I am working on the assumption that users of the
SG_IO ioctl in the block layer (or via st or osst)
want SCSI status and sense data returned
via the ioctl immediately without:
   - the error/warning silently disappearing and/or being
     hidden by a retry (e.g. UNIT ATTENTION, lu becoming
     ready)
   - noise in the log (or console)
   - any other side effects (save clearing expecting_cc_ua
     if a UNIT ATTENTION was expected)

To this end here are two patches, the first to scsi_lib.c
attached to this post and the second to sd.c in a following
post. Some work may also be needed in the st and osst
drivers.

These patches are against lk 2.6.11-rc1-bk1 which includes
James's "SCSI updates to 2.6.11-rc1" patch.

The descriptor sense patches are now functional in
the mid level (including error reporting functions
in constants.c). The next drivers to visit will be
sd and sg. Medium errors (or hardware errors which seem
synonomous) are an interesting case for sd with big
lus. SBC-2 says that if the sense data information field
is too large to fit in the fixed format sense data then
the valid bit shall be set to 0. This implies big lus
really should be using descriptor sense format.

Changelog:
   - cleanup scsi_end_request() documentation
   - shorten path for block SG_IO through scsi_io_completion()
   - for non-SG_IO sense processing in scsi_io_completion():
      - ignore deferred errors (report + retry should suffice)
      - consolidate into a cleaner switch statement

Signed-off-by: Douglas Gilbert <dougg@torque.net>