[Bug 16058] [BUG] Cannot boot any kernel from 2.6.27 on if a 256 byte sector SCSI disk is attached

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https://bugzilla.kernel.org/show_bug.cgi?id=16058





--- Comment #6 from Anonymous Emailer <anonymous@kernel-bugs.osdl.org>  2010-05-28 16:34:28 ---
Reply-To: James.Bottomley@suse.de

On Fri, 2010-05-28 at 10:58 -0400, Alan Stern wrote:
> On Fri, 28 May 2010, Mark Hounschell wrote:
> 
> > First READ(10):
> > 
> >  sde:
> > ahc_calc_residual: Entered
> > ahc_calc_residual: return Case 5-1 resid = 0x800
> > ahc_calc_residual: return Case 5-2 resid = 0x800
> > 
> > scsi_finish_command: Entered for cmd(10):0x28 0x00 0x00 0x00 0x00 0x00
> > 0x00 0x00 0x08 0x00
> > cmd->result = 0x00000000
> > good_bytes == old_good_bytes = 0x800  scsi_get_resid(cmd) = 0x800
> > New good_bytes = 0x0
> > scsi_finish_command: Complete
> > 
> > From here it just keeps repeating this read of 8 blocks. (2048 bytes) so
> > it looks like the machine is hung.
> 
> Probably not hung, just doing a lot of retries.  It should time out 
> eventually, but it might take a long time (perhaps as long as 15 
> minutes).  The combination of the block layer and the SCSI layer isn't 
> very good at knowing when to give up.

Actually, I think this is a partition read.  Each partition manager
tends to read a page through the page cache.  If we get an error, we
seem to re-read to fill the cache.

> > Now, I know for a fact that _if_ this read CDB is actually being sent to
> > the drive, it's actual residual count will be zero. These are working
> > disks and that read CDB is valid.
> > 
> > Why is ahc_calc_residual saying that the residual count is as though the
> > read never took place? I noticed that the first read on all the SATA
> > drives was for 4096 bytes, why is this one only 2048? Should it have
> > been 4096 and ahc_calc_residual assume that?
> 
> I don't know the answer to any of these questions.  They could well be
> due to bugs in the driver, and I know nothing about how the aic7xxx
> driver works.  You should talk to someone who does.

I'll take this one ... although we're a bit lacking in documentation for
this driver.

I think the 2048 is because something is hardcoded to think 8 sectors is
a page.

James

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