From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out199-10.us.a.mail.aliyun.com (out199-10.us.a.mail.aliyun.com [47.90.199.10]) (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 DAC6F211A09 for ; Thu, 11 Dec 2025 02:40:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=47.90.199.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765420835; cv=none; b=szNDVVo8Yt0jT6WZzfLSrwYh2bDZXypUexV+ePyQLH/2XRrXay9mahSw4q2wIEXPmO+zwfcK9MBtUKyf7nwJ6nJhRH9prq69mNKjkQhHklKoyZcTwjej+g93OXV96tuYDngwIKiKsyF6gfPIsTVqRBhd6XBQvdDGeKoqZz0PtDI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765420835; c=relaxed/simple; bh=cirWTS0LYIYbrnVJLOiUqh0OW2IWTcDe6RNYZmDYLfI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=qEFnVLWn+jOeigUnlW7OSdk+unA+3YPkZ77jokBnLdzlbCKTWgJNiJ9dCGF00syy17sRcOQJ/O+6h9fFkyvxMripHg/7qT24kiDR3w8teJUPW65BCm+wo+aTBQeZ6zxHnH1hYkvNhQxNuDku556jMrQUUPq6rFAoa/N/DYeLIhM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=qE3oV74Y; arc=none smtp.client-ip=47.90.199.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="qE3oV74Y" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1765420820; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=hGDsDf2H5VoE3e18JTiN8pilBy3Efg/v3wbdFTaEC3w=; b=qE3oV74YY2vX2ir9MI4qTq48A+NPSO3eQVjI14uif5/p/JqmTl+lTtVtUWPpbM7Rz61SIsAgj8mksLfIhgbpKS1TiLvnm2S5slP57dbcLswKLMVhT6hdkJjbcwH4vNCa4ztDf7gyS0YFaP6MrMIp7F1dHdhNOMCrlQ7hQ1wubhg= Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0WuYZjJE_1765420508 cluster:ay36) by smtp.aliyun-inc.com; Thu, 11 Dec 2025 10:35:09 +0800 From: Jingbo Xu To: gregkh@linuxfoundation.org, sashal@kernel.org, stable@vger.kernel.org Cc: jefflexu@linux.alibaba.com Subject: [PATCH 1/2] mm: fix arithmetic for bdi min_ratio Date: Thu, 11 Dec 2025 10:35:06 +0800 Message-Id: <20251211023507.82177-2-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20251211023507.82177-1-jefflexu@linux.alibaba.com> References: <20251211023507.82177-1-jefflexu@linux.alibaba.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit commit e0646b7590084a5bf3b056d3ad871d9379d2c25a upstream. Since now bdi->min_ratio is part per million, fix the wrong arithmetic. Otherwise it will fail with -EINVAL when setting a reasonable min_ratio, as it tries to set min_ratio to (min_ratio * BDI_RATIO_SCALE) in percentage unit, which exceeds 100% anyway. # cat /sys/class/bdi/253\:0/min_ratio 0 # cat /sys/class/bdi/253\:0/max_ratio 100 # echo 1 > /sys/class/bdi/253\:0/min_ratio -bash: echo: write error: Invalid argument Link: https://lkml.kernel.org/r/20231219142508.86265-2-jefflexu@linux.alibaba.com Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function") Signed-off-by: Jingbo Xu Reported-by: Joseph Qi Cc: Matthew Wilcox (Oracle) Cc: Stefan Roesch Signed-off-by: Andrew Morton --- mm/page-writeback.c | 1 - 1 file changed, 1 deletion(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 9ceb841af819..3929bb0a7501 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -714,7 +714,6 @@ static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ra if (min_ratio > 100 * BDI_RATIO_SCALE) return -EINVAL; - min_ratio *= BDI_RATIO_SCALE; spin_lock_bh(&bdi_lock); if (min_ratio > bdi->max_ratio) { -- 2.19.1.6.gb485710b