Are you looking at section 5.7 on Reservations in
SPC-4 (spc4r23.pdf)? Table 51 seems to address your
question.
Complex commands like Persistent Reservation In and Out
often have a brief explanation under the command entry.
However in earlier chapters (in this case "Model common
to all device types" (section 5)) important mechanisms
such as reservations are explained in more detail.
Also Annex B discusses the mapping between the newer
Persistent Reservation commands and the now obsolete
Reserve/Release commands.
Doug Gilbert
lemons_terry@xxxxxxx wrote:
Hi
Thanks very much for the reply! The difference between those terms make
sense now.
I took a look at these comments in the code:
303 switch (pr_reg_type) {
304 case PR_TYPE_WRITE_EXCLUSIVE:
305 we = 1;
306 case PR_TYPE_EXCLUSIVE_ACCESS:
307 /*
308 * Some commands are only allowed for the persistent
reservation
309 * holder.
310 */
311 if (se_deve->deve_flags & DEF_PR_REGISTERED)
312 registered_nexus = 1;
313 break;
314 case PR_TYPE_WRITE_EXCLUSIVE_REGONLY:
315 we = 1;
316 case PR_TYPE_EXCLUSIVE_ACCESS_REGONLY:
317 /*
318 * Some commands are only allowed for registered I_T
Nexuses.
319 */
320 reg_only = 1;
321 if (se_deve->deve_flags & DEF_PR_REGISTERED)
322 registered_nexus = 1;
323 break;
324 case PR_TYPE_WRITE_EXCLUSIVE_ALLREG:
325 we = 1;
326 case PR_TYPE_EXCLUSIVE_ACCESS_ALLREG:
327 /*
328 * Each registered I_T Nexus is a reservation
holder.
329 */
330 all_reg = 1;
331 if (se_deve->deve_flags & DEF_PR_REGISTERED)
332 registered_nexus = 1;
333 break;
334 default:
335 return -1;
336 }
But I'm not able to devine the difference between 'write_exclusive' and
'write_exclusive_registrants_only'. Given that a registration must
exist before a reservation can be done, what is the difference between
these two? I just, again, looked for information describing these in
SPC-4, and didn't find any.
Thanks!
tl
-----Original Message-----
From: Nicholas A. Bellinger [mailto:nab@xxxxxxxxxxxxxxx]
Sent: Wednesday, April 07, 2010 2:48 PM
To: Lemons, Terry
Cc: linux-scsi@xxxxxxxxxxxxxxx
Subject: Re: SCSI persistent reservation terms
On Wed, 2010-04-07 at 10:55 -0400, lemons_terry@xxxxxxx wrote:
Hi
I'm trying to understand one aspect of the SCSI persistent reservation
functionality.
SPC-4 mentions the terms 'All Registrants' and 'Registrants Only', and
applies these
to both 'Write Exclusive' and 'Exclusive Access'. Nowhere can I find
a definition
of what these terms mean. If you would, please point me in the right
direction.
Greetings Terry,
'All Registrants' means that the persistent reservation holder is any
registstered I_T Nexus (eg: multiple reservation holders)
'Registrants Only' means that the persistent reservation holder is the
single registered I_T Nexus that has obtained the reservation via
RESERVE, PREEMPT, PREEMPT_AND_ABORT, or via another I_T Nexus with
REGISTER_AND_MOVE. (eg: single reservation holder)
You can find how this logic works for multi-fabric target mode by
grepping '_ALLREG' and '_REGONLY' in TCM code at:
http://git.kernel.org/?p=linux/kernel/git/nab/lio-core-2.6.git;a=blob;f=
drivers/target/target_core_pr.c
Best,
--nab
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