Re: [PATCH] scsi: sd: stop SSD (non-rotational) disks before reboot

[Simon Arlott]

On 19/06/2020 00:31, Damien Le Moal wrote:
> On 2020/06/18 21:26, Simon Arlott wrote:
>> I haven't verified it, but the BIOS leaves the power off for several
>> seconds which should be long enough for the HDDs to spin down.
>> 
>> I'm less concerned about those suddenly losing power but it would be
>> nice to have a stop command sent to them too.
> 
> OK. So maybe the patch should be as simple as changing SYSTEM_RESTART state to
> SYSTEM_POWER_OFF if reboot=p is set, no ? Since that is consistent with the fact
> that reboot=p will cause power to go off, exactly the same as a regular
> shutdown, it seems cleaner and safer to use SYSTEM_POWER_OFF for the entire
> system, not just scsi disks.

That could be a bit misleading because the power isn't going to stay
off. Some of the network drivers have specific WOL behaviour changes
for a power off.

Power cycling the PSU is not something that every BIOS will do, so it's
not that simple. It could be a module parameter but I'd be concerned
that some other code will assuming the system should be powered off and
all of my reboots will become power off events.

-- 
Simon Arlott