Revert "Check for SPA_FEATURE_DRAID_FAIL_DOMAINS at vdev_alloc()"

This should allow addition of new draids without failure domains
on legacy (not upgraded) pools.

This reverts commit 37e02d1.

Author: andriytk

module/zfs/spa.c

@@ -6895,6 +6895,10 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 	for (int i = 0; i < ndraid; i++)
 		spa_feature_incr(spa, SPA_FEATURE_DRAID, tx);
 
+	if (!spa_feature_is_enabled(spa, SPA_FEATURE_DRAID_FAIL_DOMAINS) &&
+	    draid_nfgroup > 0)
+		return (SET_ERROR(ENOTSUP));
+
 	for (int i = 0; i < draid_nfgroup; i++)
 		spa_feature_incr(spa, SPA_FEATURE_DRAID_FAIL_DOMAINS, tx);
 
@@ -7643,6 +7647,10 @@ spa_vdev_add(spa_t *spa, nvlist_t *nvroot, boolean_t check_ashift)
 		dsl_sync_task_nowait(spa->spa_dsl_pool, spa_draid_feature_incr,
 		    (void *)(uintptr_t)ndraid, tx);
 
+		if (!spa_feature_is_enabled(spa,
+		    SPA_FEATURE_DRAID_FAIL_DOMAINS) && draid_nfgroup > 0)
+			return (spa_vdev_exit(spa, vd, txg, ENOTSUP));
+
 		if (draid_nfgroup > 0)
 			dsl_sync_task_nowait(spa->spa_dsl_pool,
 			    spa_draid_fdomains_feature_incr,

module/zfs/vdev.c

@@ -903,14 +903,6 @@ vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent, uint_t id,
 		    !spa_feature_is_enabled(spa, SPA_FEATURE_DRAID)) {
 			return (SET_ERROR(ENOTSUP));
 		}
-
-		/* spa_vdev_add() expects feature to be enabled */
-		if (ops == &vdev_draid_ops &&
-		    spa->spa_load_state != SPA_LOAD_CREATE &&
-		    !spa_feature_is_enabled(spa,
-		    SPA_FEATURE_DRAID_FAIL_DOMAINS))
-			return (SET_ERROR(ENOTSUP));
-
 	}
 
 	/*