[PATCH] scsi_debug 1.64 , remove detect(), "hotplug" hosts

[PATCH] scsi_debug 1.64 , remove detect(), "hotplug" hosts

[Douglas Gilbert]

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This patch is against lk 2.5.46-bk3 which includes
Christoph's work removing the requirement for
detect() functions in LLDDs. He sent me an example
for scsi_debug which I have built on with this patch.

As threatened, this version includes a "scsi_debug_add_host"
parameter. At kernel or module load time this is an absolute
number (0..127 are allowable and 1 is the default). So:
     modprobe scsi_debug scsi_debug_num_devs=20 scsi_debug_add_host=0
will result in no scsi_debug hosts (thus no devices) but
the driver has 20 slots available for devices.

Then a host can be introduced (simulated hotplug) by
     echo 1 > /sysfs/bus/scsi/drivers/scsi_debug/add_host
This causes a scsi_debug host to appear and devices get
found on it [14 in my system: 7 targets (0..6) each with
2 luns (0..1)]. Another host hotplug can be simulated by
     echo 1 > /sysfs/bus/scsi/drivers/scsi_debug/add_host
which results in another 6 devices being attached (for a
total of 20 scsi_debug devices as dictated by the original
scsi_debug_num_devs).

That last (second) scsi_debug host can be removed by
     echo -1 > /sysfs/bus/scsi/drivers/scsi_debug/add_host
and its 6 devices go. Another application of this "echo"
removes the first host and all remaining devices.

Seems to work fine.


Notes:
   - Christoph and Mike A. are pulling me in 2 different
     directions. In this case Christoph got to me first
     so I have moved along that direction. Mike's
     "/sysfs/bus/scsi_dbg_fake" has me perplexed ...
   - rmmod and subsequent modprobe's on scsi_debug
     sometimes blow up.
     Hopefully Patrick's fix (not in bk3?) addresses that.
   - this patch has a work around for a kernel sscanf() bug
     (parsing -ve numbers). Randy Dunlap has attended to that.
   - the simulated "hotplug" thread belongs to the echo command
     or some sysfs magic. scsi_debug could schedule a timer
     event and do the hotplug (hot unplug) in the context of
     a timer interrupt (?) for added reality.
   - cleaned out some extraneous includes and comments.
     Suggestions welcome.

Doug Gilbert


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Re: [PATCH] scsi_debug 1.64 , remove detect(), "hotplug" hosts

[Mike Anderson]

Douglas Gilbert [dougg@torque.net] wrote:
> Notes:
>   - Christoph and Mike A. are pulling me in 2 different
>     directions. In this case Christoph got to me first
>     so I have moved along that direction. Mike's
>     "/sysfs/bus/scsi_dbg_fake" has me perplexed ...

I was not trying to pull in another direction, but my patches may have
had to many steps in one chunk that may have made it look that way. 

I have split the functionality of my previous patch for scsi_debug into
smaller chunks. I believe there are advantages to scsi mid code and the
device model code in making scsi_debug look more like a real adapter.

I need to do more testing hopefully I can send you something Sunday if
you are interested.

>   - rmmod and subsequent modprobe's on scsi_debug
>     sometimes blow up.
>     Hopefully Patrick's fix (not in bk3?) addresses that.

I would use the changes that Patrick sent out as we had problems
with insmod / rmmod without these. I previously sent these to Mochel,
but he was in the process of moving and they probably will not show up
in a bk ( or fixes like these) until he can respond.

It seemed when I was re-working my patches that num_hosts_present is
used during scsi_debug_exit to cleanup, but is not incremented during
sdebug_add_host_write. There seems to a mixed use of scsi_debug_add_host
and num_hosts_present.

-andmike
--
Michael Anderson
andmike@us.ibm.com

Re: [PATCH] scsi_debug 1.64 , remove detect(), "hotplug" hosts

[Douglas Gilbert]

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Mike Anderson wrote:
> Douglas Gilbert [dougg@torque.net] wrote:
> 
<snip/>
> 
>>  - rmmod and subsequent modprobe's on scsi_debug
>>    sometimes blow up.
>>    Hopefully Patrick's fix (not in bk3?) addresses that.
> 
> 
> I would use the changes that Patrick sent out as we had problems
> with insmod / rmmod without these. I previously sent these to Mochel,
> but he was in the process of moving and they probably will not show up
> in a bk ( or fixes like these) until he can respond.
> 
> It seemed when I was re-working my patches that num_hosts_present is
> used during scsi_debug_exit to cleanup, but is not incremented during
> sdebug_add_host_write. There seems to a mixed use of scsi_debug_add_host
> and num_hosts_present.

Mike,
I have cleaned up that problem and a new version of
scsi_debug 1.64 is attached (applies against
2.5.46-bk3 (or the last version of 1.63 that I sent
a week ago)).
The second attachment is the changes to scsi_debug.c
since the start of this thread.

This version has been tested against a kernel with Patrick's
two patches for modprobe/rmmod stability that were sent to
this list last week. [One modifies sysfs source and the
other changes scsi_scan.c] In this environment I tried about
20 or more sequences of modprobe/rmmod on scsi_debug without
problems. Also using scsi_debug_add_host to add and remove
hosts caused no problems.

Doug Gilbert

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