Re: Re: Re: BUG in kernel: Wrong Handling of USB HDD’s in scsiglue(slave_configure) and scsi/sd(sd_read_cache_type)

James Bottomley
2011-10-05T20:08:15Z

On Thu, 2011-10-06 at 01:21 +0530, Amit Sahrawat wrote:
> > The best we could probably offer is an interface to turn on the WCE bit
> > in software (technically, you can do this today
> > in /scsi/class/scsi_disk/<disk>/cache_type, it's just that it will try
> > to commit the change as a MODE_SELECT which will presumably fail).
> Thanks James, is this related with SCSI command MODE_SELECT? and this
> is to be passed when there is some failure?
> or simply doing an "echo <value>" to
> /scsi/class/scsi_disk/<disk>/cache_type? can you please elaborate a
> little

You tell me since you have the device. What that echo does is that it
does try to make the change permanent with a mode select ... that likely
won't work and the cache change only takes if the revalidated disk says
the write back has been enabled (which I really think it won't). So I
think you need an additional software bit to flip for the case where the
device lies.

James