Hi Bart,
On Sat, 2020-07-18 at 13:30 -0700, Bart Van Assche wrote:
> On 2020-07-17 00:39, Lee Sang Hyun wrote:
> > - ret = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL, &sshdr,
> > - START_STOP_TIMEOUT, 0, 0, RQF_PM, NULL);
> > - if (ret) {
> > - sdev_printk(KERN_WARNING, sdp,
> > - "START_STOP failed for power mode: %d, result %x\n",
> > - pwr_mode, ret);
> > - if (driver_byte(ret) == DRIVER_SENSE)
> > - scsi_print_sense_hdr(sdp, NULL, &sshdr);
> > + for (retries = 0; retries < SSU_RETRIES; retries++) {
> > + ret = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL, &sshdr,
> > + START_STOP_TIMEOUT, 0, 0, RQF_PM, NULL);
> > + if (ret) {
> > + sdev_printk(KERN_WARNING, sdp,
> > + "START_STOP failed for power mode: %d, result %x\n",
> > + pwr_mode, ret);
> > + if (driver_byte(ret) == DRIVER_SENSE)
> > + scsi_print_sense_hdr(sdp, NULL, &sshdr);
> > + } else {
> > + break;
> > + }
>
> The ninth argument of scsi_execute() is called 'retries'. Wouldn't it be
> better to pass a nonzero value as the 'retries' argument of
> scsi_execute() instead of adding a loop around the scsi_execute() call?
If a SCSI command issued via scsi_execute() encounters "timeout" or
"check condition", scsi_noretry_cmd() will return 1 (true) because
blk_rq_is_passthrough() is true due to REQ_OP_SCSI_IN or REQ_OP_SCSI_OUT
flag was set to this SCSI command by scsi_execute(). Therefore even a
non-zero 'retries' value is assigned while calling scsi_execute(), the
failed command has no chance to be retried since the decision will be
no-retry by scsi_noretry_cmd().
(Take command timeout as example)
scsi_times_out()->scsi_abort_command()->scmd_eh_abort_handler(), here
scsi_noretry_cmd() returns 1, and then command will be finished (with
error code) without retry.
In scsi_noretry_cmd(), there is a comment message in section
"check_type" as below
/*
* assume caller has checked sense and determined
* the check condition was retryable.
*/
I am not sure if "timeout" and "check condition" cases in such SCSI
commands issued via scsi_execute() are specially designed to be unable
to retry.
Would you have any suggestions if LLD drivers would like to retry these
kinds of SCSI commands?
Thanks a lot,
Stanley Chu
