1693 persistent 'comment' field for a zpool

*** 233,242 ****
--- 233,243 ----
                          (void) snprintf(buf, len, "%llu", intval);
                          break;
  
                  case ZPOOL_PROP_ALTROOT:
                  case ZPOOL_PROP_CACHEFILE:
+                 case ZPOOL_PROP_COMMENT:
                          if (zhp->zpool_props != NULL ||
                              zpool_get_all_props(zhp) == 0) {
                                  (void) strlcpy(buf,
                                      zpool_get_prop_string(zhp, prop, &src),
                                      len);
*** 382,392 ****
          nvpair_t *elem;
          nvlist_t *retprops;
          zpool_prop_t prop;
          char *strval;
          uint64_t intval;
!         char *slash;
          struct stat64 statbuf;
          zpool_handle_t *zhp;
          nvlist_t *nvroot;
  
          if (nvlist_alloc(&retprops, NV_UNIQUE_NAME, 0) != 0) {
--- 383,393 ----
          nvpair_t *elem;
          nvlist_t *retprops;
          zpool_prop_t prop;
          char *strval;
          uint64_t intval;
!         char *slash, *check;
          struct stat64 statbuf;
          zpool_handle_t *zhp;
          nvlist_t *nvroot;
  
          if (nvlist_alloc(&retprops, NV_UNIQUE_NAME, 0) != 0) {
*** 541,550 ****
--- 542,571 ----
                          }
  
                          *slash = '/';
                          break;
  
+                 case ZPOOL_PROP_COMMENT:
+                         for (check = strval; *check != '\0'; check++) {
+                                 if (!isprint(*check)) {
+                                         zfs_error_aux(hdl,
+                                             dgettext(TEXT_DOMAIN,
+                                             "comment may only have printable "
+                                             "characters"));
+                                         (void) zfs_error(hdl, EZFS_BADPROP,
+                                             errbuf);
+                                         goto error;
+                                 }
+                         }
+                         if (strlen(strval) > ZPROP_MAX_COMMENT) {
+                                 zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+                                     "comment must not exceed %d characters"),
+                                     ZPROP_MAX_COMMENT);
+                                 (void) zfs_error(hdl, EZFS_BADPROP, errbuf);
+                                 goto error;
+                         }
+                         break;
                  case ZPOOL_PROP_READONLY:
                          if (!flags.import) {
                                  zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
                                      "property '%s' can only be set at "
                                      "import time"), propname);