On 12 August 2016 at 13:18, Tom Yan <tom.t...@gmail.com> wrote:
> On 12 August 2016 at 10:01, Martin K. Petersen
> <martin.peter...@oracle.com> wrote:
>>
>> Again, the point of max_hw_sectors and max_dev_sectors is to enforce the
>> hard limits of controller and device respectively. Nothing else.
>>
>
> Sounds like libata-scsi is doing something wrong then. It should not
> set max_hw_sectors to dev->max_sectors that is set by libata-core:
>
>> blk_queue_max_hw_sectors(q, dev->max_sectors);

Though we'll still have to "abuse" max_hw_sectors for ATAPI class
devices, since neither the SATL or sr cares about VPD. The only
devices that need ATA_HORKAGE_MAX_SEC_LBA48 are ATAPI devices as well.

>
> but instead it should report it as Maximum Transfer Length and let sd
> set it as max_dev_sectors:
>
>> put_unaligned_be32(dev->max_sectors, &rbuf[8]);
>
> While max_hw_sectors will be left untouched (in the case of AHCI, for
> example, since its SCSI host template does not have max_sectors set;
> so max_hw_sectors will be SCSI_DEFAULT_MAX_SECTORS).
>
> Although that means setting dev->max_sectors to a value larger than
> 1024 will probably be a no-op, if that's really an issue, we should
> have the host templates in libata updated.
>
> Make sense?
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