+ mm-damon-reclaim-validate-min_region_size-to-be-power-of-2.patch added to mm-new branch

+ mm-damon-reclaim-validate-min_region_size-to-be-power-of-2.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/reclaim: validate min_region_size to be power of 2
has been added to the -mm mm-new branch.  Its filename is
     mm-damon-reclaim-validate-min_region_size-to-be-power-of-2.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-reclaim-validate-min_region_size-to-be-power-of-2.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Liew Rui Yan <aethernet65535@gmail.com>
Subject: mm/damon/reclaim: validate min_region_size to be power of 2
Date: Fri, 1 May 2026 09:37:50 +0800

Problem
=======
When a user sets an invalid 'addr_unit' (e.g., 3) via DAMON_RECLAIM,
'min_region_sz' becomes a non-power-of-2 value. While damon_commit_ctx()
correctly detects this and returns -EINVAL, it sets the
'maybe_corrupted' flag during this process.

This flag causes the running kdamond to terminate. While the termination
is a safety measure, it is suboptimal in this case because the error is
just a simple invalid input from the user, which shouldn't neccessitate
stopping the kdamond.

Reproduction
============
1. Enable DAMON_RECLAIM
2. Set addr_unit=3
3. Commit inputs via 'commit_inputs'
4. Observe kdamond termination

Solution
========
Add an early validation in damon_reclaim_apply_parameters() to check
'min_region_sz' before any state change occurs. If it is non-power-of-2,
return -EINVAL immediately, preventing 'maybe_corrupted' from being set.

Link: https://lore.kernel.org/20260501013750.71704-3-aethernet65535@gmail.com
Signed-off-by: Liew Rui Yan <aethernet65535@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/reclaim.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/mm/damon/reclaim.c~mm-damon-reclaim-validate-min_region_size-to-be-power-of-2
+++ a/mm/damon/reclaim.c
@@ -210,6 +210,11 @@ static int damon_reclaim_apply_parameter
 	param_ctx->addr_unit = addr_unit;
 	param_ctx->min_region_sz = max(DAMON_MIN_REGION_SZ / addr_unit, 1);
 
+	if (!is_power_of_2(param_ctx->min_region_sz)) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	if (!damon_reclaim_mon_attrs.aggr_interval) {
 		err = -EINVAL;
 		goto out;
_

Patches currently in -mm which might be from aethernet65535@gmail.com are

mm-damon-ops-common-optimize-damon_hot_score-using-ilog2.patch
mm-damon-add-synchronous-commit-for-commit_inputs.patch
mm-damon-lru_sort-validate-min_region_size-to-be-power-of-2.patch
mm-damon-reclaim-validate-min_region_size-to-be-power-of-2.patch