Re: [PATCH v11 4/9] Disallow changing the device state via sysfs into "deleted"

[James Bottomley <jbottomley@parallels.com>]

On Tue, 2013-06-25 at 10:41 +0200, Bart Van Assche wrote:
> On 06/24/13 19:59, James Bottomley wrote:
> > On Wed, 2013-06-12 at 14:53 +0200, Bart Van Assche wrote:
> >> Changing the state of a SCSI device via sysfs into "cancel" or
> >> "deleted" prevents removal of these devices by scsi_remove_host().
> >> Hence do not allow this. Also, introduce the symbolic name
> >> INVALID_SDEV_STATE, representing a value different from any valid
> >> SCSI device state. Update scsi_device_set_state() such that gcc
> >> does not issue a warning about an enumeration value not being
> >> handled inside a switch statement.
> >
> > zero is the invalid state, that's why the SDEV_ states start at 1.
> > Using a bare zero also means that gcc doesn't have to consider it in the
> > switch statement, so there's no need to introduce a new one.
> >
> > If we want to try to babysit user initiated state changes, then it looks
> > like OFFLINE<->RUNNING might be the only useful ones?
> 
> How about the BLOCKED<>RUNNING and QUIESCE<>RUNNING transitions ? I 
> think it may be useful for a user to trigger these as well.

They're part of paired state, so the user would tamper with assumptions
the HBA is making ... also, just changing the state doesn't help, the
queue needs to be restarted for these transitions which it currently
isn't.

James