With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[Martin Petermann]

With kernel 2.6.19 a change was introduced that no sg device was 
generated if PQ=1, PDT=0x1f was returned from the particular device:

commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
Author: dave wysochanski <davidw@netapp.com>
Date:   Wed Aug 9 14:56:32 2006 -0400

     [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f

Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
port and to receive a generic device:

t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
total 0
-r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
-rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
-r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
-r--r--r-- 1 root root 4096 Aug  4 12:07 status
--w------- 1 root root 4096 Aug  4 12:07 uevent
--w------- 1 root root    0 Aug  4 13:46 unit_add
--w------- 1 root root    0 Aug  5 14:24 unit_remove
t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
unit_add
t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
total 0
drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
-r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
-rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
-r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
-r--r--r-- 1 root root 4096 Aug  4 12:07 status
--w------- 1 root root 4096 Aug  4 12:07 uevent
--w------- 1 root root    0 Aug  5 14:25 unit_add
--w------- 1 root root    0 Aug  5 14:24 unit_remove
t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
[0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0

After this fix there is no /dev/sg0 device generated.

We are utilizing the possibility to create such a device for the 
sg_utils commands in the case no other LUN has been attached to a port.

I do not want to put this fix into question. I would like to know if 
someone has an idea how to workaround this problem and to generate a 
generic device in user space using kernel 2.6.19 or a later version.

Regards
    Martin

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[James Bottomley]

On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
> With kernel 2.6.19 a change was introduced that no sg device was 
> generated if PQ=1, PDT=0x1f was returned from the particular device:
> 
> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
> Author: dave wysochanski <davidw@netapp.com>
> Date:   Wed Aug 9 14:56:32 2006 -0400
> 
>      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
> 
> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
> port and to receive a generic device:
> 
> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> total 0
> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> --w------- 1 root root 4096 Aug  4 12:07 uevent
> --w------- 1 root root    0 Aug  4 13:46 unit_add
> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
> unit_add
> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> total 0
> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> --w------- 1 root root 4096 Aug  4 12:07 uevent
> --w------- 1 root root    0 Aug  5 14:25 unit_add
> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
> 
> After this fix there is no /dev/sg0 device generated.
> 
> We are utilizing the possibility to create such a device for the 
> sg_utils commands in the case no other LUN has been attached to a port.
> 
> I do not want to put this fix into question. I would like to know if 
> someone has an idea how to workaround this problem and to generate a 
> generic device in user space using kernel 2.6.19 or a later version.

First of all, why is the device returning PQ=1 PTD=0x1f? this should
mean its not connected and probably doesn't exist... ie inaccessible
without some unspecified action being taken.  If you can use it, it's
clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
be for something in s390 to fix up the inquiry data ... or we could
allow you could have a script to force it to appear (as in if you send a
specific scan for this one LUN we could override the catch in the code
that throws it out again).

James

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[Swen Schillig]

On Tuesday 05 August 2008 18:51, James Bottomley wrote:
> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
> > With kernel 2.6.19 a change was introduced that no sg device was 
> > generated if PQ=1, PDT=0x1f was returned from the particular device:
> > 
> > commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
> > Author: dave wysochanski <davidw@netapp.com>
> > Date:   Wed Aug 9 14:56:32 2006 -0400
> > 
> >      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
> > 
> > Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
> > port and to receive a generic device:
> > 
> > t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > total 0
> > -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > --w------- 1 root root 4096 Aug  4 12:07 uevent
> > --w------- 1 root root    0 Aug  4 13:46 unit_add
> > --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
> > unit_add
> > t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > total 0
> > drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
> > -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > --w------- 1 root root 4096 Aug  4 12:07 uevent
> > --w------- 1 root root    0 Aug  5 14:25 unit_add
> > --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
> > [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
> > 
> > After this fix there is no /dev/sg0 device generated.
> > 
> > We are utilizing the possibility to create such a device for the 
> > sg_utils commands in the case no other LUN has been attached to a port.
> > 
> > I do not want to put this fix into question. I would like to know if 
> > someone has an idea how to workaround this problem and to generate a 
> > generic device in user space using kernel 2.6.19 or a later version.
> 
> First of all, why is the device returning PQ=1 PTD=0x1f? this should
> mean its not connected and probably doesn't exist... ie inaccessible
> without some unspecified action being taken.  If you can use it, it's
> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
> be for something in s390 to fix up the inquiry data ... or we could
> allow you could have a script to force it to appear (as in if you send a
> specific scan for this one LUN we could override the catch in the code
> that throws it out again).
> 
> James
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

James

I think Martin is saying that this LUN is a non existent one which is just used for scanning
all available (existing) LUNs on the remote storage port.
That's why PQ=1 PTD=0x1f are returned and correct !

