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b=ofUbJFVR7en0yO0u2gPuMSNQGF9LpRv6jXSWh8QWsDr0ac+40r0HMmVvt7WTuctK1 KQLtO97awGBVMnLh4R8Vqj+ZtTKLPAVpJXiGf5mLcmpdIqLCCAThLDY1lhwcaBm0cs VW1NZJPqcEPC/AxOP1D/ukzLmOuZZQ6Ka0krAe4nah7mQm8hSpJtEmUMOyJnWHlyzW 5/sb1DYCZq8M60TAb7NKEFbgs1zJ30rqFC0apy1d3FYlAOr6nooymr0K0QaDyqGB+g mx/1InCGj+lfKu+6C4CK9X2mqg3dDC3AR1olcCKFxgT+N8+TTvMDDxtLlzF30mykpc WymgJ8KHGWQLQ== 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 9/9] mm/damon/core: handle extreme memory state in get_in_active_mem_bp() Date: Sun, 2 Aug 2026 09:26:30 -0700 Message-ID: <20260802162631.90304-10-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-Rspamd-Queue-Id: 712D814000F X-Stat-Signature: kpzp41kp59g3ofcq1u73nqrxgirkx9ra X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1785688004-971433 X-HE-Meta: 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 YcZruZGx S/AI1pph1T/rnNE8wzXsxp/lxriKrT3gVozpRKdVMnHJshvTJraG5bT6HASAurCIEVfTgARzqMvZq30oMsZR9maeZf5XKNsAnBHYOBYQeTO/jAX7/jl79gK0Fo9Nb8TOHSi6iE5QvgefDndAzF7xdjA+tNeNsx3wq+7pw3LbUo95DKGofLMLCp5hnVz/vbEIuAbYeExC3Kpgh6hX1V4J5AcnYYToAm44PaQfpyTsZYBVUzxMMx+U9m0vIocD/sc2mO1dPjmVTvs30ZiD/9C44NaZK7A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damos_get_in_active_mem_bp() uses the sum of the active and inactive memory amount as a denominator. In an extreme and unlikely environment, active and inactive memory might be zero. In this case, hence, it results in a divide by zero problem. Avoid it by changing the denominator to one if it is zero, before it is being used. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260721034756.147011-1-sj@kernel.org Fixes: 4835e2871321 ("mm/damon/core: introduce [in]active memory ratio damos quota goal metric") Cc: # 7.0.x Signed-off-by: SJ Park --- mm/damon/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 67ad1f07c29a4..c79b854e1a971 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -3014,7 +3014,7 @@ static unsigned int damos_get_in_active_mem_bp(bool active_ratio) global_node_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE); inactive = global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_ANON) + global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE); - total = active + inactive; + total = max(active + inactive, 1); if (active_ratio) return mult_frac(active, 10000, total); return mult_frac(inactive, 10000, total); -- 2.47.3