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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F094C282C2 for ; Wed, 13 Feb 2019 14:30:30 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5DBA2222B2 for ; Wed, 13 Feb 2019 14:30:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OnDzWJxI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5DBA2222B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=2xcaDn8wEMxYnSKGYgJxRZ4aXTtBk/nbZz4+I3x64kk=; b=OnDzWJxIy7kKrY Hbzt3y2BLmk9vOVIrEgEKOGDNdXpmhpTmhVkMZsAthfFB3nBPdVbQJnztS0DPx4uyV38lUW/i2var 689dNzeZDX0s42q9NeAZQJfSg1jb7TfSegAWgMEbIATPuEa91FeSn03TPgzW2c4Y1F+b7gN4L+BVm mg05PC+lEPZ8Bn2koN78TVWx8wZbGd11kq01dZT2Vx/QxDgL6OgOVnXuKwHIg0j/beim0ZZBVZ78H XX7fgKIfvOxygHBeu3lcR7JqCZwnjQ54EOQYCgJjByWoVn5kCmuCN4gBor6LAcOl6rQjoI2kolqbO 7Wb2EMgF1LZl5cC1bzSQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gtvYM-00059a-1l; Wed, 13 Feb 2019 14:30:22 +0000 Received: from outbound-smtp04.blacknight.com ([81.17.249.35]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gtvYI-00058e-0u for linux-arm-kernel@lists.infradead.org; Wed, 13 Feb 2019 14:30:19 +0000 Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp04.blacknight.com (Postfix) with ESMTPS id 9211998A96 for ; Wed, 13 Feb 2019 14:30:14 +0000 (UTC) Received: (qmail 2776 invoked from network); 13 Feb 2019 14:30:14 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[37.228.225.79]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 13 Feb 2019 14:30:14 -0000 Date: Wed, 13 Feb 2019 14:30:13 +0000 From: Mel Gorman To: Andrew Morton Subject: [PATCH] mm, page_alloc: Fix a division by zero error when boosting watermarks v2 Message-ID: <20190213143012.GT9565@techsingularity.net> References: <20190213131923.GQ9565@techsingularity.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190213131923.GQ9565@techsingularity.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190213_063018_199249_46123896 X-CRM114-Status: GOOD ( 12.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrea Arcangeli , Yury Norov , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Michal Hocko , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, David Rientjes , Vlastimil Babka Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Yury Norov reported that an arm64 KVM instance could not boot since after v5.0-rc1 and could addressed by reverting the patches 1c30844d2dfe272d58c ("mm: reclaim small amounts of memory when an external 73444bc4d8f92e46a20 ("mm, page_alloc: do not wake kswapd with zone lock held") The problem is that a division by zero error is possible if boosting occurs very early in boot if the system has very little memory. This patch avoids the division by zero error. Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs") Reported-and-tested-by: Yury Norov Tested-by: Will Deacon Signed-off-by: Mel Gorman --- mm/page_alloc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d295c9bc01a8..bb1c7d843ebf 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2170,6 +2170,18 @@ static inline void boost_watermark(struct zone *zone) max_boost = mult_frac(zone->_watermark[WMARK_HIGH], watermark_boost_factor, 10000); + + /* + * high watermark may be uninitialised if fragmentation occurs + * very early in boot so do not boost. We do not fall + * through and boost by pageblock_nr_pages as failing + * allocations that early means that reclaim is not going + * to help and it may even be impossible to reclaim the + * boosted watermark resulting in a hang. + */ + if (!max_boost) + return; + max_boost = max(pageblock_nr_pages, max_boost); zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages, -- Mel Gorman SUSE Labs _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel