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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