From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 96456C624D5 for ; Tue, 1 Sep 2026 13:19:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 81EC96B0199; Tue, 1 Sep 2026 09:19:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7F7B56B019C; Tue, 1 Sep 2026 09:19:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 733A36B019D; Tue, 1 Sep 2026 09:19:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 546B26B0199 for ; Tue, 1 Sep 2026 09:19:04 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id D4C961A0405 for ; Tue, 1 Sep 2026 13:19:03 +0000 (UTC) X-FDA: 85165248966.24.D303FBC Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf12.hostedemail.com (Postfix) with ESMTP id 3DF104000A for ; Tue, 1 Sep 2026 13:19:02 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ig92mQta; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788268742; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=VvO9nu/pvwrT8AJnGanMkEVbhfeAa8vp4BSGaiM1GXg=; b=BIPaeIpECS0jiFYWv1Gjp/duM396sqemT0+QY6hg1uZeJZuRC1nofPynapoLLkgnLFwMk7 MR+kTi4FNb92Y7d3SFajm9g24OrRaWdUIIMG8msfhoNGNYlAxuUJ/jzoC/s3eq6/RcoYGN AUZVuMttp23wcBuy1JIvkxQF02dS+T4= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ig92mQta; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788268742; b=DQY5yK5JdKucadwFIDFhwxoARLQJ7E9hd4LjTQUHfaLPHX7dzqLhtbvfdopYFZFm1AKp+c 8YmpgwKaarVnC7LCyvSDVZlX2r2jgynfwQBcSoWnX1EmvwtVT+5k4CiCPHq/zobIJvUtvf 6zLRII9jMZx96KW8PuHSAQwcDBLHcvA= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 911B642EA5; Tue, 1 Sep 2026 13:19:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 452D01F00A3E; Tue, 1 Sep 2026 13:19:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788268741; bh=VvO9nu/pvwrT8AJnGanMkEVbhfeAa8vp4BSGaiM1GXg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ig92mQtakTdHt0VVFboiQzpG74wWcUaalH06d9B8H+DqFvf8O10xsK8agpzNt48dI J6z78dAJsmkAgL1bGwzouj7Bo1tsFXUwjGUhxaemvkiP5iJj5I27039kzIr6sPksz/ JmcUMbUDgwzghHaFtsLePi+nD/8bOnxkGtErWkZTfW+jquJlWqsN8qC0LBAV4yE2Mh E6LBN4vo828WsQkUMz4FEZZroCbmbvGpWvYiJZv6EeK+4lqNiYuxidJqZjeLKjMtPt iXRCXVLksLVM8WMlccLkVlGFJDyXyLeFnLG3uFITa+I94BxAVO5fXbh2YuVmqx6CPS uPIFRnMKnnwDg== From: SJ Park To: Andrew Morton Cc: SJ Park , stable@vger.kernel.org, damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 8/8] mm/damon/core: handle extreme memory state in get_in_active_mem_bp() Date: Tue, 1 Sep 2026 06:18:49 -0700 Message-ID: <20260901131850.98037-9-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260901131850.98037-1-sj@kernel.org> References: <20260901131850.98037-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 3DF104000A X-Stat-Signature: rhe9kwsqf1x7yqodsyrr59a36tkyzq5y X-Rspam-User: X-HE-Tag: 1788268742-369728 X-HE-Meta: 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 sd3D4BGm jpetKan/OTdzaWFpbcx0NC5iKPSUpwus/ukD8KEN52If4hynUADfz9OME53NUdEl7gza6NZVeNKcSI11Tb7U/pKgxYeHbqZiU7cqRCf6m6X/S0P2aAcQuRaRP1sjjnyUuJ1cGqHDqtpZKF7v3VaTrT9mR8SFVQJ/jp6/NbtODI04UGnSTiF0U8yecDq0QwP11EaHFrXVb57CmgXqd2viXl+KSpqVQU8/569fd1rAa4wFl8GTsUIwuuA2YztNzyaTVhzVkCmmggaiTn8GexTUnNqmTuw== 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 3060edf5e4fa6..0df785e72438f 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -3006,7 +3006,7 @@ 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