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

[Jason Yan]

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