Re: scanning for LUNs
On 04/04/2013 07:12 PM, KY Srinivasan wrote:
-Original Message-
From: James Bottomley [mailto:jbottom...@parallels.com]
Sent: Thursday, April 04, 2013 11:15 AM
To: KY Srinivasan
Cc: gre...@linuxfoundation.org; linux-ker...@vger.kernel.org;
de...@linuxdriverproject.org; oher...@suse.com; h...@infradead.org; linux-
s...@vger.kernel.org
Subject: Re: scanning for LUNs
On Thu, 2013-04-04 at 08:12 -0700, K. Y. Srinivasan wrote:
Here is the code snippet for scanning LUNS (drivers/scsi/scsi_scan.c in
function
__scsi_scan_target()):
/*
* Scan LUN 0, if there is some response, scan further. Ideally, we
* would not configure LUN 0 until all LUNs are scanned.
*/
res = scsi_probe_and_add_lun(starget, 0, bflags, NULL, rescan,
NULL);
if (res == SCSI_SCAN_LUN_PRESENT || res ==
SCSI_SCAN_TARGET_PRESENT) {
if (scsi_report_lun_scan(starget, bflags, rescan) != 0)
So, if we don't get a response while scanning LUN0, we will not use
scsi_report_lun_scan().
On Hyper-V, the scsi emulation on the host does not treat LUN0 as
anything special and we
could have situations where the only device under a scsi controller is
at a location other than 0
or 1. In this case the standard LUN scanning code in Linux fails to
detect this device. Is this
behaviour expected? Why is LUN0 treated differently here. Looking at
the scsi spec, I am not sure
if this is what is specified. Any help/guidance will be greatly
appreciated.
Why don't you describe the problem. We can't scan randomly a bunch of
LUNs hoping for a response (the space is 10^19). SAM thinks you use
LUNW for this, but that's not well supported. We can't annoy USB
devices by probing with REPORT LUNS, so conventionally most arrays
return something for LUN0 even if they don't actually have one (That's
what the peripheral qualifier codes are supposed to be about). We
translate PQ1 and PQ2 to SCSI_SCAN_TARGET_PRESENT, which means no LUN,
but there is a target to scan here.
If you're sending back an error to an INQUIRY to LUN0, then you're out
of spec. The SCSI standards say:
SPC3 6.4.1: In response to an INQUIRY command received by an
incorrect logical unit, the SCSI target device shall return the
INQUIRY data with the peripheral qualifier set to the value
defined in 6.4.2. The INQUIRY command shall return CHECK
CONDITION status only when the device server is unable to return
the requested INQUIRY data
Thanks James. I will further investigate the issue on our platform.
Or check if you can use W_LUN for scanning.
I've done a patchset for this (check the mailing list).
Using W_LUN is precisely for this type of setup.
(And would provide me with another scenario for using W_LUNs :-)
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries Storage
h...@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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RE: scanning for LUNs
-Original Message-
From: Hannes Reinecke [mailto:h...@suse.de]
Sent: Monday, April 08, 2013 10:42 AM
To: KY Srinivasan
Cc: James Bottomley; gre...@linuxfoundation.org; linux-
ker...@vger.kernel.org; de...@linuxdriverproject.org; oher...@suse.com;
h...@infradead.org; linux-scsi@vger.kernel.org
Subject: Re: scanning for LUNs
On 04/04/2013 07:12 PM, KY Srinivasan wrote:
-Original Message-
From: James Bottomley [mailto:jbottom...@parallels.com]
Sent: Thursday, April 04, 2013 11:15 AM
To: KY Srinivasan
Cc: gre...@linuxfoundation.org; linux-ker...@vger.kernel.org;
de...@linuxdriverproject.org; oher...@suse.com; h...@infradead.org; linux-
s...@vger.kernel.org
Subject: Re: scanning for LUNs
On Thu, 2013-04-04 at 08:12 -0700, K. Y. Srinivasan wrote:
Here is the code snippet for scanning LUNS (drivers/scsi/scsi_scan.c in
function
__scsi_scan_target()):
/*
* Scan LUN 0, if there is some response, scan further. Ideally,
we
* would not configure LUN 0 until all LUNs are scanned.
*/
res = scsi_probe_and_add_lun(starget, 0, bflags, NULL, rescan,
NULL);
if (res == SCSI_SCAN_LUN_PRESENT || res ==
SCSI_SCAN_TARGET_PRESENT) {
if (scsi_report_lun_scan(starget, bflags, rescan) != 0)
So, if we don't get a response while scanning LUN0, we will not use
scsi_report_lun_scan().
On Hyper-V, the scsi emulation on the host does not treat LUN0 as
anything special and we
could have situations where the only device under a scsi controller is
at a location other than 0
or 1. In this case the standard LUN scanning code in Linux fails to
detect this device. Is this
behaviour expected? Why is LUN0 treated differently here. Looking at
the scsi spec, I am not sure
if this is what is specified. Any help/guidance will be greatly
appreciated.
Why don't you describe the problem. We can't scan randomly a bunch of
LUNs hoping for a response (the space is 10^19). SAM thinks you use
LUNW for this, but that's not well supported. We can't annoy USB
devices by probing with REPORT LUNS, so conventionally most arrays
return something for LUN0 even if they don't actually have one (That's
what the peripheral qualifier codes are supposed to be about). We
translate PQ1 and PQ2 to SCSI_SCAN_TARGET_PRESENT, which means no
LUN,
but there is a target to scan here.
