+ mm-damon-core-reset-watermark-wait-state-on-each-iteration.patch added to mm-hotfixes-unstable branch

+ mm-damon-core-reset-watermark-wait-state-on-each-iteration.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/core: reset watermark wait state on each iteration
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-damon-core-reset-watermark-wait-state-on-each-iteration.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-reset-watermark-wait-state-on-each-iteration.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Aveline Noir <jm5905938@gmail.com>
Subject: mm/damon/core: reset watermark wait state on each iteration
Date: Mon, 02 Nov 2026 06:46:24 -0800

Patch series "mm/damon: fix watermark state, kunit pid leak and selftest
fake pass".

Three hotfixes for core, kunit and selftest.  Fix kdamond deactivation
from missed watermark reset with patch 1.  Fix pid leak in kunit test
with patch 2.  Fix a selftest wrongly passing when it should skip, with
patch 3.

Note for reviewers.  This series is a collection of fixes that were
initially developed by different people.  Changelog is in each patch.


This patch (of 3):

Found while reviewing the DAMON source code that if an online commit
removes all schemes while kdamond is waiting for watermark activation,
the scheme loop becomes empty but min_wait_time keeps the previous
positive value.  kdamond then keeps sleeping instead of resuming
monitoring without schemes.

The way to wake up the kdamond again without DAMON is bit complicated.
Install a scheme having watermarks that can activate the kdamond again,
and remove the scheme again.  Doable but cumbersome and complicated.

Initialize min_wait_time and init_wait_time on each loop iteration so
the wait is calculated from the current schemes and an empty scheme
list resumes monitoring.

Link: https://lore.kernel.org/20261102144627.88843-1-sj@kernel.org
Link: https://lore.kernel.org/20261102144627.88843-2-sj@kernel.org
Fixes: da87878010e5 ("mm/damon/sysfs: support online inputs update")
Signed-off-by: Aveline Noir <jm5905938@gmail.com>
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: Wang Xiaolei <xiaoleiwangxiaolei@gmail.com>
Cc: <stable@vger.kernel.org> # 5.19.x
---

 mm/damon/core.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-reset-watermark-wait-state-on-each-iteration
+++ a/mm/damon/core.c
@@ -3976,10 +3976,11 @@ static int kdamond_wait_activation(struc
 {
 	struct damos *s;
 	unsigned long wait_time;
-	unsigned long min_wait_time = 0;
-	bool init_wait_time = false;
 
 	while (!kdamond_need_stop(ctx)) {
+		unsigned long min_wait_time = 0;
+		bool init_wait_time = false;
+
 		damon_for_each_scheme(s, ctx) {
 			wait_time = damos_wmark_wait_us(s);
 			if (!init_wait_time || wait_time < min_wait_time) {
_

Patches currently in -mm which might be from jm5905938@gmail.com are

mm-damon-core-reset-watermark-wait-state-on-each-iteration.patch
mm-damon-ops-common-align-mmu-notifier-range-when-clearing-pmd-young-bit.patch
mm-damon-stat-avoid-32-bit-overflow-in-idle-percentiles.patch
mm-damon-pvaddr-skip-folios-already-on-the-migration-target-node.patch