Create zap for root vdev

And add it to the AVZ, this is not backwards compatible with older pools
due to an assertion in spa_sync() that verifies the number of ZAPs of
all vdevs matches the number of ZAPs in the AVZ.

Granted, the assertion only applies to #DEBUG builds - still, a feature
flag is introduced to avoid the assertion, com.klarasystems:vdev_zaps_v2

Notably, this allows to get/set properties on the root vdev:

    % zpool set user:prop=value <pool> root-0

Before this commit, it was already possible to get/set properties on
top-level vdevs with the syntax <type>-<vdev_id> (e.g. mirror-0):

    % zpool set user:prop=value <pool> mirror-0

This syntax also applies to the root vdev as it is is of type 'root'
with a vdev_id of 0, root-0. The keyword 'root' as an alias for
'root-0'.

The following tests have been added:

    - zpool get all properties from root vdev
    - zpool set a property on root vdev
    - verify root vdev ZAP is created

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Wing <rob.wing@klarasystems.com>
Sponsored-by: Seagate Technology
Submitted-by: Klara, Inc.
Closes #14405

cmd/zpool/zpool_main.c

@@ -10001,33 +10001,33 @@ get_callback_vdev(zpool_handle_t *zhp, char *vdevname, void *data)
 	return (0);
 }
 
-static int
-get_callback_vdev_width_cb(void *zhp_data, nvlist_t *nv, void *data)
-{
-	zpool_handle_t *zhp = zhp_data;
-	zprop_get_cbdata_t *cbp = (zprop_get_cbdata_t *)data;
-	char *vdevname = zpool_vdev_name(g_zfs, zhp, nv,
-	    cbp->cb_vdevs.cb_name_flags);
-	int ret;
-
-	/* Adjust the column widths for the vdev properties */
-	ret = vdev_expand_proplist(zhp, vdevname, &cbp->cb_proplist);
-
-	return (ret);
-}
-
 static int
 get_callback_vdev_cb(void *zhp_data, nvlist_t *nv, void *data)
 {
 	zpool_handle_t *zhp = zhp_data;
 	zprop_get_cbdata_t *cbp = (zprop_get_cbdata_t *)data;
-	char *vdevname = zpool_vdev_name(g_zfs, zhp, nv,
-	    cbp->cb_vdevs.cb_name_flags);
+	char *vdevname;
+	const char *type;
 	int ret;
 
-	/* Display the properties */
+	/*
+	 * zpool_vdev_name() transforms the root vdev name (i.e., root-0) to the
+	 * pool name for display purposes, which is not desired. Fallback to
+	 * zpool_vdev_name() when not dealing with the root vdev.
+	 */
+	type = fnvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE);
+	if (zhp != NULL && strcmp(type, "root") == 0)
+		vdevname = strdup("root-0");
+	else
+		vdevname = zpool_vdev_name(g_zfs, zhp, nv,
+		    cbp->cb_vdevs.cb_name_flags);
+
+	(void) vdev_expand_proplist(zhp, vdevname, &cbp->cb_proplist);
+
 	ret = get_callback_vdev(zhp, vdevname, data);
 
+	free(vdevname);
+
 	return (ret);
 }
 
@@ -10042,7 +10042,6 @@ get_callback(zpool_handle_t *zhp, void *data)
 
 	if (cbp->cb_type == ZFS_TYPE_VDEV) {
 		if (strcmp(cbp->cb_vdevs.cb_names[0], "all-vdevs") == 0) {
-			for_each_vdev(zhp, get_callback_vdev_width_cb, data);
 			for_each_vdev(zhp, get_callback_vdev_cb, data);
 		} else {
 			/* Adjust column widths for vdev properties */
@@ -10119,6 +10118,7 @@ zpool_do_get(int argc, char **argv)
 	int ret;
 	int c, i;
 	char *propstr = NULL;
+	char *vdev = NULL;
 
 	cb.cb_first = B_TRUE;
 
@@ -10216,10 +10216,17 @@ found:
 	} else if (are_all_pools(1, argv)) {
 		/* The first arg is a pool name */
 		if ((argc == 2 && strcmp(argv[1], "all-vdevs") == 0) ||
+		    (argc == 2 && strcmp(argv[1], "root") == 0) ||
 		    are_vdevs_in_pool(argc - 1, argv + 1, argv[0],
 		    &cb.cb_vdevs)) {
+
+			if (strcmp(argv[1], "root") == 0)
+				vdev = strdup("root-0");
+			else
+				vdev = strdup(argv[1]);
+
 			/* ... and the rest are vdev names */
-			cb.cb_vdevs.cb_names = argv + 1;
+			cb.cb_vdevs.cb_names = &vdev;
 			cb.cb_vdevs.cb_names_count = argc - 1;
 			cb.cb_type = ZFS_TYPE_VDEV;
 			argc = 1; /* One pool to process */
@@ -10264,6 +10271,9 @@ found:
 	else
 		zprop_free_list(cb.cb_proplist);
 
+	if (vdev != NULL)
+		free(vdev);
+
 	return (ret);
 }
 
@@ -10365,6 +10375,7 @@ zpool_do_set(int argc, char **argv)
 {
 	set_cbdata_t cb = { 0 };
 	int error;
+	char *vdev = NULL;
 
 	current_prop_type = ZFS_TYPE_POOL;
 	if (argc > 1 && argv[1][0] == '-') {
@@ -10413,13 +10424,20 @@ zpool_do_set(int argc, char **argv)
 
 	/* argv[1], when supplied, is vdev name */
 	if (argc == 2) {
-		if (!are_vdevs_in_pool(1, argv + 1, argv[0], &cb.cb_vdevs)) {
+
+		if (strcmp(argv[1], "root") == 0)
+			vdev = strdup("root-0");
+		else
+			vdev = strdup(argv[1]);
+
+		if (!are_vdevs_in_pool(1, &vdev, argv[0], &cb.cb_vdevs)) {
 			(void) fprintf(stderr, gettext(
 			    "cannot find '%s' in '%s': device not in pool\n"),
-			    argv[1], argv[0]);
+			    vdev, argv[0]);
+			free(vdev);
 			return (EINVAL);
 		}
-		cb.cb_vdevs.cb_names = argv + 1;
+		cb.cb_vdevs.cb_names = &vdev;
 		cb.cb_vdevs.cb_names_count = 1;
 		cb.cb_type = ZFS_TYPE_VDEV;
 	}
@@ -10427,6 +10445,9 @@ zpool_do_set(int argc, char **argv)
 	error = for_each_pool(1, argv, B_TRUE, NULL, ZFS_TYPE_POOL,
 	    B_FALSE, set_callback, &cb);
 
+	if (vdev != NULL)
+		free(vdev);
+
 	return (error);
 }