linux-kernel - [PATCH v12 05/12] scsi: ufshpb: Make eviction depends on region's reads

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Message-Id: <20210712095039.8093-6-avri.altman@wdc.com>
Date:   Mon, 12 Jul 2021 12:50:32 +0300
From:   Avri Altman <avri.altman@....com>
To:     "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, Bart Van Assche <bvanassche@....org>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Daejun Park <daejun7.park@...sung.com>,
        alim.akhtar@...sung.com, asutoshd@...eaurora.org,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <avi.shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>, cang@...eaurora.org,
        stanley.chu@...iatek.com, Avri Altman <avri.altman@....com>
Subject: [PATCH v12 05/12] scsi: ufshpb: Make eviction depends on region's reads

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@....com>
Reviewed-by: Daejun Park <daejun7.park@...sung.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 d46235527fba..1eadfc12b6a7 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;
@@ -1056,6 +1057,13 @@ 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;
 	}
@@ -1223,7 +1231,7 @@ 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;
@@ -1250,7 +1258,15 @@ 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