LU-12335 ldiskfs: fixed size preallocation table

LU-12335 ldiskfs: fixed size preallocation table

Preallocation table read/write code is racy. There is a
possibility of accessing memory outside of allocated table.

Make preallocation table fixed size. Array with 64
long int values are enough for any configuration and
don’t need much memory. With such array races are not
possible.

Signed-off-by: Artem Blagodarenko <c17828@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Reviewed-by: Alexander Zarochentsev <c17826@cray.com>
Tested-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-7218
Change-Id: Ie089ac47c2610717a00d6cea9121ec08879a159c
Reviewed-on: https://review.whamcloud.com/34950
Tested-by: Jenkins
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>