libata EH appears to be NFG up to 2.6.17 (at least).

[Mark Lord <liml@rtr.ca>]

Got your attention now?  Good!

I am doing some testing with known-bad drives on 2.6.16 (and 2.6.17).

Libata EH is wretched there, because it does not seem to be careful
about reading/saving the bad ata_status value when an error occurs.

The ata_status from a failed/aborted command is first read in
the interrupt handler, either by the LLD or by ata_host_intr().

This value is not saved for reuse anywhere, and the next time it is read,
the reader will see ATA_ERR==0, and then not do the Right Thing (tm).

Who reads it next, you ask?  Well, it gets read *again* from libata-scsi
when it is trying to generate meaningful sense data.  But at that point,
all that is seen is 0x50 -- "success".

So libata-scsi returns incorrect (or no) sense data to the SCSI mid-layer,
and the error is mishandled or ignored.

Ugh.  The distro folks will probably want to fix this in their 2.6.1[56]
based distro kernels.  I don't yet see a way to do this without modifying
core data structures (eg. adding an ata_status field to the qc).

Any ideas?