[PATCH v3 0/2] mm/damon: fix the temporal goal tuner's size quota conversion

[Donggeun Yoo <donggeunyoo.kernel@gmail.com>]

damos_goal_tune_esz_bp_temporal() hands the size quota to
damos_set_effective_quota() through quota->esz_bp in basis points, and
the multiply that gets it there is unchecked.  On 32-bit it wraps above
429496 bytes, and to exactly zero for every multiple of 256 MiB.  A zero
effective quota makes damos_quota_is_full() true on the first test of
every charge window, so the scheme applies nothing for as long as the
goal is unachieved.

Patch 1 bounds the conversion.  Patch 2 pins the boundary in the core
kunit suite, where it would fail without patch 1 on any word size.

v2: https://lore.kernel.org/damon/20260920023111.2466265-1-donggeunyoo.kernel@gmail.com/

Changes in v3, all from SJ Park's review; the code is unchanged:
- patch 1: wrap the changelog at 72 columns, say what the impact is and
  is not, fold the 64-bit boundary into the trigger conditions rather
  than arguing it separately, and drop the passage on why widening
  esz_bp is not the fix
- patch 2: wrap the changelog at 72 columns; pick up the Reviewed-by
- drop the documentation patch, which SJ asked to drop

Rebased onto mm-new 87acb5b914c2; v2's base is no longer in that branch.

DAMON kunit on x86_64, on the new base: 36 tests, all passing with both
patches; 35 passing and damos_test_esz_goal_temporal failing with patch
2 alone.

Donggeun Yoo (2):
  mm/damon/core: prevent size quota overflow in the temporal goal tuner
  mm/damon/tests/core-kunit: test the temporal tuner's size quota
    conversion

 mm/damon/core.c             |  2 +-
 mm/damon/tests/core-kunit.h | 48 +++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

-- 
2.53.0