Re: [Bug 12207] block reads/writes > 122880 bytes to USB tape drive gives EBUSY

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

On Tue, 2008-12-23 at 18:30 +0200, Kai Makisara wrote:
> On Tue, 23 Dec 2008, bugme-daemon@bugzilla.kernel.org wrote:
> 
> > http://bugzilla.kernel.org/show_bug.cgi?id=12207
> > 
> > 
> > 
> > 
> > 
> > ------- Comment #13 from alan@lxorguk.ukuu.org.uk  2008-12-23 08:18 -------
> > What may have happened is something else changed to trigger the enforcement of
> > that limit on not block paths ?
> > 
> Something like this ;-) From 2.6.16 st.c has used scsi_execute_async() 
> that sends the request to the block layer.

That's probably it!  Realistically, though, allowing st to override the
block limits was wrong.  Most drivers (except USB) don't set these
arbitrarily, they usually represent fundamental hardware limits.  If you
force down a transaction that's larger than they declared themselves
capable of, they'll do strange things like wrap descriptors or truncate
the transaction, which will cause silent data corruption.

Hopefully we can figure out how to get USB working.

James