Re: PATCH: exclude certain commands from emulated SCSI hosts

[Jens Axboe <axboe@suse.de>]

On Mon, Mar 24 2003, Linus Torvalds wrote:
> 
> On 24 Mar 2003, James Bottomley wrote:
> > > 
> > > For disk-like media:
> > > 
> > > READ_10
> > > WRITE_10
> > 
> > We do about the best we can for read and write.  For sd, we gauge the
> > size of the command from the size of the medium:  <1Gb=> six byte, from
> > 1Gb to 2Tb 10 byte, over 2Tb 16 byte, so I think this should all be
> > fine.
> 
> Really? The code was _supposed_ to always start off with READ/WRITE_10's,
> and then fall back to the old READ/WRITE_6 if it gets errors from that. Do 
> we really have some broken random-number generator semantic still in teh 
> SCSI layer? That sounds like a piece of crock.

It's not true, ->ten is set unconditionally and we only fall back to 6
byte cdb's if we see an ILLEGAL_REQUEST on a READ_10/WRITE_10.

So the logic is, always assume 10-byte commands. If an incoming request
cannot be addressed with 10-byte commands, use 16.

-- 
Jens Axboe