Re: [PATCH 6/9] scsi: hpsa: convert private reply queue to blk-mq hw queue

From: Hannes Reinecke <hare@suse.de>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>,
	John Garry <john.garry@huawei.com>,
	Don Brace <don.brace@microsemi.com>,
	Kashyap Desai <kashyap.desai@broadcom.com>,
	Sathya Prakash <sathya.prakash@broadcom.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 6/9] scsi: hpsa: convert private reply queue to blk-mq hw queue
Date: Fri, 31 May 2019 08:15:23 +0200	[thread overview]
Message-ID: <d489e4e8-e625-4c68-4ab8-9b70e5989cc8@suse.de> (raw)
In-Reply-To: <20190531022801.10003-7-ming.lei@redhat.com>

On 5/31/19 4:27 AM, Ming Lei wrote:
> SCSI's reply qeueue is very similar with blk-mq's hw queue, both
> assigned by IRQ vector, so map te private reply queue into blk-mq's hw
> queue via .host_tagset.
> 
> Then the private reply mapping can be removed.
> 
> Another benefit is that the request/irq lost issue may be solved in
> generic approach because managed IRQ may be shutdown during CPU
> hotplug.
> 
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/scsi/hpsa.c | 49 ++++++++++++++++++---------------------------
>  1 file changed, 19 insertions(+), 30 deletions(-)
> 
There had been requests to make the internal interrupt mapping optional;
but I guess we first should
> diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
> index 1bef1da273c2..c7136f9f0ce1 100644
> --- a/drivers/scsi/hpsa.c
> +++ b/drivers/scsi/hpsa.c
> @@ -51,6 +51,7 @@
>  #include <linux/jiffies.h>
>  #include <linux/percpu-defs.h>
>  #include <linux/percpu.h>
> +#include <linux/blk-mq-pci.h>
>  #include <asm/unaligned.h>
>  #include <asm/div64.h>
>  #include "hpsa_cmd.h"
> @@ -902,6 +903,18 @@ static ssize_t host_show_legacy_board(struct device *dev,
>  	return snprintf(buf, 20, "%d\n", h->legacy_board ? 1 : 0);
>  }
>  
> +static int hpsa_map_queues(struct Scsi_Host *shost)
> +{
> +	struct ctlr_info *h = shost_to_hba(shost);
> +	struct blk_mq_queue_map *qmap = &shost->tag_set.map[HCTX_TYPE_DEFAULT];
> +
> +	/* Switch to cpu mapping in case that managed IRQ isn't used */
> +	if (shost->nr_hw_queues > 1)
> +		return blk_mq_pci_map_queues(qmap, h->pdev, 0);
> +	else
> +		return blk_mq_map_queues(qmap);
> +}
> +
>  static DEVICE_ATTR_RO(raid_level);
>  static DEVICE_ATTR_RO(lunid);
>  static DEVICE_ATTR_RO(unique_id);
This helper is pretty much shared between all converted drivers.
Shouldn't we have a common function here?
Something like

scsi_mq_host_tag_map(struct Scsi_Host *shost, int offset)?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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