So what's required here is the possibility to add a "dummy" LUN which can be used just for this purpose.
Not sure whether this is covered by anything in the standard

Cheers Swen

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[Douglas Gilbert]

Swen Schillig wrote:
> On Tuesday 05 August 2008 18:51, James Bottomley wrote:
>> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
>>> With kernel 2.6.19 a change was introduced that no sg device was 
>>> generated if PQ=1, PDT=0x1f was returned from the particular device:
>>>
>>> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
>>> Author: dave wysochanski <davidw@netapp.com>
>>> Date:   Wed Aug 9 14:56:32 2006 -0400
>>>
>>>      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
>>>
>>> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
>>> port and to receive a generic device:
>>>
>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
>>> total 0
>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
>>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
>>> --w------- 1 root root 4096 Aug  4 12:07 uevent
>>> --w------- 1 root root    0 Aug  4 13:46 unit_add
>>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
>>> unit_add
>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
>>> total 0
>>> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
>>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
>>> --w------- 1 root root 4096 Aug  4 12:07 uevent
>>> --w------- 1 root root    0 Aug  5 14:25 unit_add
>>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
>>> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
>>>
>>> After this fix there is no /dev/sg0 device generated.
>>>
>>> We are utilizing the possibility to create such a device for the 
>>> sg_utils commands in the case no other LUN has been attached to a port.
>>>
>>> I do not want to put this fix into question. I would like to know if 
>>> someone has an idea how to workaround this problem and to generate a 
>>> generic device in user space using kernel 2.6.19 or a later version.
>> First of all, why is the device returning PQ=1 PTD=0x1f? this should
>> mean its not connected and probably doesn't exist... ie inaccessible
>> without some unspecified action being taken.  If you can use it, it's
>> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
>> be for something in s390 to fix up the inquiry data ... or we could
>> allow you could have a script to force it to appear (as in if you send a
>> specific scan for this one LUN we could override the catch in the code
>> that throws it out again).
>>
>> James
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
> 
> James
> 
> I think Martin is saying that this LUN is a non existent one which is just used for scanning
> all available (existing) LUNs on the remote storage port.
> That's why PQ=1 PTD=0x1f are returned and correct !
> 
> So what's required here is the possibility to add a "dummy" LUN which can be used just for this purpose.
> Not sure whether this is covered by anything in the standard

That sounds like a job for the REPORT LUNS well known logical
unit (WLUN or W-LUN). I implemented one in the scsi_debug driver.
See the description of the "no_lun_0" parameter in
http://sg.torque.net/sg/sdebug26.html

You might try:
   echo "- - 49409" > /sys/class/scsi_host/host<n>/scan
where "host<n>" is the controller in question. Then
see if a WLUN has appeared as a sg device node.

Doug Gilbert

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[James Bottomley]

