Fix pool creation with feature@allocation_classes disabled

When "feature@allocation_classes" is not enabled on the pool no vdev
with "special" or "dedup" allocation type should be allowed to exist in
the vdev tree.

Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #9427 
Closes #9429

include/zfs_comutil.h

@@ -34,6 +34,7 @@ extern "C" {
 #endif
 
 extern boolean_t zfs_allocatable_devs(nvlist_t *);
+extern boolean_t zfs_special_devs(nvlist_t *);
 extern void zpool_get_load_policy(nvlist_t *, zpool_load_policy_t *);
 
 extern int zfs_zpl_version_map(int spa_version);

module/zcommon/zfs_comutil.c

@@ -64,6 +64,33 @@ zfs_allocatable_devs(nvlist_t *nv)
 	return (B_FALSE);
 }
 
+/*
+ * Are there special vdevs?
+ */
+boolean_t
+zfs_special_devs(nvlist_t *nv)
+{
+	char *bias;
+	uint_t c;
+	nvlist_t **child;
+	uint_t children;
+
+	if (nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
+	    &child, &children) != 0) {
+		return (B_FALSE);
+	}
+	for (c = 0; c < children; c++) {
+		if (nvlist_lookup_string(child[c], ZPOOL_CONFIG_ALLOCATION_BIAS,
+		    &bias) == 0) {
+			if (strcmp(bias, VDEV_ALLOC_BIAS_SPECIAL) == 0 ||
+			    strcmp(bias, VDEV_ALLOC_BIAS_DEDUP) == 0) {
+				return (B_TRUE);
+			}
+		}
+	}
+	return (B_FALSE);
+}
+
 void
 zpool_get_load_policy(nvlist_t *nvl, zpool_load_policy_t *zlpp)
 {
@@ -223,6 +250,7 @@ zfs_dataset_name_hidden(const char *name)
 
 #if defined(_KERNEL)
 EXPORT_SYMBOL(zfs_allocatable_devs);
+EXPORT_SYMBOL(zfs_special_devs);
 EXPORT_SYMBOL(zpool_get_load_policy);
 EXPORT_SYMBOL(zfs_zpl_version_map);
 EXPORT_SYMBOL(zfs_spa_version_map);

module/zfs/spa.c

@@ -5620,6 +5620,7 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 	uint64_t version, obj;
 	boolean_t has_features;
 	boolean_t has_encryption;
+	boolean_t has_allocclass;
 	spa_feature_t feat;
 	char *feat_name;
 	char *poolname;
@@ -5664,6 +5665,7 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 
 	has_features = B_FALSE;
 	has_encryption = B_FALSE;
+	has_allocclass = B_FALSE;
 	for (nvpair_t *elem = nvlist_next_nvpair(props, NULL);
 	    elem != NULL; elem = nvlist_next_nvpair(props, elem)) {
 		if (zpool_prop_feature(nvpair_name(elem))) {
@@ -5673,6 +5675,8 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 			VERIFY0(zfeature_lookup_name(feat_name, &feat));
 			if (feat == SPA_FEATURE_ENCRYPTION)
 				has_encryption = B_TRUE;
+			if (feat == SPA_FEATURE_ALLOCATION_CLASSES)
+				has_allocclass = B_TRUE;
 		}
 	}
 
@@ -5686,6 +5690,12 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 			return (error);
 		}
 	}
+	if (!has_allocclass && zfs_special_devs(nvroot)) {
+		spa_deactivate(spa);
+		spa_remove(spa);
+		mutex_exit(&spa_namespace_lock);
+		return (ENOTSUP);
+	}
 
 	if (has_features || nvlist_lookup_uint64(props,
 	    zpool_prop_to_name(ZPOOL_PROP_VERSION), &version) != 0) {

tests/zfs-tests/tests/functional/alloc_class/alloc_class_001_pos.ksh

@@ -20,7 +20,8 @@
 
 #
 # DESCRIPTION:
-#	Creating a pool with a special device succeeds.
+#	Creating a pool with a special device succeeds, but only if
+#	"feature@allocation_classes" is enabled.
 #
 
 verify_runnable "global"
@@ -31,6 +32,9 @@ log_assert $claim
 log_onexit cleanup
 
 log_must disk_setup
+for type in special dedup; do
+	log_mustnot zpool create -d $TESTPOOL $CLASS_DISK0 $type $CLASS_DISK1
+done
 log_must zpool create $TESTPOOL raidz $ZPOOL_DISKS special mirror \
     $CLASS_DISK0 $CLASS_DISK1
 log_must display_status "$TESTPOOL"