- Subject: Re: PATCH: usb-storage-set-last-sector-bug-flag.patch
- From: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 25 Jan 2008 11:12:21 -0600
- Cc: USB development list <linux-usb-devel@xxxxxxxxxxxxxxxxxxxxx>, linux-scsi@xxxxxxxxxxxxxxx, USB Storage list <usb-storage@xxxxxxxxxxxxxxxxxxxxxxxx>, linux-usb@xxxxxxxxxxxxxxx, David Brown <usb-storage2@xxxxxxxxxx>, Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>, Hans de Goede <j.w.r.degoede@xxxxxx>, Boaz Harrosh <bharrosh@xxxxxxxxxxx>, Matthew Dharm <mdharm-scsi@xxxxxxxxxxxxxxxxxx>
- In-reply-to: <20080124172158.GC9665@xxxxxxxxx>
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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