[PATCH v6 04/10] scsi: ufshpb: Make eviction depends on region's reads

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

In host mode, eviction is considered an extreme measure.
verify that the entering region has enough reads, and the exiting
region has much less reads.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
---
 drivers/scsi/ufs/ufshpb.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshpb.c b/drivers/scsi/ufs/ufshpb.c
index a1519cbb4ce0..5e757220d66a 100644
--- a/drivers/scsi/ufs/ufshpb.c
+++ b/drivers/scsi/ufs/ufshpb.c
@@ -17,6 +17,7 @@
 #include "../sd.h"
 
 #define ACTIVATION_THRESHOLD 8 /* 8 IOs */
+#define EVICTION_THRESHOLD (ACTIVATION_THRESHOLD << 5) /* 256 IOs */
 
 /* memory management */
 static struct kmem_cache *ufshpb_mctx_cache;
@@ -1047,6 +1048,13 @@ static struct ufshpb_region *ufshpb_victim_lru_info(struct ufshpb_lu *hpb)
 		if (ufshpb_check_srgns_issue_state(hpb, rgn))
 			continue;
 
+		/*
+		 * in host control mode, verify that the exiting region
+		 * has less reads
+		 */
+		if (hpb->is_hcm && rgn->reads > (EVICTION_THRESHOLD >> 1))
+			continue;
+
 		victim_rgn = rgn;
 		break;
 	}
@@ -1219,7 +1227,7 @@ static int ufshpb_issue_map_req(struct ufshpb_lu *hpb,
 
 static int ufshpb_add_region(struct ufshpb_lu *hpb, struct ufshpb_region *rgn)
 {
-	struct ufshpb_region *victim_rgn;
+	struct ufshpb_region *victim_rgn = NULL;
 	struct victim_select_info *lru_info = &hpb->lru_info;
 	unsigned long flags;
 	int ret = 0;
@@ -1246,7 +1254,15 @@ static int ufshpb_add_region(struct ufshpb_lu *hpb, struct ufshpb_region *rgn)
 			 * It is okay to evict the least recently used region,
 			 * because the device could detect this region
 			 * by not issuing HPB_READ
+			 *
+			 * in host control mode, verify that the entering
+			 * region has enough reads
 			 */
+			if (hpb->is_hcm && rgn->reads < EVICTION_THRESHOLD) {
+				ret = -EACCES;
+				goto out;
+			}
+
 			victim_rgn = ufshpb_victim_lru_info(hpb);
 			if (!victim_rgn) {
 				dev_warn(&hpb->sdev_ufs_lu->sdev_dev,
-- 
2.25.1