On Wed, 2008-08-06 at 11:06 +0200, Douglas Gilbert wrote:
> Swen Schillig wrote:
> > On Tuesday 05 August 2008 18:51, James Bottomley wrote:
> >> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
> >>> With kernel 2.6.19 a change was introduced that no sg device was 
> >>> generated if PQ=1, PDT=0x1f was returned from the particular device:
> >>>
> >>> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
> >>> Author: dave wysochanski <davidw@netapp.com>
> >>> Date:   Wed Aug 9 14:56:32 2006 -0400
> >>>
> >>>      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
> >>>
> >>> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
> >>> port and to receive a generic device:
> >>>
> >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> >>> total 0
> >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> >>> --w------- 1 root root    0 Aug  4 13:46 unit_add
> >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
> >>> unit_add
> >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> >>> total 0
> >>> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
> >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> >>> --w------- 1 root root    0 Aug  5 14:25 unit_add
> >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
> >>> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
> >>>
> >>> After this fix there is no /dev/sg0 device generated.
> >>>
> >>> We are utilizing the possibility to create such a device for the 
> >>> sg_utils commands in the case no other LUN has been attached to a port.
> >>>
> >>> I do not want to put this fix into question. I would like to know if 
> >>> someone has an idea how to workaround this problem and to generate a 
> >>> generic device in user space using kernel 2.6.19 or a later version.
> >> First of all, why is the device returning PQ=1 PTD=0x1f? this should
> >> mean its not connected and probably doesn't exist... ie inaccessible
> >> without some unspecified action being taken.  If you can use it, it's
> >> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
> >> be for something in s390 to fix up the inquiry data ... or we could
> >> allow you could have a script to force it to appear (as in if you send a
> >> specific scan for this one LUN we could override the catch in the code
> >> that throws it out again).
> >>
> >> James
> >>
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>
> > 
> > James
> > 
> > I think Martin is saying that this LUN is a non existent one which is just used for scanning
> > all available (existing) LUNs on the remote storage port.
> > That's why PQ=1 PTD=0x1f are returned and correct !
> > 
> > So what's required here is the possibility to add a "dummy" LUN which can be used just for this purpose.
> > Not sure whether this is covered by anything in the standard
> 
> That sounds like a job for the REPORT LUNS well known logical
> unit (WLUN or W-LUN). I implemented one in the scsi_debug driver.
> See the description of the "no_lun_0" parameter in
> http://sg.torque.net/sg/sdebug26.html
> 
> You might try:
>    echo "- - 49409" > /sys/class/scsi_host/host<n>/scan
> where "host<n>" is the controller in question. Then
> see if a WLUN has appeared as a sg device node.

Actually, if this thing is WLUN or ZLUN ... that's something we should
support unconditionally without looking at the PQ bit ... is that how it
is supposed to show up on the Z?

James

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[Martin Petermann]

Douglas Gilbert wrote:
> Swen Schillig wrote:
>> On Tuesday 05 August 2008 18:51, James Bottomley wrote:
>>> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
>>>> With kernel 2.6.19 a change was introduced that no sg device was 
>>>> generated if PQ=1, PDT=0x1f was returned from the particular device:
>>>>
>>>> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
>>>> Author: dave wysochanski <davidw@netapp.com>
>>>> Date:   Wed Aug 9 14:56:32 2006 -0400
>>>>
>>>>      [SCSI] Don't add scsi_device for devices that return PQ=1, 
>>>> PDT=0x1f
>>>>
>>>> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to 
>>>> a port and to receive a generic device:
>>>>
>>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
>>>> total 0
>>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
>>>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
>>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
>>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
>>>> --w------- 1 root root 4096 Aug  4 12:07 uevent
>>>> --w------- 1 root root    0 Aug  4 13:46 unit_add
>>>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
>>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
>>>> unit_add
>>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
>>>> total 0
>>>> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
>>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
>>>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
>>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
>>>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
>>>> --w------- 1 root root 4096 Aug  4 12:07 uevent
>>>> --w------- 1 root root    0 Aug  5 14:25 unit_add
>>>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
>>>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
>>>> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
>>>>
>>>> After this fix there is no /dev/sg0 device generated.
>>>>
>>>> We are utilizing the possibility to create such a device for the 
>>>> sg_utils commands in the case no other LUN has been attached to a port.
>>>>
>>>> I do not want to put this fix into question. I would like to know if 
>>>> someone has an idea how to workaround this problem and to generate a 
>>>> generic device in user space using kernel 2.6.19 or a later version.
>>> First of all, why is the device returning PQ=1 PTD=0x1f? this should
>>> mean its not connected and probably doesn't exist... ie inaccessible
>>> without some unspecified action being taken.  If you can use it, it's
>>> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
>>> be for something in s390 to fix up the inquiry data ... or we could
>>> allow you could have a script to force it to appear (as in if you send a
>>> specific scan for this one LUN we could override the catch in the code
>>> that throws it out again).
>>>
>>> James
>>>
>>>
>>> -- 
>>> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>> James
>>
>> I think Martin is saying that this LUN is a non existent one which is 
>> just used for scanning
>> all available (existing) LUNs on the remote storage port.
>> That's why PQ=1 PTD=0x1f are returned and correct !
>>
>> So what's required here is the possibility to add a "dummy" LUN which 
>> can be used just for this purpose.
>> Not sure whether this is covered by anything in the standard
> 
> That sounds like a job for the REPORT LUNS well known logical
> unit (WLUN or W-LUN). I implemented one in the scsi_debug driver.
> See the description of the "no_lun_0" parameter in
> http://sg.torque.net/sg/sdebug26.html
> 
> You might 
>   echo "- - 49409" > /sys/class/scsi_host/host<n>/scan
> where "host<n>" is the controller in question. Then
> see if a WLUN has appeared as a sg device node.
> 
> Doug Gilbert
> 
> 
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

