linux-kernel - Re: TRIM/UNMAP/DISCARD via ATA Passthrough

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Message-ID: <5af202ea-a632-28c2-515f-c361e27de5da@suse.de>
Date:   Fri, 16 Sep 2016 13:16:35 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: TRIM/UNMAP/DISCARD via ATA Passthrough

On 09/15/2016 10:52 PM, Jason A. Donenfeld wrote:
> Hi Martin,
> 
> On Thu, Sep 15, 2016 at 6:07 PM, Martin K. Petersen
>> But how do they signal that ATA passthrough is possible? Is there an ATA
>> Information VPD page? Is REPORT SUPPORTED OPERATION CODES supported?
>>
>> We need really solid discovery data before we can entertain enabling
>> something like this.
> 
> `sg_opcodes` said invalid request, so I think there isn't REPORT
> SUPPORTED OPERATION CODES, and `sg_vpd -p ai` came up illegal too.
> 
> However, sg_sat_identify worked reliably, which means a solid way of
> probing this would be to send IDENTIFY DEVICE ATA via SG_ATA_16 or
> SG_ATA_12.
> 
> Let me know and I can give you access to the hardware if you're curious.
> 
Sadly, that's not sufficient.
linux is not the only provider of an SATL (mpt3sas being the most
prominent other one).
And while they might support ATA_12/ATA_16, there is no indication that
you can pass DSM TRIM that way.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@...e.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)