Iterate encrypted clones at zvol_create_minor

Userland figures out which encryption-root keys are required to load,
and issues ZFS_IOC_LOAD_KEY. The tail section of spa_keystore_load_wkey()
will call zvol_create_minors() on the encryption-root object.

Any clones of the encrypted zvol will not be plumbed. This commits
adds additional logic to detect if zvol has clones, and is encrypted,
then adds these to the list of zvols to call zvol_create_minors() on.

Signed-off-by: Jorgen Lundman <[email protected]>

module/zfs/zvol.c

@@ -1040,6 +1040,68 @@ 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);
+
+			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
  */
@@ -1078,6 +1140,8 @@ 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,