[stgt] [PATCH 12/15] ssc: add variable-length block read support

[FUJITA Tomonori]

On Wed, 26 Nov 2008 21:01:43 +1100
Mark Harvey <markh794 at gmail.com> wrote:

> FUJITA Tomonori wrote:
> > On Wed, 26 Nov 2008 17:46:38 +1100
> > "Mark Harvey" <markh794 at gmail.com> wrote:
> > 
> >>>> An attempt to read 128k from a 256k block results with an error message:
> >>>> # dd if=/dev/st1 bs=128k count=1 of=/tmp/block0
> >>>> dd: reading `/dev/st1': Cannot allocate memory
> >>>> 0+0 records in
> >>>> 0+0 records out
> >>>> 0 bytes (0 B) copied, 0.01287 seconds, 0.0 kB/s
> >>>>
> >>>> And /var/log/messages:
> >>>> kernel: st1: Failed to read 262144 byte block with 131072 byte transfer.
> >>> I think that this is a kernel message that st driver gives when the
> >>> INFORMATION field has a negative value. In this case, the INFORMATION
> >>> field had -128K.
> >>>
> >>> I've attached a new patch. The difference from the previous one is
> >>> just one line, it sets a negative value to the INFORMATION field when
> >>> the requested transfer length is smaller than the actual logical block
> >>> length.
> >>>
> >>>
> >>>> Disclaimer...
> >>>> I'm 99.99% positive, last time I tried this I received a different
> >>>> message and did in fact read 128k of data. This may be an
> >>>> implementation of dd used..
> >>> With the same tape drive?
> >> Yeah, same tape drive.
> >>
> >> I need to get hold of the 'other' linux box (Ubuntu x86_64bit I think)
> >> - where the above was from an SLES-10
> > 
> > I see. Please let me know if you see a different message.
> 
> OK, re-tested using Ubuntu - Same message as above - 'Can not allocate memory'..
> 
> Must be my faulty memory at play ;)

Thanks for testing. Good to know that the patch fixes the bugs
properly.

I'll merge this and release 0.9.2 (I've not merged many patches since
0.9.1 though).
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