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t=1793854517; bh=MqA1v6U9I7VtulcS+AOn9l6cfVQac8Bgf0Fd+CPq7D8=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=U9KjKHYkLFtNg94b3bFsLOzRkcieNXJ3km+2Uh5pRlyHHDi2BjkqzuEkf8uf60GJp puJntGXpoVnSTV749phc6j/wSpVuJdY2ZnKuTSmD7Kojj0MbSG7hH2OZNiLNa2jorM QGALskc4xjgWvHs5MQT6YZt2miKq8DiCus4KxMkeqBuDQAbj1hdv0fTJLdkGa+INRM 5dBrimHzj9+jHg3ZcssZPZIYCH6juuk708yjwPIMx6mHsl9BuF23J9W48o2EM98MiN 3nRu9wBMjMIJC+KEBtuj/gxbJeR6mDSfd9GfjRrjIJ3JWSKLfDE7EalA1ZQeawP6mC a6Lkrc/UlbXrg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [RFC PATCH v2 1/4] mm/damon/core: add DAMOS_FILTER_TYPE_AGE_MS Reply-To: sashiko-reviews@lists.linux.dev To: "SJ Park" Cc: "Andrew Morton" , damon@lists.linux.dev, linux-mm@kvack.org In-Reply-To: <20261105044425.87142-2-sj@kernel.org> References: <20261105044425.87142-1-sj@kernel.org> <20261105044425.87142-2-sj@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 05 Nov 2026 04:55:17 +0000 X-Stat-Signature: 1ea4tzgb5un45e8ez4xwm5krbzq9ggp5 X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E3FB91C0006 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793854518-262947 X-HE-Meta: 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 pr3U9yEi 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [Medium] mm/damon: 64-to-32-bit truncation of age_ms in damos_filter_matc= h() -- commit 2459402d4dc794f740b6a5720a69fe4a1a61ae62 Author: SJ Park mm/damon/core: add DAMOS_FILTER_TYPE_AGE_MS This commit introduces DAMOS_FILTER_TYPE_AGE_MS in the DAMON API and core layer to allow filtering DAMOS target regions by age in milliseconds. It converts the region age from aggregation intervals to milliseconds using div_u64() and compares the result against damos_filter->range_{min,max}. > diff --git a/mm/damon/core.c b/mm/damon/core.c > index d36823f4d0928..0a056949604f9 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c [ ... ] > @@ -2552,7 +2554,7 @@ static bool damos_filter_match(struct damon_ctx *ct= x, struct damon_target *t, > bool matched =3D false; > struct damon_target *ti; > int target_idx =3D 0; > - unsigned long start, end, wsum; > + unsigned long start, end, wsum, age_ms; > =20 > *err =3D 0; > switch (filter->type) { > @@ -2594,6 +2596,12 @@ static bool damos_filter_match(struct damon_ctx *c= tx, struct damon_target *t, > matched =3D filter->range_min <=3D wsum && > wsum <=3D filter->range_max; > break; > + case DAMOS_FILTER_TYPE_AGE_MS: > + age_ms =3D div_u64((u64)r->age * ctx->attrs.aggr_interval, > + USEC_PER_MSEC); > + matched =3D filter->range_min <=3D age_ms && > + age_ms <=3D filter->range_max; > + break; [Severity: Medium] In damos_filter_match(), age_ms is declared as unsigned long. On 32-bit architectures, unsigned long is 32 bits wide, so storing the u64 return val= ue of div_u64() into age_ms truncates the upper 32 bits whenever the region age in milliseconds exceeds ULONG_MAX (about 49.7 days, or for example r->age >=3D 42,949,673 at the default 100,000 us aggr_interval, and proportionally earlier when aggr_interval is larger). When that happens during kdamond_apply_schemes() -> damon_do_apply_schemes() -> damos_apply_scheme() -> damos_filter_out() -> damos_core_filter_out() -> damos_filter_match(), age_ms wraps modulo 2^32 and can misclassify old regions as young regions or fail to match old-region filters. By comparison, damon_hot_score() in mm/damon/ops-common.c stores the result of div_u64() in a u64 variable (as fixed in commit 0284dff76e87 ("mm/damon/ ops-common: fix 64-bit division in damon_hot_score()")): mm/damon/ops-common.c:damon_hot_score() { ... u64 age_in_sec; ... age_in_sec =3D div_u64((u64)r->age * c->attrs.aggr_interval, USEC_PER_SEC); ... } Should age_ms be declared as u64 (or saturated to ULONG_MAX before storing = into age_ms so filters with range_max =3D=3D ULONG_MAX on 32-bit continue to mat= ch) to avoid truncating the quotient on 32-bit systems? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261105044425.8714= 2-1-sj@kernel.org?part=3D1