From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39A5B3B774D; Sat, 1 Aug 2026 17:36:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785605768; cv=none; b=NNMq5qE7i0UVlUkbsncONsDu1NxMAZiYNQGFNvfsf2C1wIvMGAqYofkzW+Vf2f47xQvvUTcdyS/BSnUOv5NTSxzgeRwRQKB100GRFSxdnt3sHlVhKASTbqOXL3iPy8oVlM+pVGbrDolZdbF/n6Ibf6b2Y3t5Ts4CQWYLe0YX3eE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785605768; c=relaxed/simple; bh=KjoY84pOsntbTzs2pYQd5yUSWCVGO50nSKIZh/b5N2Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cG229i3Gk23CPXq8vPD61e7zFn76gxIlYORQsnCzYvavAbivXZc5idUStcsrLXc5mk3xu7+ZJUvqz15cOSZZP5ME4IYqdCpexBVo5vABpdv6gAcSgEDxdfzsKI9KMAXfHhr80Tn+vT9q8pj6H0plqNT1yMx0L5plxz451mAElrc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dBhdoT/o; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dBhdoT/o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFDBA1F00ACF; Sat, 1 Aug 2026 17:36:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785605766; bh=o1TLO1J6QDVVNz5r0BRdl5+1+gHGcHEvIPNqhuz3/rg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dBhdoT/oGy8uRNBe84+vYOBuny3Wc3DU+omPxB8qCyOOhCnd7o9VPHfTLGSr0svTm WIVpXEAo95W2gFYNTc60Q/WrtdVkwUCPxrXFqI0aCS1pvhIFlzieCAPUArKSzS7M7E WiCSPcSHFSaorwfw1JYkCD+X/Z6b8UycD0GVzoa6YTU6LaSH+i8jYQ4BqC3u4nkN50 aVM3BZ6dyZVLl5ekBfmG8Qzr27Ok+q7YLzONrQq1/3z9fWr02hCNBH7/Bbv78Ez8kf DORcHdnxEUA7CGYp9TRVu0eCFvk35jcx2SgKzYvpD57ijKfUj4y99iyAUR1EaPkGGM LadBoeJhACBfg== 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 7/9] mm/damon/core: handle extreme memory state in damon_get_node_mem_bp() Date: Sat, 1 Aug 2026 10:35:50 -0700 Message-ID: <20260801173554.94710-8-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260801173554.94710-1-sj@kernel.org> References: <20260801173554.94710-1-sj@kernel.org> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index 3bdbf4fbf7147..269865eb8fbfa 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2816,6 +2816,8 @@ static __kernel_ulong_t damos_get_node_mem_bp( } si_meminfo_node(&i, goal->nid); + if (!i.totalram) + i.totalram = 1; if (goal->metric == DAMOS_QUOTA_NODE_MEM_USED_BP) numerator = i.totalram - i.freeram; else /* DAMOS_QUOTA_NODE_MEM_FREE_BP */ -- 2.47.3