  * Mask errors to continue dmu_objset_find() traversal
  */
@@ -1077,6 +1139,8 @@ zvol_create_minors_cb(const char *dsname, void *arg)
 		taskq_dispatch(system_taskq, zvol_prefetch_minors_impl, job,
 		    TQ_SLEEP);
 
+		zvol_add_clones(dsname, minors_list);
+
 		if (snapdev == ZFS_SNAPDEV_VISIBLE) {
 			/*
 			 * traverse snapshots only, do not traverse children,