Re: [PATCH v2] ata: libata-scsi: Fix get identity data failed

yangxingui
2023-05-06T09:57:20Z

On 2023/5/5 17:51, John Garry wrote:
> On 05/05/2023 10:14, yangxingui wrote:
>>> hmmm... is it really acceptable that libata is referencing libsas? I
>>> didn't think that it would be. libsas uses libata, not the other way
>>> around.
>> Yeah, I didn't expect that either. Is there any other way? If so, is
>> patch v1 OK?
>
> I still think that we can do better than v1.
OK
>
>>>
>>>>>   #include <linux/libata.h>
>>>>>   #include <linux/hdreg.h>
>>>>>   #include <linux/uaccess.h>
>>>>> @@ -2745,10 +2746,17 @@ static struct ata_device
>>>>> *__ata_scsi_find_dev(struct ata_port *ap,
>>>>>    *    Associated ATA device, or %NULL if not found.
>>>>>    */
>>>>>   struct ata_device *
>>>>> -ata_scsi_find_dev(struct ata_port *ap, const struct scsi_device
>>>>> *scsidev)
>>>> Why drop the const ?
>>>>
>>>>> +ata_scsi_find_dev(struct ata_port *ap, struct scsi_device *scsidev)
>>>>>   {
>>>>> -    struct ata_device *dev = __ata_scsi_find_dev(ap, scsidev);
>>>>> +    struct ata_device *dev;
>>>>> +
>>>>> +    if (ap->flags & ATA_FLAG_SAS_HOST) {
>>>
>>> And this is SAS host. Not necessarily libsas (even though with ipr
>>> libata usage gone, it would be the only user).
>> Add a new flag only for libsas?
>
> No, because of previous reason.
>
> Please remind me - at what point do we error within ata_scsi_find_dev()
> and return NULL for a libsas host?
The scsi_host_template filled by libsas and call ata_scsi_find_dev() has
this problem. After sas_change_queue_depth() is fixed, only sas_ioctl()
has this problem now.
>
> Note: it would be good to include that commit message for future reference.
>
> Maybe we could add a method to ata_port_operations to do this lookup. I
> assume that is abusing ata_port_operations purpose, since it's mostly
> for HW methods.
>
> Or do we actually use sdev->hostdata for libata or libsas? If not, maybe
> we could store the struct ata_device pointer there.
Well, it might be a way.

Thanks,
Xingui
.
>
> I'm just thinking out loud now...
>
> Thanks,
> John
>
>
> .