[PATCH] scsi: core: Refine how we set tag_set NUMA node

[John Garry]

For SCSI hosts which enable host_tagset the NUMA node returned from
blk_mq_hw_queue_to_node() is NUMA_NO_NODE always. Then, since in
scsi_mq_setup_tags() the default we choose for the tag_set NUMA node is
NUMA_NO_NODE, we always evaluate the NUMA node as NUMA_NO_NODE in
functions like blk_mq_alloc_rq_map().

The reason we get NUMA_NO_NODE from blk_mq_hw_queue_to_node() is that
the hctx_idx passed is BLK_MQ_NO_HCTX_IDX - so we can't match against a
(HW) queue mapping index.

Improve this by defaulting the tag_set NUMA node to the same NUMA node
of the SCSI host DMA dev.

Signed-off-by: John Garry <john.garry@xxxxxxxxxx>

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index f69b77cbf538..8352f90d997d 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -229,10 +229,6 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	if (error)
 		goto fail;
 
-	error = scsi_mq_setup_tags(shost);
-	if (error)
-		goto fail;
-
 	if (!shost->shost_gendev.parent)
 		shost->shost_gendev.parent = dev ? dev : &platform_bus;
 	if (!dma_dev)
@@ -240,6 +236,10 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 
 	shost->dma_dev = dma_dev;
 
+	error = scsi_mq_setup_tags(shost);
+	if (error)
+		goto fail;
+
 	/*
 	 * Increase usage count temporarily here so that calling
 	 * scsi_autopm_put_host() will trigger runtime idle if there is
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0a70aa763a96..7faa83b89fa4 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1982,7 +1982,11 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 	tag_set->nr_maps = shost->nr_maps ? : 1;
 	tag_set->queue_depth = shost->can_queue;
 	tag_set->cmd_size = cmd_size;
+	#ifdef CONFIG_NUMA
+	tag_set->numa_node = shost->dma_dev->numa_node;
+	#else
 	tag_set->numa_node = NUMA_NO_NODE;
+	#endif
 	tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
 	tag_set->flags |=
 		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
-- 
2.26.2