I'm not so familiar with SCSI on x86 Linux: the command you propose 
seems to initiate a scan on the specific host/port or the LUN. This is 
not implemented on s390 Linux. The reason for this difference probably 
(I need to speculate here since I'm quite new here) are related that on 
s390 different virtual machines share the same FC adapter and and a 
automatically detection and attachment of LUNs is not desired: different 
VMs can see the same LUNs if they share the same adapter. If I run the 
'echo "- - 49409" > /sys/class/scsi_host/host<n>/scan' command on x86 
Linux LUNs are automatically attached. On s390 Linux a manually 
attachment has been implemented by writing the LUN number to

/sys/bus/ccw/devices/<adapter ID>/<port ID>/unit_add

To find out the LUNs available to a specific port it should be 
sufficient to run the REPORT_LUNS SCSI command to any of the available 
generic devices of the port of interest. If there is no LUN added so far 
  the idea was to add a LUN 0 and run this command to it's generic 
device.    Because of the fix in the Linux kernel this is not possible 
anymore.


Regards
    Martin

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[Swen Schillig]

On Wednesday 06 August 2008 18:58, James Bottomley wrote:
> On Wed, 2008-08-06 at 11:06 +0200, Douglas Gilbert wrote:
> > Swen Schillig wrote:
> > > On Tuesday 05 August 2008 18:51, James Bottomley wrote:
> > >> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
> > >>> With kernel 2.6.19 a change was introduced that no sg device was 
> > >>> generated if PQ=1, PDT=0x1f was returned from the particular device:
> > >>>
> > >>> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
> > >>> Author: dave wysochanski <davidw@netapp.com>
> > >>> Date:   Wed Aug 9 14:56:32 2006 -0400
> > >>>
> > >>>      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
> > >>>
> > >>> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
> > >>> port and to receive a generic device:
> > >>>
> > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > >>> total 0
> > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> > >>> --w------- 1 root root    0 Aug  4 13:46 unit_add
> > >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
> > >>> unit_add
> > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > >>> total 0
> > >>> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
> > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> > >>> --w------- 1 root root    0 Aug  5 14:25 unit_add
> > >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
> > >>> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
> > >>>
> > >>> After this fix there is no /dev/sg0 device generated.
> > >>>
> > >>> We are utilizing the possibility to create such a device for the 
> > >>> sg_utils commands in the case no other LUN has been attached to a port.
> > >>>
> > >>> I do not want to put this fix into question. I would like to know if 
> > >>> someone has an idea how to workaround this problem and to generate a 
> > >>> generic device in user space using kernel 2.6.19 or a later version.
> > >> First of all, why is the device returning PQ=1 PTD=0x1f? this should
> > >> mean its not connected and probably doesn't exist... ie inaccessible
> > >> without some unspecified action being taken.  If you can use it, it's
> > >> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
> > >> be for something in s390 to fix up the inquiry data ... or we could
> > >> allow you could have a script to force it to appear (as in if you send a
> > >> specific scan for this one LUN we could override the catch in the code
> > >> that throws it out again).
> > >>
> > >> James
> > >>
> > >>
> > >> --
> > >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> > >> the body of a message to majordomo@vger.kernel.org
> > >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > >>
> > > 
> > > James
> > > 
> > > I think Martin is saying that this LUN is a non existent one which is just used for scanning
> > > all available (existing) LUNs on the remote storage port.
> > > That's why PQ=1 PTD=0x1f are returned and correct !
> > > 
> > > So what's required here is the possibility to add a "dummy" LUN which can be used just for this purpose.
> > > Not sure whether this is covered by anything in the standard
> > 
> > That sounds like a job for the REPORT LUNS well known logical
> > unit (WLUN or W-LUN). I implemented one in the scsi_debug driver.
> > See the description of the "no_lun_0" parameter in
> > http://sg.torque.net/sg/sdebug26.html
> > 
> > You might try:
> >    echo "- - 49409" > /sys/class/scsi_host/host<n>/scan
> > where "host<n>" is the controller in question. Then
> > see if a WLUN has appeared as a sg device node.
> 
> Actually, if this thing is WLUN or ZLUN ... that's something we should
> support unconditionally without looking at the PQ bit ... is that how it
> is supposed to show up on the Z?
> 
> James
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
Yes, that's exactly how it should be !
That would mean in our case that LUN 0xc101 would get a generic device 
which could be used for scanning.

