Re: [PATCH v2 6/7] SRP transport: Port srp_wait_for_queuecommand() to scsi-mq

[Christoph Hellwig]

On Wed, Oct 05, 2016 at 02:51:50PM -0700, Bart Van Assche wrote:
> There are multiple direct blk_*() calls in other SCSI transport drivers. So 
> my proposal is to wait with moving this code into scsi_lib.c until there is 
> a second user of this code.

I still don't think these low-level difference for blk-mq vs legacy
request belong into a scsi LLDD.  So I concur with Sagi that this
should go into the core SCSI code.

In fact I suspect we should just call it directly from
scsi_internal_device_block, and maybe even scsi_internal_device_unblock
for case of setting the device offline.
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Re: [PATCH v2 6/7] SRP transport: Port srp_wait_for_queuecommand() to scsi-mq

[Sagi Grimberg]

+static void srp_mq_wait_for_queuecommand(struct Scsi_Host *shost)
+{
+   struct scsi_device *sdev;
+   struct request_queue *q;
+
+   shost_for_each_device(sdev, shost) {
+   q = sdev->request_queue;
+
+   blk_mq_quiesce_queue(q);
+   blk_mq_resume_queue(q);
+   }
+}
+


This *should* live in scsi_lib.c. I suspect that
various drivers would really want this functionality.

Thoughts?
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Re: [PATCH v2 6/7] SRP transport: Port srp_wait_for_queuecommand() to scsi-mq

[Hannes Reinecke]

On 09/29/2016 02:01 AM, Bart Van Assche wrote:
> Ensure that if scsi-mq is enabled that srp_wait_for_queuecommand()
> waits until ongoing shost->hostt->queuecommand() calls have finished.
> 
> Signed-off-by: Bart Van Assche 
> Cc: James Bottomley 
> Cc: Martin K. Petersen 
> Cc: Doug Ledford 
> ---
>  drivers/scsi/scsi_transport_srp.c | 24 
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
Reviewed-by: Hannes Reinecke 

Cheers,

Hannes
-- 
Dr. Hannes Reinecke   zSeries & Storage
h...@suse.de  +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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[PATCH v2 6/7] SRP transport: Port srp_wait_for_queuecommand() to scsi-mq

[Bart Van Assche]

Ensure that if scsi-mq is enabled that srp_wait_for_queuecommand()
waits until ongoing shost->hostt->queuecommand() calls have finished.

Signed-off-by: Bart Van Assche 
Cc: James Bottomley 
Cc: Martin K. Petersen 
Cc: Doug Ledford 
---
 drivers/scsi/scsi_transport_srp.c | 24 
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_transport_srp.c 
b/drivers/scsi/scsi_transport_srp.c
index e3cd3ec..f1d580e 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -25,6 +25,7 @@
 #include 
 #include 
 #include 
+#include 
 
 #include 
 #include 
@@ -405,8 +406,6 @@ static void srp_reconnect_work(struct work_struct *work)
 /**
  * scsi_request_fn_active() - number of kernel threads inside scsi_request_fn()
  * @shost: SCSI host for which to count the number of scsi_request_fn() 
callers.
- *
- * To do: add support for scsi-mq in this function.
  */
 static int scsi_request_fn_active(struct Scsi_Host *shost)
 {
@@ -425,11 +424,28 @@ static int scsi_request_fn_active(struct Scsi_Host *shost)
return request_fn_active;
 }
 
+static void srp_mq_wait_for_queuecommand(struct Scsi_Host *shost)
+{
+   struct scsi_device *sdev;
+   struct request_queue *q;
+
+   shost_for_each_device(sdev, shost) {
+   q = sdev->request_queue;
+
+   blk_mq_quiesce_queue(q);
+   blk_mq_resume_queue(q);
+   }
+}
+
 /* Wait until ongoing shost->hostt->queuecommand() calls have finished. */
 static void srp_wait_for_queuecommand(struct Scsi_Host *shost)
 {
-   while (scsi_request_fn_active(shost))
-   msleep(20);
+   if (shost->use_blk_mq) {
+   srp_mq_wait_for_queuecommand(shost);
+   } else {
+   while (scsi_request_fn_active(shost))
+   msleep(20);
+   }
 }
 
 static void __rport_fail_io_fast(struct srp_rport *rport)
-- 
2.10.0

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