[PATCH v6 08/10] scsi: ufshpb: Limit the number of inflight map requests

[Avri Altman <avri.altman@wdc.com>]

In host control mode the host is the originator of map requests. To not
flood the device with map requests, use a simple throttling mechanism
that limits the number of inflight map requests.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
---
 drivers/scsi/ufs/ufshpb.c | 11 +++++++++++
 drivers/scsi/ufs/ufshpb.h |  1 +
 2 files changed, 12 insertions(+)

diff --git a/drivers/scsi/ufs/ufshpb.c b/drivers/scsi/ufs/ufshpb.c
index 4639d3b5ddc0..f755f5a7775c 100644
--- a/drivers/scsi/ufs/ufshpb.c
+++ b/drivers/scsi/ufs/ufshpb.c
@@ -21,6 +21,7 @@
 #define READ_TO_MS 1000
 #define READ_TO_EXPIRIES 100
 #define POLLING_INTERVAL_MS 200
+#define THROTTLE_MAP_REQ_DEFAULT 1
 
 /* memory management */
 static struct kmem_cache *ufshpb_mctx_cache;
@@ -747,6 +748,14 @@ static struct ufshpb_req *ufshpb_get_map_req(struct ufshpb_lu *hpb,
 	struct ufshpb_req *map_req;
 	struct bio *bio;
 
+	if (hpb->is_hcm &&
+	    hpb->num_inflight_map_req >= THROTTLE_MAP_REQ_DEFAULT) {
+		dev_info(&hpb->sdev_ufs_lu->sdev_dev,
+			 "map_req throttle. inflight %d throttle %d",
+			 hpb->num_inflight_map_req, THROTTLE_MAP_REQ_DEFAULT);
+		return NULL;
+	}
+
 	map_req = ufshpb_get_req(hpb, srgn->rgn_idx, REQ_OP_SCSI_IN, false);
 	if (!map_req)
 		return NULL;
@@ -761,6 +770,7 @@ static struct ufshpb_req *ufshpb_get_map_req(struct ufshpb_lu *hpb,
 
 	map_req->rb.srgn_idx = srgn->srgn_idx;
 	map_req->rb.mctx = srgn->mctx;
+	hpb->num_inflight_map_req++;
 
 	return map_req;
 }
@@ -770,6 +780,7 @@ static void ufshpb_put_map_req(struct ufshpb_lu *hpb,
 {
 	bio_put(map_req->bio);
 	ufshpb_put_req(hpb, map_req);
+	hpb->num_inflight_map_req--;
 }
 
 static int ufshpb_clear_dirty_bitmap(struct ufshpb_lu *hpb,
diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
index c2821504a2d8..c9b8ee540704 100644
--- a/drivers/scsi/ufs/ufshpb.h
+++ b/drivers/scsi/ufs/ufshpb.h
@@ -213,6 +213,7 @@ struct ufshpb_lu {
 	struct ufshpb_req *pre_req;
 	int num_inflight_pre_req;
 	int throttle_pre_req;
+	int num_inflight_map_req;
 	struct list_head lh_pre_req_free;
 	int cur_read_id;
 	int pre_req_min_tr_len;
-- 
2.25.1