Re: [PATCH] megaraid_sas: Enable shared tag map

[Webb Scales <webbnh@hp.com>]

Hannes,

In megasas_change_queue_type(), is it possible for sdev->queue_depth to 
be greater than 256?

Unless I'm misunderstanding the SCSI code, we can request a 
queue-depth/tag-map-size which is greater than 256, but, since the 
scsi_cmnd::tag field is an unsigned char, depths greater than 256 may 
overflow the field when high-numbered tags are used...do I have that right?


             Thanks,

                 Webb



On 9/29/14 7:47 AM, Hannes Reinecke wrote:
> Megaraid_sas uses a shared pool of commands per HBA, so we
> should be enabling a shared tag map.
> This will allow the I/O scheduler to make better scheduling
> decisions and will avoid BUSY states in the driver.
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
>   drivers/scsi/megaraid/megaraid_sas_base.c | 34 ++++++++++++++++++++++++++++++-
>   1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
> index f6a69a3..996fa9a 100644
> --- a/drivers/scsi/megaraid/megaraid_sas_base.c
> +++ b/drivers/scsi/megaraid/megaraid_sas_base.c
> @@ -1659,7 +1659,7 @@ static int megasas_slave_configure(struct scsi_device *sdev)
>   	*/
>   	blk_queue_rq_timeout(sdev->request_queue,
>   		MEGASAS_DEFAULT_CMD_TIMEOUT * HZ);
> -
> +	sdev->tagged_supported = 1;
>   	return 0;
>   }
>   
> @@ -1667,6 +1667,10 @@ static int megasas_slave_alloc(struct scsi_device *sdev)
>   {
>   	u16             pd_index = 0;
>   	struct megasas_instance *instance ;
> +
> +	/* We have a shared tag map, so TCQ is always supported */
> +	sdev->tagged_supported = 1;
> +
>   	instance = megasas_lookup_instance(sdev->host->host_no);
>   	if (sdev->channel < MEGASAS_MAX_PD_CHANNELS) {
>   		/*
> @@ -1677,13 +1681,20 @@ static int megasas_slave_alloc(struct scsi_device *sdev)
>   			sdev->id;
>   		if (instance->pd_list[pd_index].driveState ==
>   					MR_PD_STATE_SYSTEM) {
> +			scsi_activate_tcq(sdev, MEGASAS_DEFAULT_CMD_PER_LUN);
>   			return 0;
>   		}
>   		return -ENXIO;
>   	}
> +	scsi_activate_tcq(sdev, MEGASAS_DEFAULT_CMD_PER_LUN);
>   	return 0;
>   }
>   
> +static void megasas_slave_destroy(struct scsi_device *sdev)
> +{
> +	scsi_deactivate_tcq(sdev, 1);
> +}
> +
>   void megaraid_sas_kill_hba(struct megasas_instance *instance)
>   {
>   	if ((instance->pdev->device == PCI_DEVICE_ID_LSI_SAS0073SKINNY) ||
> @@ -2746,6 +2757,21 @@ struct device_attribute *megaraid_host_attrs[] = {
>   	NULL,
>   };
>   
> +static int megasas_change_queue_type(struct scsi_device *sdev, int tag_type)
> +{
> +	if (sdev->host->bqt && sdev->tagged_supported) {
> +		scsi_set_tag_type(sdev, tag_type);
> +
> +		if (tag_type)
> +			scsi_activate_tcq(sdev, sdev->queue_depth);
> +		else
> +			scsi_deactivate_tcq(sdev, sdev->queue_depth);
> +	} else
> +		tag_type = 0;
> +
> +	return tag_type;
> +}
> +
>   /*
>    * Scsi host template for megaraid_sas driver
>    */
> @@ -2756,6 +2782,7 @@ static struct scsi_host_template megasas_template = {
>   	.proc_name = "megaraid_sas",
>   	.slave_configure = megasas_slave_configure,
>   	.slave_alloc = megasas_slave_alloc,
> +	.slave_destroy = megasas_slave_destroy,
>   	.queuecommand = megasas_queue_command,
>   	.eh_device_reset_handler = megasas_reset_device,
>   	.eh_bus_reset_handler = megasas_reset_bus_host,
> @@ -2765,6 +2792,7 @@ static struct scsi_host_template megasas_template = {
>   	.bios_param = megasas_bios_param,
>   	.use_clustering = ENABLE_CLUSTERING,
>   	.change_queue_depth = megasas_change_queue_depth,
> +	.change_queue_type = megasas_change_queue_type,
>   	.no_write_same = 1,
>   };
>   
> @@ -4909,6 +4937,10 @@ static int megasas_io_attach(struct megasas_instance *instance)
>   	host->this_id = instance->init_id;
>   	host->sg_tablesize = instance->max_num_sge;
>   
> +	if (!scsi_init_shared_tag_map(host, host->can_queue))
> +		printk(KERN_WARNING "megasas: enable TCQ support, depth %d",
> +			host->can_queue);
> +
>   	if (instance->fw_support_ieee)
>   		instance->max_sectors_per_req = MEGASAS_MAX_SECTORS_IEEE;
>