If you're sending back an error to an INQUIRY to LUN0, then you're out
of spec. The SCSI standards say:
SPC3 6.4.1: In response to an INQUIRY command received by an
incorrect logical unit, the SCSI target device shall return the
INQUIRY data with the peripheral qualifier set to the value
defined in 6.4.2. The INQUIRY command shall return CHECK
CONDITION status only when the device server is unable to return
the requested INQUIRY data
Thanks James. I will further investigate the issue on our platform.
Or check if you can use W_LUN for scanning.
I've done a patchset for this (check the mailing list).
Using W_LUN is precisely for this type of setup.
(And would provide me with another scenario for using W_LUNs :-)
Thanks Hannes. What is the status on this patch; is it planned for the next
upstream release?
Regards,
K. Y
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries Storage
h...@suse.de+49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
--
To unsubscribe from this list: send the line unsubscribe linux-scsi in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: scanning for LUNs
On Thu, 2013-04-04 at 08:12 -0700, K. Y. Srinivasan wrote:
Here is the code snippet for scanning LUNS (drivers/scsi/scsi_scan.c in
function
__scsi_scan_target()):
/*
* Scan LUN 0, if there is some response, scan further. Ideally, we
* would not configure LUN 0 until all LUNs are scanned.
*/
res = scsi_probe_and_add_lun(starget, 0, bflags, NULL, rescan, NULL);
if (res == SCSI_SCAN_LUN_PRESENT || res == SCSI_SCAN_TARGET_PRESENT) {
if (scsi_report_lun_scan(starget, bflags, rescan) != 0)
So, if we don't get a response while scanning LUN0, we will not use
scsi_report_lun_scan().
On Hyper-V, the scsi emulation on the host does not treat LUN0 as
anything special and we
could have situations where the only device under a scsi controller is
at a location other than 0
or 1. In this case the standard LUN scanning code in Linux fails to
detect this device. Is this
behaviour expected? Why is LUN0 treated differently here. Looking at
the scsi spec, I am not sure
if this is what is specified. Any help/guidance will be greatly
appreciated.
Why don't you describe the problem. We can't scan randomly a bunch of
LUNs hoping for a response (the space is 10^19). SAM thinks you use
LUNW for this, but that's not well supported. We can't annoy USB
devices by probing with REPORT LUNS, so conventionally most arrays
return something for LUN0 even if they don't actually have one (That's
what the peripheral qualifier codes are supposed to be about). We
translate PQ1 and PQ2 to SCSI_SCAN_TARGET_PRESENT, which means no LUN,
but there is a target to scan here.
If you're sending back an error to an INQUIRY to LUN0, then you're out
of spec. The SCSI standards say:
SPC3 6.4.1: In response to an INQUIRY command received by an
incorrect logical unit, the SCSI target device shall return the
INQUIRY data with the peripheral qualifier set to the value
defined in 6.4.2. The INQUIRY command shall return CHECK
CONDITION status only when the device server is unable to return
the requested INQUIRY data
James
James
--
To unsubscribe from this list: send the line unsubscribe linux-scsi in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: scanning for LUNs
-Original Message-
From: James Bottomley [mailto:jbottom...@parallels.com]
Sent: Thursday, April 04, 2013 11:15 AM
To: KY Srinivasan
Cc: gre...@linuxfoundation.org; linux-ker...@vger.kernel.org;
de...@linuxdriverproject.org; oher...@suse.com; h...@infradead.org; linux-
s...@vger.kernel.org
Subject: Re: scanning for LUNs
On Thu, 2013-04-04 at 08:12 -0700, K. Y. Srinivasan wrote:
Here is the code snippet for scanning LUNS (drivers/scsi/scsi_scan.c in
function
__scsi_scan_target()):
/*
* Scan LUN 0, if there is some response, scan further. Ideally, we
* would not configure LUN 0 until all LUNs are scanned.
*/
res = scsi_probe_and_add_lun(starget, 0, bflags, NULL, rescan,
NULL);
if (res == SCSI_SCAN_LUN_PRESENT || res ==
SCSI_SCAN_TARGET_PRESENT) {
if (scsi_report_lun_scan(starget, bflags, rescan) != 0)
So, if we don't get a response while scanning LUN0, we will not use
scsi_report_lun_scan().
On Hyper-V, the scsi emulation on the host does not treat LUN0 as
anything special and we
could have situations where the only device under a scsi controller is
at a location other than 0
or 1. In this case the standard LUN scanning code in Linux fails to
detect this device. Is this
behaviour expected? Why is LUN0 treated differently here. Looking at
the scsi spec, I am not sure
if this is what is specified. Any help/guidance will be greatly
appreciated.
Why don't you describe the problem. We can't scan randomly a bunch of
LUNs hoping for a response (the space is 10^19). SAM thinks you use
LUNW for this, but that's not well supported. We can't annoy USB
devices by probing with REPORT LUNS, so conventionally most arrays
return something for LUN0 even if they don't actually have one (That's
what the peripheral qualifier codes are supposed to be about). We
translate PQ1 and PQ2 to SCSI_SCAN_TARGET_PRESENT, which means no LUN,
but there is a target to scan here.
If you're sending back an error to an INQUIRY to LUN0, then you're out
of spec. The SCSI standards say:
SPC3 6.4.1: In response to an INQUIRY command received by an
incorrect logical unit, the SCSI target device shall return the
INQUIRY data with the peripheral qualifier set to the value
defined in 6.4.2. The INQUIRY command shall return CHECK
CONDITION status only when the device server is unable to return
the requested INQUIRY data
Thanks James. I will further investigate the issue on our platform.
Regards,
K. Y
James
James
--
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the body of a message to majord...@vger.kernel.org
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