Re: [PATCH 1/3] tcm: Add Thin Provisioning / UNMAP emulation andBlock Limits VPD page

[Nicholas A. Bellinger]

On Tue, 2010-09-28 at 14:55 -0400, Martin K. Petersen wrote:
> >>>>> "nab" == Nicholas A Bellinger <nab@xxxxxxxxxxxxxxx> writes:
> 
> nab> This patch also adds the Block Limits VPD (0xb0) page
> 
> You should add the Thin Provisioning VPD page as well and set TPU and/or
> TPWS.
> 

Greetings mkp,

So I was looking at adding this VPD page orginally to set TPU=1 w/ DP=0
(because I don't believe there is currently way to get build the
PROVISIONING GROUP DESCRIPTORs from Block Discard knowledge), but I
ended getting a bit confused by the THRESHOLD EXPONENT, and what value
this should returned for the TCM/IBLOCK and TCM/FILEIO backstores when
blk_queue_discard()==1 is enabled.

Since this is currently not implemented in scsi_debug.c or used in any
way by sd.c AFAICT, do you have any additional information on how this
should be determined together with the UNMAP -> blk_issue_discard()
emulation bits..?

Thanks!

--nab

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