Re: [PATCH RFC v3 37/41] libsas: add tag to struct sas_task

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On 30/04/2020 14:19, Hannes Reinecke wrote:
All block layer commands now have a tag, so we should be storing
it in the sas_task structure for easier lookup.

This seems like a decent idea, to put the tag here, so that we don't need to do the lookup in the LLDD queuecommand.

However it feels safer to use a sas_task scsicmd->request->tag in the LLDD directly, if we can make that possible. More below.


Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
  drivers/scsi/libsas/sas_ata.c       | 4 ++++
  drivers/scsi/libsas/sas_init.c      | 2 ++
  drivers/scsi/libsas/sas_scsi_host.c | 2 +-
  include/scsi/libsas.h               | 2 ++
  4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index 5d716d388707..897007343b3d 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -211,6 +211,10 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
task->data_dir = qc->dma_dir;
  	task->scatter = qc->sg;
+	if (qc->scsicmd)
+		task->tag = qc->scsicmd->request->tag;
+	else
+		task->tag = qc->tag;

I think that this tag comes from ata_sas_allocate_tag(), and would be managed from yet another bitmap for ATA commands tags. Maybe we can allocate a sas slow task here, instead of using this tag. Needs more checking...

  	task->ata_task.retry_count = 1;
  	task->task_state_flags = SAS_TASK_STATE_PENDING;
  	qc->lldd_task = task;
diff --git a/drivers/scsi/libsas/sas_init.c b/drivers/scsi/libsas/sas_init.c
index 5aa8593b88b5..0d32cb49d0af 100644
--- a/drivers/scsi/libsas/sas_init.c
+++ b/drivers/scsi/libsas/sas_init.c
@@ -53,6 +53,7 @@ struct sas_task *sas_alloc_slow_task(struct sas_ha_struct *ha,
  	if (!slow)
  		goto out_err_slow;
+ task->tag = -1;
  	if (shost->nr_reserved_cmds) {
  		struct scsi_device *sdev;
@@ -66,6 +67,7 @@ struct sas_task *sas_alloc_slow_task(struct sas_ha_struct *ha,
  		slow->scmd = scsi_get_reserved_cmd(sdev, DMA_NONE, false);
  		if (!slow->scmd)
  			goto out_err_scmd;
+		task->tag = slow->scmd->request->tag;
  		ASSIGN_SAS_TASK(slow->scmd, task);
  	}
diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index c5a430e3fa2d..585e0df5fce2 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -149,7 +149,7 @@ static struct sas_task *sas_create_task(struct scsi_cmnd *cmd,
  	memcpy(task->ssp_task.LUN, &lun.scsi_lun, 8);
  	task->ssp_task.task_attr = TASK_ATTR_SIMPLE;
  	task->ssp_task.cmd = cmd;
-
+	task->tag = cmd->request->tag;
  	task->scatter = scsi_sglist(cmd);
  	task->num_scatter = scsi_sg_count(cmd);
  	task->total_xfer_len = scsi_bufflen(cmd);
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index c927228019c9..af864f68b5cc 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -594,6 +594,8 @@ struct sas_task {
  	u32    total_xfer_len;
  	u8     data_dir:2;	  /* Use PCI_DMA_... */
+ u32 tag;

unsigned, yet we assign it -1?

+
  	struct task_status_struct task_status;
  	void   (*task_done)(struct sas_task *);

Thanks!



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