Re: [PATCH V2 3/6] scsi: add flag of .use_managed_irq to 'struct Scsi_Host'

[John Garry <john.garry@huawei.com>]

On 02/07/2021 16:05, Ming Lei wrote:
> blk-mq needs this information of using managed irq for improving
> deactivating hctx, so add such flag to 'struct Scsi_Host', then
> drivers can pass such flag to blk-mq via scsi_mq_setup_tags().
> 
> The rule is that driver has to tell blk-mq if managed irq is used.
> 
> Signed-off-by: Ming Lei<ming.lei@redhat.com>

As was said before, can we have something like this instead of relying 
on the LLDs to do the setting:

--------->8------------

diff --git a/block/blk-mq-pci.c b/block/blk-mq-pci.c
index b595a94c4d16..2037a5b69fe1 100644
--- a/block/blk-mq-pci.c
+++ b/block/blk-mq-pci.c
@@ -37,7 +37,7 @@ int blk_mq_pci_map_queues(struct blk_mq_queue_map 
*qmap, struct pci_dev *pdev,
  		for_each_cpu(cpu, mask)
  			qmap->mq_map[cpu] = qmap->queue_offset + queue;
  	}
-
+	qmap->drain_hwq = 1;
  	return 0;

  fallback:
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 46fe5b45a8b8..7b610e680e08 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3408,7 +3408,8 @@ static int blk_mq_update_queue_map(struct 
blk_mq_tag_set *set)
  		set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;

  	if (set->ops->map_queues && !is_kdump_kernel()) {
-		int i;
+		struct blk_mq_queue_map *qmap = &set->map[HCTX_TYPE_DEFAULT];
+		int i, ret;

  		/*
  		 * transport .map_queues is usually done in the following
@@ -3427,7 +3428,12 @@ static int blk_mq_update_queue_map(struct 
blk_mq_tag_set *set)
  		for (i = 0; i < set->nr_maps; i++)
  			blk_mq_clear_mq_map(&set->map[i]);

-		return set->ops->map_queues(set);
+		ret = set->ops->map_queues(set);
+		if (ret)
+			return ret;
+		if (qmap->drain_hwq)
+			set->flags |= BLK_MQ_F_MANAGED_IRQ;
+		return 0;
  	} else {
  		BUG_ON(set->nr_maps > 1);
  		return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 65ed99b3f2f0..2b2e71ff43e0 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -193,6 +193,7 @@ struct blk_mq_queue_map {
  	unsigned int *mq_map;
  	unsigned int nr_queues;
  	unsigned int queue_offset;
+	bool drain_hwq;
  };