Re: [PATCH] libsas: don't treat underrun as an error on SMP tasks

[FUJITA Tomonori <tomof@acm.org>]

On Sat, 29 Dec 2007 11:49:53 -0600
James Bottomley <James.Bottomley@HansenPartnership.com> wrote:

> All SMP tasks sent through bsg generate messages like:
> 
> sas: smp_execute_task: task to dev 500605b000001450 response: 0x0 status 0x81
> 
> Three times (because the task gets retried).  Firstly, don't retry
> either overrun or underrun (the data buffer isn't going to change size)
> and secondly, just report the underrun but don't set an error for it.
> This is necessary so bsg can report back the residual.
> 
> James
> 
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 76555b1..1578059 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -109,6 +109,16 @@ static int smp_execute_task(struct domain_device *dev, void *req, int req_size,
>  		    task->task_status.stat == SAM_GOOD) {
>  			res = 0;
>  			break;
> +		} if (task->task_status.resp == SAS_TASK_COMPLETE &&
> +		      task->task_status.stat == SAS_DATA_UNDERRUN) {
> +			/* no error, but return the number of bytes of
> +			 * underrun */
> +			res = task->task_status.residual;
> +			break;
> +		} if (task->task_status.resp == SAS_TASK_COMPLETE &&
> +		      task->task_status.stat == SAS_DATA_OVERRUN) {
> +			res = -EMSGSIZE;
> +			break;
>  		} else {
>  			SAS_DPRINTK("%s: task to dev %016llx response: 0x%x "
>  				    "status 0x%x\n", __FUNCTION__,
> @@ -1924,6 +1934,11 @@ int sas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
>  
>  	ret = smp_execute_task(dev, bio_data(req->bio), req->data_len,
>  			       bio_data(rsp->bio), rsp->data_len);
> +	if (ret > 0) {
> +		/* positive number is the untransferred residual */
> +		rsp->data_len = ret;
> +		ret = 0;
> +	}

Would be better to update dout_resid too (on sucess, we can set
req->data_len to zero, I think)?

Here's a patch to do the same thing for mpt sas, an updated version
of:

http://marc.info/?l=linux-scsi&m=119811872823947&w=2

--
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Subject: [PATCH] mpt fusion: mptsas_smp_handler updates resid

This patch fixes mptsas_smp_handler to update both din_resid or
dout_resid on success. bsg can report back the residual.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
 drivers/message/fusion/mptsas.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c
index e4c94f9..f77b329 100644
--- a/drivers/message/fusion/mptsas.c
+++ b/drivers/message/fusion/mptsas.c
@@ -1343,6 +1343,8 @@ static int mptsas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 		smprep = (SmpPassthroughReply_t *)ioc->sas_mgmt.reply;
 		memcpy(req->sense, smprep, sizeof(*smprep));
 		req->sense_len = sizeof(*smprep);
+		req->data_len = 0;
+		rsp->data_len -= smprep->ResponseDataLength;
 	} else {
 		printk(MYIOC_s_ERR_FMT "%s: smp passthru reply failed to be returned\n",
 		    ioc->name, __FUNCTION__);
-- 
1.5.3.4