hello ,
it seems useless to match uuid between rootfs partition and records in /etc/.extroot-uuid
in function check_extroot in block.c, i see that codes

if (*uuid || !strcasecmp(uuid, pr->uuid))
                  return 0;

it means that whether the uuid in .extroot-uuid matching rootfs's uuid or not ，it will return sucessfully if .extroot-uuid is not empty
how if i delete check_extroot?

is it nobody now?

Mmmm  only 1h, that's bold

Look like some error in a previous patch,
can you test ??

i modify it , codes as follows ( block.c - check_extroot() ) :

            if (*uuid && !strcasecmp(uuid, pr->uuid)) {
                  ULOG_ERR("extroot: UUID match (root: %s, %s: %s)\n",
                       pr->uuid, basename(path), uuid);
              } else {
                  ULOG_ERR("extroot: UUID mismatch (root: %s, %s: %s), but continue\n",
                       pr->uuid, basename(path), uuid);
              }
              return 0;

it only prints some notes and allway returns 0, then run , it seems all are ok even if  i delete /etc/.extroot-uuid or modify recorded id in it
so, what is the use of function  check_extroot?

it is funny that it was fix one day before my asking.
you can see in git.openwrt.org