On 7/11/22 16:28, Damien Le Moal wrote:
On 7/12/22 08:11, Damien Le Moal wrote:
On 7/12/22 08:00, Bart Van Assche wrote:
Using the RETURNED LOGICAL BLOCK ADDRESS field + 1 as the capacity (largest
addressable LBA) if RC BASIS = 0 is wrong if there are sequential write
required zones. Hence only use the RC BASIS = 0 capacity if there are no
sequential write required zones.
This does not make sense to me: RC BASIS == 0 is defined like this:
The RETURNED LOGICAL BLOCK ADDRESS field indicates the highest LBA of a
contiguous range of zones that are not sequential write required zones
starting with the first zone.
Do you have these cases:
1) host-managed disks:
SWR zones are *mandatory* so there is at least one. Thus read capacity
will return either 0 if there are no conventional zones (they are
optional) or the total capacity of the set of contiguous conventional
zones starting at lba 0. In either case, read capacity does not give you
the actual total capacity and you have to look at the report zones reply
max lba field.
2) host-aware disks:
There are no SWR zones, there cannot be any. You can only have
conventional zones (optionally) and sequential write preferred zones. So
"the highest LBA of a contiguous range of zones that are not sequential
write required zones starting with the first zone" necessarily is always
the total capacity. RC BASIS = 0 is non-sensical for host-aware drives.
What I meant to say here for the host-aware case is that RC BASIS is
irrelevant. Both RC BASIS = 0 and = 1 end up with read capacity giving the
actual total capacity. ANd for good reasons: the host-aware model is
designed to be backward compatible with regular disks, which do not have
RC BASIS, so RC BASIS = 0, always.
Hi Damien,
I agree that for host-aware block devices (conventional + sequential write
preferred zones) RC BASIS is irrelevant.
What I'm concerned about is host-managed block devices (conventional + sequential
write required zones) that report an incorrect RC BASIS value (0 instead of 1).
Shouldn't sd_zbc_check_capacity() skip the capacity reported by host-managed block
devices that report RC BASIS = 0?
Thanks,
Bart.
