Fix the `tape drive spinning indefinately upon mt stat' problem.

With the recent changes in the CAM error handling, some problems in
the error handling of sa(4) have been uncovered.  Basically, a number
of conditions that are not actually errors have been mistreated as
genuine errors.  In particular:

. Trying to read in variable length mode with a mismatched blocksize
  between the on-tape (virtual) blocks and the read(2) supplied buffer
  size, causing an ILI SCSI condition, have caused an attempt to retry
  the supposedly `errored' transfer, causing the tape to be read
  continuously until it eventually hit EOM.  Since by default any
  simple mt(1) operation does an initial test read, an `mt stat' was
  sufficient to trigger this bug.

  Note that it's Justin's opinion that treating a NO SENSE as an EIO
  is another bug in CAM.  I feel not authorized to fix cam_periph.c
  without another confirmation that i'm on the right track, however.

. Hitting a filemark caused the read(2) syscall to return EIO, instead
  of returning a `short read'.  Note that the current fix only solves
  this problem in variable length mode.  Fixed length mode uses a
  different code path, and since i didn't grok all the intentions behind
  that handling, i did not touch it (IOW: it's still broken, and you get
  an EIO upon hitting a filemark).

The solution is to keep track of those conditions inside saerror(),
and upon completion to not call cam_periph_error() in that case.  We
need to make sure that the device gets unfrozen if needed though (in
case of actual errors, cam_periph_error() does this on our behalf).

Not objected by:       mjacob (who currently doesn't have the time to
			      review the patch)

0 files changed, 0 insertions, 0 deletions