so something like 

Index: HEAD/drivers/scsi/scsi_scan.c
===================================================================
--- HEAD.orig/drivers/scsi/scsi_scan.c
+++ HEAD/drivers/scsi/scsi_scan.c
@@ -1080,7 +1080,7 @@ static int scsi_probe_and_add_lun(struct
         * PDT=1Fh none (no FDD connected to the requested logical unit)
         */
        if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) &&
-            (result[0] & 0x1f) == 0x1f) {
+            (result[0] & 0x1f) == 0x1f && (lun & 0xc100) != 0xc100)) {
                SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
                                        "scsi scan: peripheral device type"
                                        " of 31, no device added\n"));

could do the trick ( or maybe something fancier).

Cheers Swen
--
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the body of a message to majordomo@vger.kernel.org
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Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[James Bottomley]

On Fri, 2008-08-08 at 08:52 +0200, Swen Schillig wrote:
> On Wednesday 06 August 2008 18:58, James Bottomley wrote:
> > On Wed, 2008-08-06 at 11:06 +0200, Douglas Gilbert wrote:
> > > Swen Schillig wrote:
> > > > On Tuesday 05 August 2008 18:51, James Bottomley wrote:
> > > >> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
> > > >>> With kernel 2.6.19 a change was introduced that no sg device was 
> > > >>> generated if PQ=1, PDT=0x1f was returned from the particular device:
> > > >>>
> > > >>> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
> > > >>> Author: dave wysochanski <davidw@netapp.com>
> > > >>> Date:   Wed Aug 9 14:56:32 2006 -0400
> > > >>>
> > > >>>      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
> > > >>>
> > > >>> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
> > > >>> port and to receive a generic device:
> > > >>>
> > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > > >>> total 0
> > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > > >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > > >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> > > >>> --w------- 1 root root    0 Aug  4 13:46 unit_add
> > > >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
> > > >>> unit_add
> > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > > >>> total 0
> > > >>> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
> > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > > >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > > >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> > > >>> --w------- 1 root root    0 Aug  5 14:25 unit_add
> > > >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
> > > >>> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
> > > >>>
> > > >>> After this fix there is no /dev/sg0 device generated.
> > > >>>
> > > >>> We are utilizing the possibility to create such a device for the 
> > > >>> sg_utils commands in the case no other LUN has been attached to a port.
> > > >>>
> > > >>> I do not want to put this fix into question. I would like to know if 
> > > >>> someone has an idea how to workaround this problem and to generate a 
> > > >>> generic device in user space using kernel 2.6.19 or a later version.
> > > >> First of all, why is the device returning PQ=1 PTD=0x1f? this should
> > > >> mean its not connected and probably doesn't exist... ie inaccessible
> > > >> without some unspecified action being taken.  If you can use it, it's
> > > >> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
> > > >> be for something in s390 to fix up the inquiry data ... or we could
> > > >> allow you could have a script to force it to appear (as in if you send a
> > > >> specific scan for this one LUN we could override the catch in the code
> > > >> that throws it out again).
> > > >>
> > > >> James
> > > >>
> > > >>
> > > >> --
> > > >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> > > >> the body of a message to majordomo@vger.kernel.org
> > > >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > >>
> > > > 
> > > > James
> > > > 
> > > > I think Martin is saying that this LUN is a non existent one which is just used for scanning
> > > > all available (existing) LUNs on the remote storage port.
> > > > That's why PQ=1 PTD=0x1f are returned and correct !
> > > > 
> > > > So what's required here is the possibility to add a "dummy" LUN which can be used just for this purpose.
> > > > Not sure whether this is covered by anything in the standard
> > > 
> > > That sounds like a job for the REPORT LUNS well known logical
> > > unit (WLUN or W-LUN). I implemented one in the scsi_debug driver.
> > > See the description of the "no_lun_0" parameter in
> > > http://sg.torque.net/sg/sdebug26.html
> > > 
> > > You might try:
> > >    echo "- - 49409" > /sys/class/scsi_host/host<n>/scan
> > > where "host<n>" is the controller in question. Then
> > > see if a WLUN has appeared as a sg device node.
> > 
> > Actually, if this thing is WLUN or ZLUN ... that's something we should
> > support unconditionally without looking at the PQ bit ... is that how it
> > is supposed to show up on the Z?
> > 
> > James
> > 
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> Yes, that's exactly how it should be !
> That would mean in our case that LUN 0xc101 would get a generic device 
> which could be used for scanning.
> 
> so something like 
> 
> Index: HEAD/drivers/scsi/scsi_scan.c
> ===================================================================
> --- HEAD.orig/drivers/scsi/scsi_scan.c
> +++ HEAD/drivers/scsi/scsi_scan.c
> @@ -1080,7 +1080,7 @@ static int scsi_probe_and_add_lun(struct
>          * PDT=1Fh none (no FDD connected to the requested logical unit)
>          */
>         if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) &&
> -            (result[0] & 0x1f) == 0x1f) {
> +            (result[0] & 0x1f) == 0x1f && (lun & 0xc100) != 0xc100)) {
>                 SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
>                                         "scsi scan: peripheral device type"
>                                         " of 31, no device added\n"));

