From 9bd8b264ec3cdd8de86753051d2ff2a311c506f2 Mon Sep 17 00:00:00 2001
From: Kozlowski Mateusz <mateusz.kozlowski@intel.com>
Date: Tue, 10 Jan 2023 11:57:25 +0100
Subject: [PATCH] lib/ftl: Update GC band selection mechanism

Don't let the invalidity value continuously drop in degenerate scenarios -
previously could have happened if band_cmp picked based on other value, when invalidity is similar.

Signed-off-by: Kozlowski Mateusz <mateusz.kozlowski@intel.com>
Signed-off-by: Mariusz Barczak <mariusz.barczak@intel.com>
Change-Id: I33166501e832cd7f359b3acef1e614cf9b1288d5
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/16215
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <smatsumoto@nvidia.com>
---
 lib/ftl/ftl_band.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/ftl/ftl_band.c b/lib/ftl/ftl_band.c
index ac1898afd..b5a2dd6ee 100644
--- a/lib/ftl/ftl_band.c
+++ b/lib/ftl/ftl_band.c
@@ -610,9 +610,12 @@ ftl_band_search_next_to_reloc(struct spdk_ftl_dev *dev)
 			if (phys_id == FTL_BAND_PHYS_ID_INVALID ||
 			    band_cmp(invalidity, wr_cnt, max_invalidity, max_wr_cnt,
 				     band->phys_id, phys_id)) {
-				max_invalidity = invalidity;
 				max_wr_cnt = wr_cnt;
 				phys_id = band->phys_id;
+
+				if (invalidity > max_invalidity) {
+					max_invalidity = invalidity;
+				}
 			}
 		}
 	}