s390/zcrypt: introduce msg tracking in zcrypt functions

Introduce a new internal struct zcrypt_track with an retry counter
field and a last return code field. Fill and update these fields at
certain points during processing of an request/reply. This tracking
info is then used to
- avoid trying to resend the message forever. Now each message is
  tried to be send TRACK_AGAIN_MAX (currently 10) times and then the
  ioctl returns to userspace with errno EAGAIN.
- avoid trying to resend the message on the very same card/domain. If
  possible (more than one APQN with same quality) don't use the very
  same qid as the previous attempt when again scheduling the request.
  This is done by adding penalty weight values when the dispatching
  takes place. There is a penalty TRACK_AGAIN_CARD_WEIGHT_PENALTY for
  using the same card as previously and another penalty define
  TRACK_AGAIN_QUEUE_WEIGHT_PENALTY to be considered when the same qid
  as the previous sent attempt is calculated. Both values make it
  harder to choose the very same card/domain but not impossible. For
  example when only one APQN is available a resend can only address the
  very same APQN.

There are some more ideas for the future to extend the use of this
tracking information. For example the last response code at NQAP and
DQAP could be stored there, giving the possibility to extended tracing
and debugging about requests failing to get processed properly.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions