Accessing static drive info w/o ATA identify and lockup with camcontrol identify

[Kevin Bowling]

This email is two parts that are somewhat related

#1 I have seen two cases where camcontrol identify can lock up a box.
On a system I have control over, I can downgrade the LSI firmware on a
machine with a SAS1008 and dispatch camcontrol identify to all the disks in
a loop.  I/O on the system will hang silently in the background fairly
quickly, but there is no indication as to how low the freeze is.  I'm not
sure if it's kernel side or firmware.  You wont initially notice it, but
then zfs will hang waiting for txgs and the machine is out to lunch.  On
this box, if I upgrade firmware I don't see the lockup.

I got another report where a user is seeing this on AHCI
https://github.com/saltstack/salt/issues/28518 with the same cause and
effect.  This user's lockup raises the spidy senses and makes me want to
dig deeper and make sure there isn't a loose end in kernel.

#2 This all came about because I want to poll device information like disk
model, serial number, speeds, etc.  Common use cases would be configuration
management systems and inventory databases.  Issuing an ATA identify seems
a bit much and could trigger unwanted HW errata like above.  I'm wondering
if it would be better to cache the data on interface change in sysctls or
something.  The data is static, read only, but we need to account for disk
swaps.

Regards,
Kevin