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 0214A32AAB5; Fri, 9 Jan 2026 12:20:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767961231; cv=none; b=C+1wImDZjz7Ve4lNm74ivZGr/ppUtkESkBPvjVtdpyjmXTjF4008DnVXaaLcihQt5CF9yoQijF9yunaFGlJSaNAPHHIdcvDTy/H7lY/B13f9q8jYJsV3Rm8/k+tXLYMFQDdXg8MtYUyLlzaMF+DSeZh9UkPw2Eb/W6AuBuycknY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767961231; c=relaxed/simple; bh=wouDCOrxsWLOgQjLWg0n19PCQ7Uye3Y6aqEdWm8EcL0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MTQweIJXZBboS7W+zNLXzg7EhskollZXf/3ibv0X4eUn1kU8AmfBd99GFCqTijYau+kQuIC711PAETaW+9yidfJ6lQZssaSJ8KGWmFkQxzSUCkr1Zqt9Q3eJFRrdYqaePTJoQFrvhNTHUNMZf0EGd+pVD7LIuQ0V6eNRHGvHAwc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yqeaWEJY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="yqeaWEJY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7923CC4CEF1; Fri, 9 Jan 2026 12:20:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767961230; bh=wouDCOrxsWLOgQjLWg0n19PCQ7Uye3Y6aqEdWm8EcL0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yqeaWEJY3uirT2vOU1EAxFgziwV9+0wDvyGxNhw/JovnmQtCUGD3Qe45x5GbWkYAc x5fx8o5yIwIiJIo1yM6/lR0HdQF2FIRQTEkB/01QRVAUXUhO+JbFvKH2qPDUxasixL bhz1tkDeG03JyOrNillvoEaTikO456Q70zQlarbs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, jefflexu@linux.alibaba.com, Joseph Qi , "Matthew Wilcox (Oracle)" , Stefan Roesch , Andrew Morton Subject: [PATCH 6.6 681/737] mm: fix arithmetic for bdi min_ratio Date: Fri, 9 Jan 2026 12:43:40 +0100 Message-ID: <20260109112159.673905192@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112133.973195406@linuxfoundation.org> References: <20260109112133.973195406@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jingbo Xu 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 Signed-off-by: Greg Kroah-Hartman --- mm/page-writeback.c | 1 - 1 file changed, 1 deletion(-) --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -714,7 +714,6 @@ static int __bdi_set_min_ratio(struct ba 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) {