I think you mean lun & 0xff00 == 0xc100

perhaps there should be #defines for this too, something like

#define SCSI_W_LUN_BASE 0x1c00
#define SCSI_W_LUN_REPORT_LUNS (SCSI_W_LUN_BASE + 1)
#define SCSI_W_LUN_ACCESS_CONTROL (SCSI_W_LUN_BASE + 2)
#define SCSI_W_LUN_TARGET_LOG_PAGE (SCSI_W_LUN_BASE + 3)

James

Re: With kernel 2.6.19 no sg devices for devices that return PQ=1, PDT=0x1f

[Swen Schillig]

On Saturday 09 August 2008 18:50, James Bottomley wrote:
> On Fri, 2008-08-08 at 08:52 +0200, Swen Schillig wrote:
> > On Wednesday 06 August 2008 18:58, James Bottomley wrote:
> > > On Wed, 2008-08-06 at 11:06 +0200, Douglas Gilbert wrote:
> > > > Swen Schillig wrote:
> > > > > On Tuesday 05 August 2008 18:51, James Bottomley wrote:
> > > > >> On Tue, 2008-08-05 at 14:40 +0200, Martin Petermann wrote:
> > > > >>> With kernel 2.6.19 a change was introduced that no sg device was 
> > > > >>> generated if PQ=1, PDT=0x1f was returned from the particular device:
> > > > >>>
> > > > >>> commit 84961f28e9d13a4b193d0c8545f3c060c1890ff3
> > > > >>> Author: dave wysochanski <davidw@netapp.com>
> > > > >>> Date:   Wed Aug 9 14:56:32 2006 -0400
> > > > >>>
> > > > >>>      [SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f
> > > > >>>
> > > > >>> Before it was possible on Linux 390 in user space to a e.g. LUN 0 to a 
> > > > >>> port and to receive a generic device:
> > > > >>>
> > > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > > > >>> total 0
> > > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > > > >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > > > >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> > > > >>> --w------- 1 root root    0 Aug  4 13:46 unit_add
> > > > >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # echo 0 > 
> > > > >>> unit_add
> > > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # ll
> > > > >>> total 0
> > > > >>> drwxr-xr-x 2 root root    0 Aug  5 14:25 0x0000000000000000
> > > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 access_denied
> > > > >>> -rw-r--r-- 1 root root 4096 Aug  4 12:07 failed
> > > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 in_recovery
> > > > >>> -r--r--r-- 1 root root 4096 Aug  4 12:07 status
> > > > >>> --w------- 1 root root 4096 Aug  4 12:07 uevent
> > > > >>> --w------- 1 root root    0 Aug  5 14:25 unit_add
> > > > >>> --w------- 1 root root    0 Aug  5 14:24 unit_remove
> > > > >>> t6345056:/sys/bus/ccw/devices/0.0.5922/0x500507630313c562 # lsscsi -g
> > > > >>> [0:0:0:0]    no dev  IBM      2107900          2.27  -         /dev/sg0
> > > > >>>
> > > > >>> After this fix there is no /dev/sg0 device generated.
> > > > >>>
> > > > >>> We are utilizing the possibility to create such a device for the 
> > > > >>> sg_utils commands in the case no other LUN has been attached to a port.
> > > > >>>
> > > > >>> I do not want to put this fix into question. I would like to know if 
> > > > >>> someone has an idea how to workaround this problem and to generate a 
> > > > >>> generic device in user space using kernel 2.6.19 or a later version.
> > > > >> First of all, why is the device returning PQ=1 PTD=0x1f? this should
> > > > >> mean its not connected and probably doesn't exist... ie inaccessible
> > > > >> without some unspecified action being taken.  If you can use it, it's
