Re: [PATCH V2 1/5] scsi: select reply queue from request's CPU

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On 27/05/2019 16:02, Ming Lei wrote:
Hisi_sas_v3_hw, hpsa, megaraid and mpt3sas use single blk-mq hw queue
to submit request, meantime apply multiple private reply queues served as
completion queue. The mapping between CPU and reply queue is setup via
pci_alloc_irq_vectors_affinity(PCI_IRQ_AFFINITY) just like the usual
blk-mq queue mapping.

These drivers always use current CPU(raw_smp_processor_id) to figure out
the reply queue. Switch to use request's CPU to get the reply queue,
so we can drain in-flight request via blk-mq's API before the last CPU of
the reply queue becomes offline.

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 drivers/scsi/hisi_sas/hisi_sas_main.c       |  5 +++--
 drivers/scsi/hpsa.c                         |  2 +-
 drivers/scsi/megaraid/megaraid_sas_fusion.c |  4 ++--
 drivers/scsi/mpt3sas/mpt3sas_base.c         | 16 ++++++++--------
 include/scsi/scsi_cmnd.h                    | 11 +++++++++++
 5 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index 8a7feb8ed8d6..ab9d8e7bfc8e 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -471,9 +471,10 @@ static int hisi_sas_task_prep(struct sas_task *task,
 		return -ECOMM;
 	}

+	/* only V3 hardware setup .reply_map */
 	if (hisi_hba->reply_map) {
-		int cpu = raw_smp_processor_id();
-		unsigned int dq_index = hisi_hba->reply_map[cpu];
+		unsigned int dq_index = hisi_hba->reply_map[
+			scsi_cmnd_cpu(task->uldd_task)];

Hi Ming,

There is a problem here. For ATA commands in libsas, task->uldd_task is ata_queued_cmd *, and not a scsi_cmnd *. It comes from https://elixir.bootlin.com/linux/v5.2-rc2/source/drivers/scsi/libsas/sas_ata.c#L212

Please see this later code, where we have this check:
	if (task->uldd_task) {
		struct ata_queued_cmd *qc;

		if (dev_is_sata(device)) {
			qc = task->uldd_task;
			scsi_cmnd = qc->scsicmd;
		} else {
			scsi_cmnd = task->uldd_task;
		}
	}
	rc  = hisi_sas_slot_index_alloc(hisi_hba, scsi_cmnd);

I suppose that we could solve by finding scsi_cmnd * earlier in hisi_sas_task_prep().


 		*dq_pointer = dq = &hisi_hba->dq[dq_index];
 	} else {
diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 1bef1da273c2..72f9edb86752 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -1145,7 +1145,7 @@ static void __enqueue_cmd_and_start_io(struct ctlr_info *h,

[snip]

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 76ed5e4acd38..ab60883c2c40 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -332,4 +332,15 @@ static inline unsigned scsi_transfer_length(struct scsi_cmnd *scmd)
 	return xfer_len;
 }

+static inline int scsi_cmnd_cpu(struct scsi_cmnd *scmd)
+{
+	if (!scmd || !scmd->request)
+		return raw_smp_processor_id();
+
+	if (!scmd->request->mq_ctx)
+		return raw_smp_processor_id();

nit: can we combine these tests? Or do you want a distinct check on scmd->request->mq_ctx, since blk_mq_rq_cpu() does not check it?

+
+	return blk_mq_rq_cpu(scmd->request);
+}
+
 #endif /* _SCSI_SCSI_CMND_H */

Thanks







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