Commands using a duration limit descriptor that has limit policies set to a
value other than 0x0 may be failed by the device if one of the limits are
exceeded. For such commands, since the failure is the result of the user
duration limit configuration and workload, the commands should not be
retried and terminated immediately. Furthermore, to allow the user to
differentiate these "soft" failures from hard errors due to hardware
problem, a different error code than EIO should be returned.

There are 2 cases to consider:

(1) The failure is due to a limit policy failing the command with a check
condition sense key, that is, any limit policy other than 0xD.  For this
case, scsi_check_sense() is modified to detect failures with the ABORTED
COMMAND sense key and the COMMAND TIMEOUT BEFORE PROCESSING or COMMAND
TIMEOUT DURING PROCESSING or COMMAND TIMEOUT DURING PROCESSING DUE TO ERROR
RECOVERY additional sense code. For these failures, a SUCCESS disposition
is returned so that scsi_finish_command() is called to terminate the
command.

(2) The failure is due to a limit policy set to 0xD, which result in the
command being terminated with a GOOD status, COMPLETED sense key, and DATA
CURRENTLY UNAVAILABLE additional sense code. To handle this case, the
scsi_check_sense() is modified to return a SUCCESS disposition so that
scsi_finish_command() is called to terminate the command.  In addition,
scsi_decide_disposition() has to be modified to see if a command being
terminated with GOOD status has sense data.  This is as defined in SCSI
Primary Commands - 6 (SPC-6), so all according to spec, even if GOOD status
commands were not checked before.

If scsi_check_sense() detects sense data representing a duration limit,
scsi_check_sense() will set the newly introduced SCSI ML byte
SCSIML_STAT_DL_TIMEOUT. This SCSI ML byte is checked in scsi_noretry_cmd(),
so that a command that failed because of a CDL timeout cannot be
retried. The SCSI ML byte is also checked in scsi_result_to_blk_status() to
complete the command request with the BLK_STS_DURATION_LIMIT status, which
result in the user seeing ETIME errors for the failed commands.
Co-developed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Link: https://lore.kernel.org/r/20230511011356.227789-12-nks@flawful.orgSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>