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Thu, 03 Sep 2026 01:45:54 -0700 (PDT) From: Kunwu Chan X-Google-Original-From: Kunwu Chan To: SJ Park Cc: Kunwu Chan , Andrew Morton , stable@vger.kernel.org, Ravi Jonnalagadda , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Kunwu Chan Subject: Re: [PATCH 3/4] mm/damon/core: copy nid for eligible_mem_bp damos quota goal commit Date: Thu, 3 Sep 2026 16:45:45 +0800 Message-ID: <20260903084547.960584-1-kunwu.chan@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260902002725.108635-4-sj@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 1 Sep 2026 17:27:22 -0700 SJ Park wrote: > damos_commit_quota_goal_union() is not updating the ->nid union field > when the goal metric is DAMOS_QUITA_NODE_ELIGIBLE_MEM_BP. Hence, if a > DAMOS quota goal of the type is online committed in a way that it will > reuse other quota goal's memory space, the new goal will work with a > garbage nid value. As a result, the DAMOS scheme can show unexpected > aggressiveness. Do the update. > > The user impact is not catastrophic. No leak or crash happens. Doing > the quota goal online commit that can reproduce the issue is expected to > be not common. This issue was not found by real users but the AI > review. That said, the issue can reliably be reproduced. > > This issue was discovered [1] by Sashiko. > > [1] https://lore.kkernel.org/20260827045035.94611-1-sj@kernel.org Hi SJ, The fix is consistent with the other node-based quota metrics. I also checked that damos_get_node_eligible_mem_bp() directly uses goal->nid when calculating the current value. One minor typo: the [1] has an extra k (kkernel should be kernel). Reviewed-by: Kunwu Chan Thanks, Kunwu > > Fixes: 9138e27a3bc3 ("mm/damon: add node_eligible_mem_bp goal metric") > Cc: # 7.2.x > Signed-off-by: SJ Park > --- > mm/damon/core.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 20748b0a71026..53c3f97e3f126 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -1143,6 +1143,9 @@ static void damos_commit_quota_goal_union( > dst->nid = src->nid; > dst->memcg_id = src->memcg_id; > break; > + case DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP: > + dst->nid = src->nid; > + break; > default: > break; > } > -- > 2.47.3 > Sent using hkml (https://github.com/sjp38/hackermail)