linux-kernel - RE: [PATCH 3/3] target/iblock: Add WRITE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <94D0CD8314A33A4D9D801C0FE68B40294CCF8D45@G9W0745.americas.hpqcorp.net>
Date:	Thu, 15 Nov 2012 20:01:27 +0000
From:	"Elliott, Robert (Server Storage)" <Elliott@...com>
To:	Christoph Hellwig <hch@....de>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
CC:	Christoph Hellwig <hch@...radead.org>,
	target-devel <target-devel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: RE: [PATCH 3/3] target/iblock: Add WRITE_SAME w/ UNMAP=0 emulation
	support

WRITE SAME always has a payload, regardless of the UNMAP bit value.

For WRITE SAME with UNMAP=0, it's extremely important; that's how what to write is specified.

For WRITE SAME with UNMAP=1, the device server is required to check that the payload matches the data that is returned for unmapped LBAs.  lf LBPRZ=1 (read zeros for unmapped LBAs), that means checking that the payload has all zeros.  In sbc3r33, this rule is tucked away in model section 4.7.3.4.3, not the command section 5.41.

I would like to change that rule (it's a nuisance and a performance burden), but that's the current rule going into SBC-3 letter ballot.  

Changing WRITE SAME with UNMAP=1 to ignore the payload would provide essentially the same functionality as changing the UNMAP command to be mandatory, not just a hint; both approaches have been discussed.



> -----Original Message-----
> From: linux-scsi-owner@...r.kernel.org [mailto:linux-scsi-
> owner@...r.kernel.org] On Behalf Of Christoph Hellwig
> Sent: Thursday, 15 November, 2012 1:33 PM
> To: Nicholas A. Bellinger
> Cc: Christoph Hellwig; target-devel; linux-scsi; linux-kernel; Christoph Hellwig;
> Martin K. Petersen
> Subject: Re: [PATCH 3/3] target/iblock: Add WRITE_SAME w/ UNMAP=0
> emulation support
> 
> On Thu, Nov 15, 2012 at 11:29:46AM -0800, Nicholas A. Bellinger wrote:
> > Well at least for the latter that is because UNMAP=0 does not have a
> > payload.  ;)
> 
> UNMAP=0 does have a payload, we just ignore it.  In fact I was told
> that targets should check for a completely zeroed sector sized payload
> for it if being pedantic.  I can't really find the justification for
> that in the standard - the closest thing to it is the stance about
> ignoring the unmap bit if the device is fully provisioned.
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/