linux-kernel - Re: [PATCH v8 13/18] scsi: core: Show nr_hw

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Date:   Thu, 10 Sep 2020 09:33:07 +0100
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <don.brace@...rosemi.com>,
        <kashyap.desai@...adcom.com>, <ming.lei@...hat.com>,
        <bvanassche@....org>, <dgilbert@...erlog.com>,
        <paolo.valente@...aro.org>, <hare@...e.de>, <hch@....de>
CC:     <sumit.saxena@...adcom.com>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <esc.storagedev@...rosemi.com>, <megaraidlinux.pdl@...adcom.com>,
        <chenxiang66@...ilicon.com>, <luojiaxing@...wei.com>
Subject: Re: [PATCH v8 13/18] scsi: core: Show nr_hw_queues in sysfs

On 19/08/2020 16:20, John Garry wrote:
> So that we don't use a value of 0 for when Scsi_Host.nr_hw_queues is unset,
> use the tag_set->nr_hw_queues (which holds 1 for this case).
> 
> Signed-off-by: John Garry <john.garry@...wei.com>

Note that there has been no review on this patch yet.

It's not strictly necessary, but I see it as useful. The same info can 
be derived indirectly from block debugfs, but that's not always 
available (debugfs, that is).

Thanks,
john

> ---
>   drivers/scsi/scsi_sysfs.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 163dbcb741c1..d6e344fa33ad 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -393,6 +393,16 @@ show_use_blk_mq(struct device *dev, struct device_attribute *attr, char *buf)
>   }
>   static DEVICE_ATTR(use_blk_mq, S_IRUGO, show_use_blk_mq, NULL);
>   
> +static ssize_t
> +show_nr_hw_queues(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct Scsi_Host *shost = class_to_shost(dev);
> +	struct blk_mq_tag_set *tag_set = &shost->tag_set;
> +
> +	return snprintf(buf, 20, "%d\n", tag_set->nr_hw_queues);
> +}
> +static DEVICE_ATTR(nr_hw_queues, S_IRUGO, show_nr_hw_queues, NULL);
> +
>   static struct attribute *scsi_sysfs_shost_attrs[] = {
>   	&dev_attr_use_blk_mq.attr,
>   	&dev_attr_unique_id.attr,
> @@ -411,6 +421,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
>   	&dev_attr_prot_guard_type.attr,
>   	&dev_attr_host_reset.attr,
>   	&dev_attr_eh_deadline.attr,
> +	&dev_attr_nr_hw_queues.attr,
>   	NULL
>   };
>   
>