[PATCH 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 from 429497
bytes on, and wraps to exactly zero at the 1 GiB that
Documentation/admin-guide/mm/damon/usage.rst uses as its example, since
1 GiB * 10000 is 2500 * 2^32.  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 saturates the conversion.  Patch 2 pins the boundary in the core
kunit suite, where it fails without patch 1 on any word size.

DAMON kunit: 36 tests, all passing with both patches; 35 passing and
damos_test_esz_goal_temporal failing with patch 2 alone.  The DAMON
selftests do not reach the changed function: a build with a print at its
entry stayed silent through all fifteen of them and fired as soon as a
scheme was configured with the temporal tuner.

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             |  6 +++---
 mm/damon/tests/core-kunit.h | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 3 deletions(-)


base-commit: 498ee28e5ec4727f829507c4a1bde3ab1b7704cd
-- 
2.53.0