Re: [PATCH 07/13] sd: Translate data lifetime information

[Bart Van Assche <bvanassche@acm.org>]

On 10/2/23 06:11, Avri Altman wrote:
>> sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
>>                  ret = sd_setup_rw16_cmnd(cmd, write, lba, nr_blocks,
>>                                           protect | fua, dld);
>>          } else if ((nr_blocks > 0xff) || (lba > 0x1fffff) ||
>> -                  sdp->use_10_for_rw || protect) {
>> +                  sdp->use_10_for_rw || protect ||
>> +                  rq->write_hint != WRITE_LIFE_NOT_SET) {
>
> Is this a typo?

I don't see a typo? Am I perhaps overlooking something?

>> +static void sd_read_io_hints(struct scsi_disk *sdkp, unsigned char *buffer)
>> +{
>> +       struct scsi_device *sdp = sdkp->device;
>> +       const struct scsi_io_group_descriptor *desc, *start, *end;
>> +       struct scsi_sense_hdr sshdr;
>> +       struct scsi_mode_data data;
>> +       int res;
>> +
>> +       res = scsi_mode_sense(sdp, /*dbd=*/0x8, /*modepage=*/0x0a,
>> +                             /*subpage=*/0x05, buffer, SD_BUF_SIZE,
>> +                             SD_TIMEOUT, sdkp->max_retries, &data, &sshdr);
>> +       if (res < 0)
>> +               return;
>> +       start = (void *)buffer + data.header_length + 16;
>> +       end = (void *)buffer + ((data.header_length + data.length)
>> +                               & ~(sizeof(*end) - 1));
>> +       /*
>> +        * From "SBC-5 Constrained Streams with Data Lifetimes": Device severs
>> +        * should assign the lowest numbered stream identifiers to permanent
>> +        * streams.
>> +        */
>> +       for (desc = start; desc < end; desc++)
>> +               if (!desc->st_enble)
>> +                       break;
> I don't see how you can conclude that the stream is permanent,
> without reading the perm bit from the stream status descriptor.

I will add code that retrieves the stream status and that checks the 
PERM bit.

>> diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
>> index 84685168b6e0..1863de5ebae4 100644
>> --- a/drivers/scsi/sd.h
>> +++ b/drivers/scsi/sd.h
>> @@ -125,6 +125,7 @@ struct scsi_disk {
>>          unsigned int    physical_block_size;
>>          unsigned int    max_medium_access_timeouts;
>>          unsigned int    medium_access_timed_out;
>> +       u16             permanent_stream_count; /* maximum number of streams
>> */
>
> This comment is a bit misleading:
> The Block Limits Extension VPD page has a "maximum number of streams" field.
> Maybe avoid the unnecessary confusion?

I will change that comment or leave it out.

Thanks,

Bart.