Storage device expansion "silently" fails on degraded vdev

When a vdev is degraded or faulted, we refuse to expand it when doing
online -e. However, we also don't actually cause the online command
to fail, even though the disk didn't expand. This is confusing and
misleading, and can result in violated expectations.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes 14145

cmd/zpool/zpool_main.c

@@ -6933,6 +6933,17 @@ zpool_do_online(int argc, char **argv)
 		return (1);
 
 	for (i = 1; i < argc; i++) {
+		vdev_state_t oldstate;
+		boolean_t avail_spare, l2cache;
+		nvlist_t *tgt = zpool_find_vdev(zhp, argv[i], &avail_spare,
+		    &l2cache, NULL);
+		if (tgt == NULL) {
+			ret = 1;
+			continue;
+		}
+		uint_t vsc;
+		oldstate = ((vdev_stat_t *)fnvlist_lookup_uint64_array(tgt,
+		    ZPOOL_CONFIG_VDEV_STATS, &vsc))->vs_state;
 		if (zpool_vdev_online(zhp, argv[i], flags, &newstate) == 0) {
 			if (newstate != VDEV_STATE_HEALTHY) {
 				(void) printf(gettext("warning: device '%s' "
@@ -6946,6 +6957,17 @@ zpool_do_online(int argc, char **argv)
 					(void) printf(gettext("use 'zpool "
 					    "replace' to replace devices "
 					    "that are no longer present\n"));
+				if ((flags & ZFS_ONLINE_EXPAND)) {
+					(void) printf(gettext("%s: failed "
+					    "to expand usable space on "
+					    "unhealthy device '%s'\n"),
+					    (oldstate >= VDEV_STATE_DEGRADED ?
+					    "error" : "warning"), argv[i]);
+					if (oldstate >= VDEV_STATE_DEGRADED) {
+						ret = 1;
+						break;
+					}
+				}
 			}
 		} else {
 			ret = 1;