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

Hannes Reinecke
2022-10-27T13:03:06Z

On 10/27/22 11:56, 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.
>
> 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),                \
>>
>

But that means we can't use it before the SCSI host is initialized; some
HBAs require to send commands before the host can be initialized properly.

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
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