> > > > >> clearly not behaving like a PQ=1 LUN.  Perhaps the simplest thing would
> > > > >> be for something in s390 to fix up the inquiry data ... or we could
> > > > >> allow you could have a script to force it to appear (as in if you send a
> > > > >> specific scan for this one LUN we could override the catch in the code
> > > > >> that throws it out again).
> > > > >>
> > > > >> James
> > > > >>
> > > > >>
> > > > >> --
> > > > >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> > > > >> the body of a message to majordomo@vger.kernel.org
> > > > >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > > >>
> > > > > 
> > > > > James
> > > > > 
> > > > > I think Martin is saying that this LUN is a non existent one which is just used for scanning
> > > > > all available (existing) LUNs on the remote storage port.
> > > > > That's why PQ=1 PTD=0x1f are returned and correct !
> > > > > 
> > > > > So what's required here is the possibility to add a "dummy" LUN which can be used just for this purpose.
> > > > > Not sure whether this is covered by anything in the standard
> > > > 
> > > > That sounds like a job for the REPORT LUNS well known logical
> > > > unit (WLUN or W-LUN). I implemented one in the scsi_debug driver.
> > > > See the description of the "no_lun_0" parameter in
> > > > http://sg.torque.net/sg/sdebug26.html
> > > > 
> > > > You might try:
> > > >    echo "- - 49409" > /sys/class/scsi_host/host<n>/scan
> > > > where "host<n>" is the controller in question. Then
> > > > see if a WLUN has appeared as a sg device node.
> > > 
> > > Actually, if this thing is WLUN or ZLUN ... that's something we should
> > > support unconditionally without looking at the PQ bit ... is that how it
> > > is supposed to show up on the Z?
> > > 
> > > James
> > > 
> > > 
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > 
> > Yes, that's exactly how it should be !
> > That would mean in our case that LUN 0xc101 would get a generic device 
> > which could be used for scanning.
> > 
> > so something like 
> > 
> > Index: HEAD/drivers/scsi/scsi_scan.c
> > ===================================================================
> > --- HEAD.orig/drivers/scsi/scsi_scan.c
> > +++ HEAD/drivers/scsi/scsi_scan.c
> > @@ -1080,7 +1080,7 @@ static int scsi_probe_and_add_lun(struct
> >          * PDT=1Fh none (no FDD connected to the requested logical unit)
> >          */
> >         if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) &&
> > -            (result[0] & 0x1f) == 0x1f) {
> > +            (result[0] & 0x1f) == 0x1f && (lun & 0xc100) != 0xc100)) {
> >                 SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO
> >                                         "scsi scan: peripheral device type"
> >                                         " of 31, no device added\n"));
> 
> I think you mean lun & 0xff00 == 0xc100
> 
> perhaps there should be #defines for this too, something like
> 
> #define SCSI_W_LUN_BASE 0x1c00
> #define SCSI_W_LUN_REPORT_LUNS (SCSI_W_LUN_BASE + 1)
> #define SCSI_W_LUN_ACCESS_CONTROL (SCSI_W_LUN_BASE + 2)
> #define SCSI_W_LUN_TARGET_LOG_PAGE (SCSI_W_LUN_BASE + 3)
> 
> James
> 
Yes, sorry that's what I meant actually, ok despite the "==" which should be "!=" like in Martins patch.
But I'm not sure what you need the defines for, they're not used anywhere, are they ?

Cheers Swen