[PATCH v1 2/3] scsi: ufs: Optimize host lock on transfer requests send/compl paths

[Bart Van Assche]

On 5/24/21 1:36 AM, Can Guo wrote:
> @@ -2688,6 +2705,43 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
> +	case UFSHCD_STATE_EH_SCHEDULED_FATAL:
> +		/*
> +		 * pm_runtime_get_sync() is used at error handling preparation
> +		 * stage. If a scsi cmd, e.g. the SSU cmd, is sent from hba's
> +		 * PM ops, it can never be finished if we let SCSI layer keep
> +		 * retrying it, which gets err handler stuck forever. Neither
> +		 * can we let the scsi cmd pass through, because UFS is in bad
> +		 * state, the scsi cmd may eventually time out, which will get
> +		 * err handler blocked for too long. So, just fail the scsi cmd
> +		 * sent from PM ops, err handler can recover PM error anyways.
> +		 */
> +		if (hba->pm_op_in_progress) {
> +			hba->force_reset = true;
> +			set_host_byte(cmd, DID_BAD_TARGET);
> +			cmd->scsi_done(cmd);
> +			goto out;
> +		}
> +		fallthrough;

Hi Can,

I know that this patch only moves the above code and that the above code
has not been introduced by this patch. Anyway, is my understanding
correct that ufshcd_err_handler() can change the host controller state
from UFSHCD_STATE_EH_SCHEDULED_FATAL into UFSHCD_STATE_RESET and next
into UFSHCD_STATE_OPERATIONAL? If so, if the above code completes a READ
with status DID_BAD_TARGET and if recovery by the error handler
succeeds, will that cause the filesystem above the UFS driver to change
into read-only mode? If the above code completes a WRITE with status
DID_BAD_TARGET, will that cause data corruption? Is there any other
solution to prevent data corruption than merging the
UFSHCD_STATE_EH_SCHEDULED_FATAL and UFSHCD_STATE_EH_SCHEDULED_NON_FATAL
back into a single state and changing the ufshcd_rpm_get_sync(hba) call
in ufshcd_err_handling_prepare() into a pm_runtime_get_noresume() call?

Thanks,

Bart.