Re: [Qemu-devel] [PATCHv7 00/17] block: logical block provisioning enhancements

[ronnie sahlberg]

For better support for older versions of libiscsi
I think it would be good to convert all the
iscsi_unmap_task/iscsi_writesame*_task/iscsi_*_task   functions with
calls to the much more genric iscsi_scsi_command_sync().

iscsi_scsi_command_sync() and iscsi_scsi_command_async() have been
available since prior to version 1.1 and can be used to send arbitrary
scsi opcodes to the target.


iscsi_scsi_command_async() is already used instead of
iscs_read16/write16_async() since the read16/write16 helpers were
added to libiscsi at a much later stage and there are examples of its
use.


Using iscsi_scsi_command_[a]sync() instead of for example
iscsi_unmap_task() would mean that you can use the UNMAP opcode
always, regardless version of libiscsi.
It would mean that you need to build the CDB directly inside
block/iscsi.c but that is not hard.


I.e.  change block/iscsi.c to only use iscsi_scsi_command_[a]sync()
for all opcodes it wants to send to the target.




On Wed, Nov 6, 2013 at 1:16 PM, Paolo Bonzini <address@hidden> wrote:
> Il 06/11/2013 20:38, Peter Lieven ha scritto:
>>
>> Am 06.11.2013 um 14:09 schrieb Paolo Bonzini <address@hidden>:
>>
>>> Il 06/11/2013 14:08, Stefan Hajnoczi ha scritto:
>>>> Thanks, applied to my block-next tree:
>>>> https://github.com/stefanha/qemu/commits/block-next
>>>>
>>>> This will go into QEMU 1.8.  Since it's a new feature that touches core
>>>> block layer code and several block drivers, I can't merge it into
>>>> 1.7-rc.
>>>
>>> Yay!  With these patches I can properly emulate WRITE SAME in the SCSI
>>> layer.
>>
>> Yes, you can, but only when write same is used to write zeroes. The other
>> case is still unhandled or needs emulation.
>
> WRITE SAME with UNMAP is incorrect in the current QEMU code.  Your patch
> let me fix it so that the payload can be read back with no change, *and*
> sectors are unmapped when possible.
>
> Paolo
>