Re: [Qemu-devel] [PATCH] ISCSI: Add support for thin-provisioning via discard/UNMAP and bigger LUNs

[Kevin Wolf]

Am 24.04.2012 08:46, schrieb Paolo Bonzini:
> Il 24/04/2012 08:29, Ronnie Sahlberg ha scritto:
>> Update the configure test for libiscsi support to detect version 1.3 or 
>> later.
>> Version 1.3 of libiscsi provides both READCAPACITY16 as well as UNMAP 
>> commands.
>>
>> Update the iscsi block layer to use READCAPACITY16 to detect the size of the 
>> LUN instead of READCAPACITY10. This allows support for LUNs larger than 2TB.
>>
>> Update to implement bdrv_aio_discard() using the UNMAP command.
>> This allows us to use thin-provisioned LUNs from TGTD and other iSCSI 
>> targets that support thin-provisioning.
> 
> Looks good.  Kevin, do you want me to take libiscsi patches via the SCSI
> tree?

Sure, if you like, go ahead. Feel free to update MAINTAINERS as well.

> As an aside, I am not really sure of the utility of adding these utility
> functions directly in libiscsi, rather than making it a pure transport
> library.  block/iscsi.c is going to grow as you add more functionality
> (e.g. WRITE SAME commands), and libiscsi will have to be updated each
> time in lockstep.
> 
> I can see the value of basic read/write/flush and readcap10/16, but with
> unmap it's starting to be a bit more specific.  Are there other clients
> of libiscsi that use these functions?  Should they be placed into
> block/iscsi.c or a new block/iscsi-cdb.c instead?

I think I agree. For the more obscure commands, the qemu driver should
probably build the CDB on its own and use a generic function.

Kevin