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

[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?

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?

Paolo