Add path handling for aux vdevs in label_path

If the AUX vdev is added using UUID, importing the pool falls back AUX
vdev to open it with disk name instead of UUID due to the absence of
path information for AUX vdevs. Since AUX label now have path
information, this PR adds path handling for it in `label_path`.

Signed-off-by: Ameer Hamza <[email protected]>

lib/libzutil/zutil_import.c

@@ -1210,13 +1210,32 @@ label_paths(libpc_handle_t *hdl, nvlist_t *label, const char **path,
 	nvlist_t *nvroot;
 	uint64_t pool_guid;
 	uint64_t vdev_guid;
+	uint64_t state;
+	int is_aux = ((nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
+	    &state) == 0) && (state == POOL_STATE_SPARE ||
+	    state == POOL_STATE_L2CACHE));
 
 	*path = NULL;
 	*devid = NULL;
 
+	/*
+	 * In case of spare or l2cache, we directly return path/devid from the
+	 * label.
+	 */
+	if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &vdev_guid) == 0) {
+		if (is_aux) {
+			(void) nvlist_lookup_string(label, ZPOOL_CONFIG_PATH,
+			    path);
+			(void) nvlist_lookup_string(label, ZPOOL_CONFIG_DEVID,
+			    devid);
+			return (0);
+		}
+	} else {
+		return (ENOENT);
+	}
+
 	if (nvlist_lookup_nvlist(label, ZPOOL_CONFIG_VDEV_TREE, &nvroot) ||
-	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &pool_guid) ||
-	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &vdev_guid))
+	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &pool_guid))
 		return (ENOENT);
 
 	return (label_paths_impl(hdl, nvroot, pool_guid, vdev_guid, path,