RE: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices

[Michael Kelley (EOSG)]

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx <linux-kernel-owner@xxxxxxxxxxxxxxx> On Behalf
> Of Long Li
> Sent: Thursday, March 22, 2018 2:47 PM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen
> Hemminger <sthemmin@xxxxxxxxxxxxx>; James E . J . Bottomley <JBottomley@xxxxxxxx>;
> Martin K . Petersen <martin.petersen@xxxxxxxxxx>; devel@xxxxxxxxxxxxxxxxxxxxxx; linux-
> scsi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Cc: Long Li <longli@xxxxxxxxxxxxx>
> Subject: [PATCH v2] storvsc: Set up correct queue depth values for IDE devices
> 
> From: Long Li <longli@xxxxxxxxxxxxx>
> 
> Unlike SCSI and FC, we don't use multiple channels for IDE.
> Also fix the calculation for sub-channels.
> 
> Change log:
> v2: Addressed comment on incorrect number of sub-channels.
> (Michael Kelley <Michael.H.Kelley@xxxxxxxxxxxxx>)
> 
> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>

> ---
>  drivers/scsi/storvsc_drv.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 8c51d628b52e..a2ec0bc9e9fa 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1722,11 +1722,14 @@ static int storvsc_probe(struct hv_device *device,
>  		max_targets = STORVSC_MAX_TARGETS;
>  		max_channels = STORVSC_MAX_CHANNELS;
>  		/*
> -		 * On Windows8 and above, we support sub-channels for storage.
> +		 * On Windows8 and above, we support sub-channels for storage
> +		 * on SCSI and FC controllers.
>  		 * The number of sub-channels offerred is based on the number of
>  		 * VCPUs in the guest.
>  		 */
> -		max_sub_channels = (num_cpus / storvsc_vcpus_per_sub_channel);
> +		if (!dev_is_ide)
> +			max_sub_channels =
> +				(num_cpus - 1) / storvsc_vcpus_per_sub_channel;
>  	}
> 
>  	scsi_driver.can_queue = (max_outstanding_req_per_channel *
> --
> 2.14.1