Re: [PATCH] ata: libata-core: fetch sense data for successful commands iff CDL enabled

[Hannes Reinecke <hare@suse.de>]

On 9/13/23 17:04, Niklas Cassel wrote:
> From: Niklas Cassel <niklas.cassel@wdc.com>
> 
> Currently, we fetch sense data for a _successful_ command if either:
> 1) Command was NCQ and ATA_DFLAG_CDL_ENABLED flag set (flag
>     ATA_DFLAG_CDL_ENABLED will only be set if the Successful NCQ command
>     sense data supported bit is set); or
> 2) Command was non-NCQ and regular sense data reporting is enabled.
> 
> This means that case 2) will trigger for a non-NCQ command which has
> ATA_SENSE bit set, regardless if CDL is enabled or not.
> 
> This decision was by design. If the device reports that it has sense data
> available, it makes sense to fetch that sense data, since the sk/asc/ascq
> could be important information regardless if CDL is enabled or not.
> 
> However, the fetching of sense data for a successful command is done via
> ATA EH. Considering how intricate the ATA EH is, we really do not want to
> invoke ATA EH unless absolutely needed.
> 
> Before commit 18bd7718b5c4 ("scsi: ata: libata: Handle completion of CDL
> commands using policy 0xD") we never fetched sense data for successful
> non-NCQ commands.
> 
> In order to not invoke the ATA EH unless absolutely necessary, even if the
> device claims support for sense data reporting, only fetch sense data for
> successful (NCQ and non-NCQ commands) if CDL is supported and enabled.
> 
Errm. We need sense data for zoned devices, do we not?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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