Re: PATCH: usb-storage-set-last-sector-bug-flag.patch

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2008-01-24 at 09:21 -0800, Greg KH wrote:
> On Thu, Jan 24, 2008 at 06:07:00PM +0100, Stefan Richter wrote:
> > Greg KH wrote:
> > > I just am worried that we are
> > > now suddenly keeping access from the last sector for devices that
> > > currently did work just fine.
> > 
> > This new workaround doesn't prevent access to the last sector.  It only
> > breaks up a multi-sector access which would also reach the last sector
> > into several (two? I'm too lazy to look back in the mail thread)
> > accesses, in order to access the last sector in a dedicated
> > single-sector access.
> > 
> > So that's very differently to the fix-capacity workaround.  The
> > fix-capacity workaround manipulates the READ CAPACITY parameter data.
> > Therefore the fix-capacity workaround is unsafe for non-buggy devices.
> > 
> > The last-sector-(access-)bug workaround _only_ modifies the command
> > stream which is sent to the device.  A dangerous command is replaced by
> > equivalent safe commands.  These commands are luckily safe for _all_
> > devices, buggy and non-buggy ones.  The only cost of this workaround is
> > (1.) the code, (2.) the runtime/ bandwidth/ latency overhead for
> > accesses which reach the last sector.
> 
> Ok, thanks for explaining it better.  I have no objection to this change
> anymore.

So, for forms sake to take this through the SCSI tree I need at least
one USB person to ack it ...

James



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