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Message-ID: <3ef0347f-f3e2-cf08-2b27-f65a7afe82a2@suse.de>
Date:   Thu, 27 Oct 2022 15:02:59 +0200
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Subject: Re: [PATCH RFC v3 2/7] ata: libata-scsi: Add
 ata_internal_queuecommand()
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To:     John Garry <john.garry@huawei.com>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        jejb@linux.ibm.com, martin.petersen@oracle.com, bvanassche@acm.org,
        hch@lst.de, ming.lei@redhat.com, niklas.cassel@wdc.com
Cc:     axboe@kernel.dk, jinpu.wang@cloud.ionos.com,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org,
        linuxarm@huawei.com
References: <1666693976-181094-1-git-send-email-john.garry@huawei.com>
 <1666693976-181094-3-git-send-email-john.garry@huawei.com>
 <08fdb698-0df3-7bc8-e6af-7d13cc96acfa@opensource.wdc.com>
 <83d9dc82-ea37-4a3c-7e67-1c097f777767@huawei.com>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <83d9dc82-ea37-4a3c-7e67-1c097f777767@huawei.com>
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Precedence: bulk

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
hare@suse.de                              +49 911 74053 688
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