Re: [PATCH v5 2/4] ata: libata-scsi: do not use the deferred QC feature for ATA_DEFER_PORT

[Damien Le Moal <dlemoal@kernel.org>]

On 2026/05/14 9:39, Niklas Cassel wrote:
> The deferred QC feature was meant to handle mixed NCQ and non-NCQ commands,
> i.e. for return value ATA_DEFER_LINK.
> 
> ATA_DEFER_PORT is returned by PATA drivers, but also certain SATA drivers
> like sata_mv and sata_sil24 that uses ap->excl_link to workaround hardware
> bugs in these HBAs. Regardless of the reason, using the deferred QC feature
> for ATA_DEFER_PORT is always wrong, and will break the ap->excl_link usage
> of the SATA drivers that rely on that feature.
> 
> Modify ata_scsi_qc_issue() to only use the deferred QC feature when mixing
> NCQ and non-NCQ commands, i.e. ATA_DEFER_LINK.
> 
> Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

Looks good.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>


-- 
Damien Le Moal
Western Digital Research