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bh=WiXFs5/zG+q5AEfCdPBDZKoOPM3GsSFg0ysudbMhxYI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PdOII6RH9kC1nW2NlNxCkQzAaSrbwyfJm9hOsB7grL0tx9y+EU0jaKwlvWNa+mWAX dk9Kf/QASWSmsRah/mGqksuXYUah1O2NAwhqWihGdMzlqRwwXOrE4to+DYCVROjI+j YIo7I02SZJSR7pIGX152i4Zg7eF9tXwbyVR526HSZ5wmERG6lgz4hjB4vziS+2yo8i KRBRNNGdeiqYN+IMWfWzqFE/ltGTztAM6BdWa+yqWdmkCp/vIvrrsUrd/8Y3nTWaWj aMroU9gExuLwYBuneUKbcTAWg3s2L0EuIeSZhznFaGjctp8wrcTN6QeFwzBkykoDd4 HXu5Ytki+3VAg== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.1 7/9] mm/damon/core: handle extreme memory state in damon_get_node_mem_bp() Date: Sun, 2 Aug 2026 09:26:28 -0700 Message-ID: <20260802162631.90304-8-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260802162631.90304-1-sj@kernel.org> References: <20260802162631.90304-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: aubgi33eakro5tkjaup6jrkw9botxxkp X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C5AA6100006 X-Rspam-User: X-HE-Tag: 1785688003-346582 X-HE-Meta: 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 Em1CswKq +ki1ZoeJ9kKNtBLOfca20OZasF75jNvxQ/16lFJoos3tBFbmN2ogAY4N9zs2R8eHJ7rmIyzyTitAM3b/8VtZD0lZqDRjP+3iBIdOqsLsxnAyRh9IYfX5eFbzQ3STkY7lVKqjCpiDbcrNI/NWhqqiXZZX8zWMCRncw3YqHlWj69HGmn3IWJj2bqdYVUT39SGb53qFVJtGA4Cb4okOijusePmblQqxUUWL0CzruP8f4CGsKwGyDA1oIsg1Twc8TvxdL7pF6cDNri1otnR4FMS5ahCOghQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: In an extreme and unlikely situation, si_meminfo_node() might let the caller show zero total ram. That could cause a divide by zero in damon_get_node_mem_bp(). Fix it by setting the totalram one byte in the case. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260328133216.9697-1-sj@kernel.org Fixes: 0e1c773b501f ("mm/damon/core: introduce damos quota goal metrics for memory node utilization") Cc: # 6.16.x Signed-off-by: SJ Park --- mm/damon/core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 3bdbf4fbf7147..e3f3ee75a3d33 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2816,10 +2816,16 @@ static __kernel_ulong_t damos_get_node_mem_bp( } si_meminfo_node(&i, goal->nid); - if (goal->metric == DAMOS_QUOTA_NODE_MEM_USED_BP) + if (!i.totalram) + return 10000; + if (goal->metric == DAMOS_QUOTA_NODE_MEM_USED_BP) { numerator = i.totalram - i.freeram; - else /* DAMOS_QUOTA_NODE_MEM_FREE_BP */ + } else { + /* DAMOS_QUOTA_NODE_MEM_FREE_BP */ + if (i.totalram < i.freeram) + return 0; numerator = i.freeram; + } return mult_frac(numerator, 10000, i.totalram); } -- 2.47.3