From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EE282200B8 for ; Fri, 20 Oct 2023 17:23:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R2Uo8d1d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 744D4C433C9; Fri, 20 Oct 2023 17:23:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697822608; bh=A7qQGX2x61HuX9WngSjrxy/tMdxThwG7cO+vlCnt/oI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R2Uo8d1dOObRxHmQhvT+GaBkbeipS3EDjJHzlrqnXCOqDtzreW0cAfNfLBKnVc8lc lCprkGxeggXj98oVNf/z2gNIDicTFnmBoUSvD8XtZKmqF8BGuA1vA5ufLZh4OjhNfY xc9+xQc4jg/efEPeUXH3jErpnXwLGo738cZmOScqm/dYnZfejUTXwGj+LjFdURrRTu pAbE3gO8gyfQ/zOq8DRIK0aUFpnm+GIxyJPhGLoPRDPqkfz3HJWzOyFpKlnff7OBsQ 1he8H2Uc1OZyM9peBjSqaiWiqy51/HuuUooffHS1eN5ncUvPAJQtvNwZEIHW/YnzZt O2zyOi3nvaUSA== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation Date: Fri, 20 Oct 2023 17:23:17 +0000 Message-Id: <20231020172317.64192-6-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231020172317.64192-1-sj@kernel.org> References: <20231020172317.64192-1-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 When calculating the pseudo-moving access rate, DAMON divides some values by the maximum nr_accesses. However, due to the type of the related variables, simple division-based calculation of the divisor can return zero. As a result, divide-by-zero is possible. Fix it by using damon_max_nr_accesses(), which handles the case. Note that this is a fix for a commit that not in the mainline but mm tree. Fixes: ace30fb21af5 ("mm/damon/core: use pseudo-moving sum for nr_accesses_bp") Signed-off-by: SeongJae Park --- Note that this is for a patch in mm-stable that not yet merged into the mainline. 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 e194c8075235..aa2dc7087cd9 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1665,7 +1665,7 @@ void damon_update_region_access_rate(struct damon_region *r, bool accessed, * aggr_interval, owing to validation of damon_set_attrs(). */ if (attrs->sample_interval) - len_window = attrs->aggr_interval / attrs->sample_interval; + len_window = damon_max_nr_accesses(attrs); r->nr_accesses_bp = damon_moving_sum(r->nr_accesses_bp, r->last_nr_accesses * 10000, len_window, accessed ? 10000 : 0); -- 2.34.1