There's no real reason not to enable it always; the `zfs` command always
enables it anyway, and right now there's multiple places that do mount
work that don't go through the cache anyway. Having it always be on lets
us remove a bunch of the fallback code.
Sponsored-by: TrueNAS
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@truenas.com>
Closes#18296
0ecf5e3f62