On 05/03/2018 04:40 PM, Bryant G. Ly wrote:
>
> On 5/3/18 12:53 PM, Lee Duncan wrote:
>
>> When a tape drive is exported via LIO using the
>> pscsi module, a read that requests more bytes per block
>> than the tape can supply returns an empty buffer. This
>> is because the pscsi pass-through target module sees
>> the "ILI" illegal length bit set and thinks there
>> is no reason to return the data.
>>
>> Add in a hack to check for tape reads with the INI
>> bit set, treating such cases as if there is no
>> sense data. The tape driver then "does the right
>> thing" when it gets the INI bit and that date.
>>
>> ...
>>
>> diff --git a/drivers/target/target_core_transport.c
>> b/drivers/target/target_core_transport.c
>> index 836d552b0385..aafd64b514fe 100644
>> --- a/drivers/target/target_core_transport.c
>> +++ b/drivers/target/target_core_transport.c
>> @@ -2187,7 +2187,25 @@ static void target_complete_ok_work(struct
>> work_struct *work)
>> * the struct se_cmd in question.
>> */
>> if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) {
>> + struct se_device *dev = cmd->se_dev;
>> + unsigned char *sense = cmd->sense_buffer;
>> +
>> WARN_ON(!cmd->scsi_status);
>> +
>> + /*
>> + * hack: check for tape reads with the ILI (illegal
>> + * length indicator) set, and just pass those through
>> + */
>> + if ((dev->transport->get_device_type(dev) == TYPE_TAPE) &&
>> + (cmd->scsi_status == SAM_STAT_CHECK_CONDITION) &&
>> + (cmd->data_direction == DMA_FROM_DEVICE)) {
>> + if ((sense[0] == 0xf0) && /* 'valid' and 'fixed
>> format' */
>> + (sense[2] & 0x20)) { /* 'ILI' */
>> + pr_debug("Tape ILI Bit detected. Treating as OK\n");
>> + goto treat_as_normal_read;
>>
> Is this an incomplete patch? I don't see this function
> having the goto treat_as_normal_read?
Yes, the patch was malformed.
>
> But I'd prob just move this code into target_core_pscsi then
> just set a flag so that this function can just look for that flag.
> That way it looks less like of a hack.
>
> if (cmd->se_cmd_flags & NEWFLAG) goto treat_as_normal_read;
>
> -Bryant
I will re-spin a new version and resubmit. Thank you for the suggestion.
--
Lee Duncan
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