From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Liew Rui Yan <aethernet65535@gmail.com>,
	SJ Park <sj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12.y 2/2] mm/damon/core: allow esz to be set to zero
Date: Tue, 29 Sep 2026 20:04:01 -0400
Message-ID: <20260930000401.2861657-2-sashal@kernel.org>
In-Reply-To: <20260930000401.2861657-1-sashal@kernel.org>
References: <2026092900-prize-superglue-6d70@gregkh>
 <20260930000401.2861657-1-sashal@kernel.org>
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From: Liew Rui Yan <aethernet65535@gmail.com>

[ Upstream commit 90179da203ba8b708c84a12a07cd44be0f346334 ]

When the temporal quota goal tuner determines that the goal has been
achieved (score >= 10000), it sets esz_bp to zero so that the esz becomes
zero.  However, damos_set_effective_quota() clamps the esz to
min_region_sz when quota->ms is set.

This is a minor issue, the main problem is that it doesn't match the
description in the documentation, which state that if the goal has already
been [over-]achieved, the quota will be set to zero.

Fix this by set quota (esz) as minimum as possible.

Link: https://lore.kernel.org/20260908135413.97570-1-sj@kernel.org
Fixes: 8bbde987c2b8 ("mm/damon/core: disallow time-quota setting zero esz")
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Liew Rui Yan <aethernet65535@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # v7.1.x
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/damon/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index c74a0cc9ea413..5b86d3db627ad 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1638,6 +1638,7 @@ static void damos_set_effective_quota(struct damon_ctx *ctx, struct damos *s)
 	struct damos_quota *quota = &s->quota;
 	unsigned long throughput;
 	unsigned long esz = ULONG_MAX;
+	unsigned long esz_time;
 
 	if (!quota->ms && list_empty(&quota->goals)) {
 		quota->esz = quota->sz;
@@ -1659,8 +1660,8 @@ static void damos_set_effective_quota(struct damon_ctx *ctx, struct damos *s)
 					1000000, quota->total_charged_ns);
 		else
 			throughput = PAGE_SIZE * 1024;
-		esz = min(throughput * quota->ms, esz);
-		esz = max(ctx->min_region_sz, esz);
+		esz_time = max(throughput * quota->ms, ctx->min_region_sz);
+		esz = min(esz_time, esz);
 	}
 
 	if (quota->sz && quota->sz < esz)
-- 
2.53.0