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Subject: Re: [PATCH v2] ata: libata-scsi: Fix get identity data failed
To:     Damien Le Moal <dlemoal@kernel.org>,
        yangxingui <yangxingui@huawei.com>, <jejb@linux.ibm.com>,
        <martin.petersen@oracle.com>, <john.g.garry@oracle.com>
CC:     <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linuxarm@huawei.com>, <prime.zeng@hisilicon.com>,
        <kangfenglong@huawei.com>
References: <20230505025712.19438-1-yangxingui@huawei.com>
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 <02d36ee9-cdad-454d-d822-95442d7bd67b@huawei.com>
 <f4ba7a92-1f00-c254-d196-7d21fe14dee2@kernel.org>
 <938d6b5b-0271-977d-f046-5fd70d29b3ca@huawei.com>
 <a5c2e157-aaf7-1300-3fbb-1300ac216cee@kernel.org>
 <68953040-1622-254b-f6f8-b279eccacfb1@kernel.org>
From:   Jason Yan <yanaijie@huawei.com>
Message-ID: <c88dcbc3-d530-3e9e-f674-a2fe64ad5fdc@huawei.com>
Date:   Mon, 22 May 2023 16:00:32 +0800
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On 2023/5/22 15:02, Damien Le Moal wrote:
> On 5/22/23 10:35, Damien Le Moal wrote:
>> On 5/8/23 10:11, yangxingui wrote:
>>>
>>>
>>> On 2023/5/7 22:51, Damien Le Moal wrote:
>>>> On 2023/05/05 18:06, yangxingui wrote:
>>>>>
>>>>>
>>>>> On 2023/5/5 16:17, Damien Le Moal wrote:
>>>>>> On 2023/05/05 11:57, Xingui Yang wrote:
>>>>>>> The function ata_get_identity() uses the helper ata_scsi_find_dev() to get
>>>>>>> the ata_device structure of a scsi device. However, when the ata device is
>>>>>>> managed by libsas, ata_scsi_find_dev() returns NULL, turning
>>>>>>> ata_get_identity() into a nop and always returns -ENOMSG.
>>>>>>
>>>>>> What do you do to hit the issue ? A while back for me it was the queue depth
>>>>>> setting causing problems. As Garry mentioned, this led to patch 141f3d6256e5
>>>>>> ("ata: libata-sata: Fix device queue depth control").
>>>>> Attempt to return the correct value at ata_scsi_find_dev() instead of
>>>>> NULL, when the ata device is managed by libsas?
>>>>
>>>> That I understand. My question is *what* user operation/command triggers this ?
>>>> Because on my test setup, under normal use, I do not see this issue (beside what
>>>> was already corrected with the queue depth control). Is the issue showing up
>>>> when using passthrough commands only ?
>>> Yeah, we found that command "hdparm -i /dev/sdc" always return faild for
>>> SATA HDD disk. as follows:
>>> [root@localhost ~]# hdparm -i /dev/sdc
>>>
>>> /dev/sdc:
>>>    HDIO_GET_IDENTITY failed: Invalid argument
>>
>> I cannot recreate this issue exactly like this. Here is my setup with a pm80xx
>> driver (Adaptec HBA):
>>
>> [7:0:0:0]    disk    ATA      WDC  WUH721818AL W232  /dev/sdd   /dev/sg5
>> [7:0:1:0]    disk    ATA      WDC  WUH721818AL WTW2  /dev/sdi   /dev/sg6
>> [7:0:2:0]    disk    ATA      WDC  WUH722222AL Wf86  /dev/sdf   /dev/sg7
>> [7:0:3:0]    zbc     ATA      WDC  WSH722020AL W803  /dev/sdg   /dev/sg8
>>
>> Using the first drive, I get:
>>
>> sudo hdparm -i /dev/sdd
>>
>> /dev/sdd:
>>
>>   Model=WDC  WUH721818ALN604, FwRev=PCGNW232, SerialNo=3KG10LBK
>>   Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
>>   RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=56
>>   BuffType=DualPortCache, BuffSize=unknown, MaxMultSect=2, MultSect=off
>>   CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=4394582016
>>   IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
>>   PIO modes:  pio0 pio1 pio2 pio3 pio4
>>   DMA modes:  mdma0 mdma1 mdma2
>>   UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
>>   AdvancedPM=yes: disabled (255) WriteCache=enabled
>>   Drive conforms to: unknown:  ATA/ATAPI-2,3,4,5,6,7
>>
>>   * signifies the current active mode
>>
>> So all good. However, for the following drives, I get:
>>
>> sudo hdparm -i /dev/sdi
>>
>> /dev/sdi:
>>   HDIO_GET_IDENTITY failed: No message of desired type
>>
>> (same for sdf and sdg).
>>
>> Will dig into this.
> 
> OK, so the issue is that __ata_scsi_find_dev() calls ata_find_dev() with devno
> == scsidev->id. This leads to devno being 0, 1, 2 and 3 for connected drives
> sdd, sd1, sdf and sdg, as shown by lsscsi. However, each drive has its own
> port+link, with the link for each one having  ata_link_max_devices() == 1, so
> ata_find_dev() works only for the first drive with scsidev->id == 0 and fails
> for the others. A naive fix would be this:
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 7bb12deab70c..e4d6f17d7ccc 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -2718,7 +2718,7 @@ static struct ata_device *__ata_scsi_find_dev(struct
> ata_port *ap,
>          if (!sata_pmp_attached(ap)) {
>                  if (unlikely(scsidev->channel || scsidev->lun))
>                          return NULL;
> -               devno = scsidev->id;
> +               devno = 0;
>          } else {
>                  if (unlikely(scsidev->id || scsidev->lun))
>                          return NULL;
> 
> And running this on my setup, it works. This makes libsas added ports/devices
> look like AHCI ones, where all devices have ID 0 for the !pmp case.
> 
> However, I am not sure this would be OK for all setups...
> 
> John,
> 
> Any idea if there is any cases where libsas managed drives would endup not being
> correctly identified by this change ? As long as a device always has its own
> port, I do not see any issue. But is there a case where we could have multiple
> devices on the same port ? Per libata, max is 2, and that is only for the IDE
> master/slave case. Otherwise, it is always 1.
> 

AFAIK, libsas does not support multiple devices on the same port. So 
this change is ok for libsas.

> Not that looking at the pmp case, I am not confident at all that the
> identification is correct for libsas. But I do not think that anyone would ever
> connect a pmp box to a libsas HBA...
> 

libsas's does not support pmp either, and I do not see any future plans 
to support pmp.

So the above change (needs a ATA_FLAG_SAS_HOST check) looks good to me.
It's better to make libsas behave as other ata drivers so that we can 
drop the ATA_FLAG_SAS_HOST check. But this need tons of work for libsas.

Thanks,
Jason