Re: [PATCH] sd: implement stop_on_shutdown

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> Darrick J. Wong wrote:
>> Tejun Heo wrote:
>>> sd doesn't stop (unload head) on shutdown.  This behavior is necessary
>>> for multi initiator cases.  Unloading head by powering off stresses
>>> the drive and sometimes produces distinct clunking noise which
>>> apparently disturbs users considering multiple reports on different
>>> distributions.  halt(8) usually puts the drives to sleep prior to
>>> shutdown but the implementation is fragile and it doesn't work with
>>> sleep-to-disk.
>> I wonder if this sort of thing (cache flush + spin down) is the sort of
>> thing that ought to be done to near-line storage at suspend time too,
>> though one would want allow_restart = 1 before doing such a thing.
> 
> For ATA, it's currently being done inside libata proper (a bit ugly).
> It would be nice to have those implemented at sd layer but I wonder how
> useful it's going to be for actual SCSI devices.  Do people actually
> suspend using SCSI?  If it's useful at the SCSI layer, I can implement
> and test it with SATA devices here.

There is always the open question for multi-initiator SCSI devices, as 
to who "owns" the SCSI device.  Some devices should be suspended/stopped 
when the machine is suspended/stopped, others not.

	Jeff