linux-kernel - Re: [PATCH v2 15/17] ibmvfc: send Cancel MAD down each hw scsi channel

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Message-ID: <21a7c970-2184-0524-5b42-1920eaa422a2@linux.vnet.ibm.com>
Date:   Wed, 2 Dec 2020 12:27:36 -0600
From:   Brian King <brking@...ux.vnet.ibm.com>
To:     Tyrel Datwyler <tyreld@...ux.ibm.com>,
        james.bottomley@...senpartnership.com
Cc:     martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        brking@...ux.ibm.com
Subject: Re: [PATCH v2 15/17] ibmvfc: send Cancel MAD down each hw scsi
 channel

On 12/1/20 6:53 PM, Tyrel Datwyler wrote:
> In general the client needs to send Cancel MADs and task management
> commands down the same channel as the command(s) intended to cancel or
> abort. The client assigns cancel keys per LUN and thus must send a
> Cancel down each channel commands were submitted for that LUN. Further,
> the client then must wait for those cancel completions prior to
> submitting a LUN RESET or ABORT TASK SET.
> 
> Allocate event pointers for each possible scsi channel and assign an
> event for each channel that requires a cancel. Wait for completion each
> submitted cancel.
> 
> Signed-off-by: Tyrel Datwyler <tyreld@...ux.ibm.com>
> ---
>  drivers/scsi/ibmvscsi/ibmvfc.c | 106 +++++++++++++++++++++------------
>  1 file changed, 68 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
> index 0b6284020f06..97e8eed04b01 100644
> --- a/drivers/scsi/ibmvscsi/ibmvfc.c
> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c
> @@ -2339,32 +2339,52 @@ static int ibmvfc_cancel_all(struct scsi_device *sdev, int type)
>  {
>  	struct ibmvfc_host *vhost = shost_priv(sdev->host);
>  	struct ibmvfc_event *evt, *found_evt;
> -	union ibmvfc_iu rsp;
> -	int rsp_rc = -EBUSY;
> +	struct ibmvfc_event **evt_list;
> +	union ibmvfc_iu *rsp;
> +	int rsp_rc = 0;
>  	unsigned long flags;
>  	u16 status;
> +	int num_hwq = 1;
> +	int i;
> +	int ret = 0;
>  
>  	ENTER;
>  	spin_lock_irqsave(vhost->host->host_lock, flags);
> -	found_evt = NULL;
> -	list_for_each_entry(evt, &vhost->sent, queue) {
> -		if (evt->cmnd && evt->cmnd->device == sdev) {
> -			found_evt = evt;
> -			break;
> +	if (vhost->using_channels && vhost->scsi_scrqs.active_queues)
> +		num_hwq = vhost->scsi_scrqs.active_queues;
> +
> +	evt_list = kcalloc(num_hwq, sizeof(*evt_list), GFP_KERNE> +	rsp = kcalloc(num_hwq, sizeof(*rsp), GFP_KERNEL);

Can't this just go on the stack? We don't want to be allocating memory
during error recovery. Or, alternatively, you could put this in the
vhost structure and protect it with a mutex. We only have enough events
to single thread these anyway.

> +
> +	for (i = 0; i < num_hwq; i++) {
> +		sdev_printk(KERN_INFO, sdev, "Cancelling outstanding commands on queue %d.\n", i);

Prior to this patch, if there was nothing outstanding to the device and cancel_all was called,
no messages would get printed. This is changing that behavior. Is that intentional? Additionally,
it looks like this will get a lot more vebose, logging a message for each hw queue, regardless
of whether there was anything outstanding. Perhaps you want to move this down to after the check
for !found_evt?

> +
> +		found_evt = NULL;
> +		list_for_each_entry(evt, &vhost->sent, queue) {
> +			if (evt->cmnd && evt->cmnd->device == sdev && evt->hwq == i) {
> +				found_evt = evt;
> +				break;
> +			}
>  		}
> -	}
>  



-- 
Brian King
Power Linux I/O
IBM Linux Technology Center