Re: [PATCH RFC v3 2/7] ata: libata-scsi: Add ata_internal_queuecommand()

Damien Le Moal
2022-10-27T22:26:07Z

On 10/27/22 18:56, John Garry wrote:
> On 27/10/2022 02:45, Damien Le Moal wrote:
>> On 10/25/22 19:32, John Garry wrote:
>>> Add callback to queue reserved commands - call it "internal" as this is
>>> what libata uses.
>>>
>>> Also add it to the base ATA SHT.
>>>
>>> Signed-off-by: John Garry <john.garry@huawei.com>
>>> ---
>>> drivers/ata/libata-scsi.c | 14 ++++++++++++++
>>> include/linux/libata.h | 5 ++++-
>>> 2 files changed, 18 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
>>> index 30d7c90b0c35..0d6f37d80137 100644
>>> --- a/drivers/ata/libata-scsi.c
>>> +++ b/drivers/ata/libata-scsi.c
>>> @@ -1118,6 +1118,20 @@ int ata_scsi_dev_config(struct scsi_device *sdev, struct ata_device *dev)
>>> return 0;
>>> }
>>>
>>> +int ata_internal_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmd)
>>> +{
>>> + struct ata_port *ap;
>>> + int res;
>>> +
>>> + ap = ata_shost_to_port(shost);
>>
>> You can have this initialization together with the ap declaration.
>>
>>> + spin_lock_irq(ap->lock);
>>> + res = ata_sas_queuecmd(scmd, ap);
>>> + spin_unlock_irq(ap->lock);
>>> +
>>> + return res;
>>> +}
>>> +EXPORT_SYMBOL_GPL(ata_internal_queuecommand);
>>
>> I am officially lost here. Do not see why this function is needed...
>
> The general idea in this series is to send ATA internal commands as
> requests. And this function is used as the SCSI midlayer to queue
> reserved commands. See how it is plugged into __ATA_BASE_SHT, below.
>
> So we have this overall flow:
>
> ata_exec_internal_sg():
> -> alloc request
> -> blk_execute_rq_nowait()
> ... -> scsi_queue_rq()
> -> sht->reserved_queuecommd()
> -> ata_internal_queuecommand()
>
> And then we have ata_internal_queuecommand() -> ata_sas_queuecmd() ->
> ata_scsi_queue_internal() -> ata_qc_issue().
>
> Hope it makes sense.

OK. Got it.
However, ata_exec_internal_sg() being used only from EH context with the
queue quiesced, will blk_execute_rq_nowait() work ? Is there an exception
for internal reserved tags ?

>
> Thanks,
> John
>
>>
>>> +
>>> /**
>>> * ata_scsi_slave_config - Set SCSI device attributes
>>> * @sdev: SCSI device to examine
>>> diff --git a/include/linux/libata.h b/include/linux/libata.h
>>> index 8938b584520f..f09c5dca16ce 100644
>>> --- a/include/linux/libata.h
>>> +++ b/include/linux/libata.h
>>> @@ -1141,6 +1141,8 @@ extern int ata_std_bios_param(struct scsi_device *sdev,
>>> sector_t capacity, int geom[]);
>>> extern void ata_scsi_unlock_native_capacity(struct scsi_device *sdev);
>>> extern int ata_scsi_slave_config(struct scsi_device *sdev);
>>> +extern int ata_internal_queuecommand(struct Scsi_Host *shost,
>>> + struct scsi_cmnd *scmd);
>>> extern void ata_scsi_slave_destroy(struct scsi_device *sdev);
>>> extern int ata_scsi_change_queue_depth(struct scsi_device *sdev,
>>> int queue_depth);
>>> @@ -1391,7 +1393,8 @@ extern const struct attribute_group *ata_common_sdev_groups[];
>>> .slave_destroy = ata_scsi_slave_destroy, \
>>> .bios_param = ata_std_bios_param, \
>>> .unlock_native_capacity = ata_scsi_unlock_native_capacity,\
>>> - .max_sectors = ATA_MAX_SECTORS_LBA48
>>> + .max_sectors = ATA_MAX_SECTORS_LBA48,\
>>> + .reserved_queuecommand = ata_internal_queuecommand
>>>
>>> #define ATA_SUBBASE_SHT(drv_name) \
>>> __ATA_BASE_SHT(drv_name), \
>>
>

--
Damien Le Moal
Western Digital Research