[PATCH v6 0/2] fixup handling of timeouts with deferred QCs

This patch series fixes libata and libsas to correctly handles deferred
queued commands in case of a timeout error, to avoid excessive delays in
waking up the scsi EH task.

Igor,

My apologies for the churn, but please retest!
Also, I added your Signed-off-by on patch 2 since half of it is yours.

Martin,

Once reviewed, I or you can take both patches ?

Changes from v5:
 - Reworked patch 1 to have deferred command retries all go through libata
   EH to ensure that we do not run into issues with the block layer
   immediately re-issuing retried deffered commands (which would create
   again the problem we are trying to solve). This change necessitate the
   introduction of a new QC flag and changes to the completion path for
   commands to ATAPI devices.

Changes from v4:
 - Simplified sas_eh_timed_out() code in patch 2

Changes from v3:
 - Reimplement ata_scsi_requeue_deferred_qc() in patch 1 as
   ata_eh_retry_deferred_qc() so that all requeue pathes use the same
   function.

Changes from v2:
 - Modified patch 1 to avoid the problem reported by Sashiko that requeued
   deferred QCs may be re-ssued immediately by the block layer, thus
   potentially keeping the device busy. The modification now relies on
   libata-EH to perform the requeue instead of immediately doing it from
   the eh_timed_out operation.
 - Modified patch 2 to use the new helper function defined in patch 1.

Changes from v1:
 - Modified patch 1 to ignore timed out deferred QCs in
   ata_scsi_requeue_deferred_qc() to let ata_scsi_cmd_error_handler()
   correctly handle this case.

Damien Le Moal (2):
  ata: libata-scsi: terminate deferred commands on time out
  scsi: libsas: terminate deferred commands on time out

 drivers/ata/libata-eh.c             | 48 +++++++++++----
 drivers/ata/libata-scsi.c           | 94 ++++++++++++++++++++++++++---
 drivers/ata/libata.h                |  2 +-
 drivers/scsi/libsas/sas_scsi_host.c | 15 +++++
 include/linux/libata.h              |  4 ++
 include/scsi/libsas.h               |  2 +
 6 files changed, 142 insertions(+), 23 deletions(-)

-- 
2.55.0