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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 7B046C433E4 for ; Tue, 28 Jul 2020 13:57:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5C050207E8 for ; Tue, 28 Jul 2020 13:57:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="eyumjyR+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730253AbgG1N5B (ORCPT ); Tue, 28 Jul 2020 09:57:01 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:60609 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726764AbgG1N5A (ORCPT ); Tue, 28 Jul 2020 09:57:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595944619; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vfTc1Sd6o29rE/cL2xWa+D8N0CUv3nwmUtcS2HIpsf4=; b=eyumjyR+kdaQbwLKZnpainUZ6yqCXVqojQLs2sahjK6/KoAKWZn6syRjGGBLHUWhmzmmaM Z6PNBJ6t1NVmNaUMZFda8qJPSHVa06w8wSR/XZB3LQtNKBWN2Wb2QpcBC3NHsOGTrr1ZMt kt037SfPhuYaY1hJSERpOz8iw9gcpws= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-367-hcivNEh2MGC1nzKRmhLHDg-1; Tue, 28 Jul 2020 09:56:55 -0400 X-MC-Unique: hcivNEh2MGC1nzKRmhLHDg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 17FA0800460; Tue, 28 Jul 2020 13:56:54 +0000 (UTC) Received: from localhost (ovpn-12-117.pek2.redhat.com [10.72.12.117]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7C9E575543; Tue, 28 Jul 2020 13:56:45 +0000 (UTC) Date: Tue, 28 Jul 2020 21:56:41 +0800 From: Baoquan He To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, Andrew Morton , Michal Hocko , "Michael S . Tsirkin" Subject: Re: [PATCH v1 2/6] mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate() Message-ID: <20200728135641.GD14854@MiWiFi-R3L-srv> References: <20200630142639.22770-1-david@redhat.com> <20200630142639.22770-3-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200630142639.22770-3-david@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/30/20 at 04:26pm, David Hildenbrand wrote: > Right now, if we have two isolations racing, we might trigger the > WARN_ON_ONCE() and to dump_page(NULL), dereferencing NULL. Let's just > return directly. > > In the future, we might want to report -EAGAIN to the caller instead, as > this could indicate a temporary isolation failure only. > > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Michael S. Tsirkin > Signed-off-by: David Hildenbrand > --- > mm/page_isolation.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index f6d07c5f0d34d..553b49a34cf71 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -29,10 +29,12 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ > /* > * We assume the caller intended to SET migrate type to isolate. > * If it is already set, then someone else must have raced and > - * set it before us. Return -EBUSY > + * set it before us. > */ > - if (is_migrate_isolate_page(page)) > - goto out; > + if (is_migrate_isolate_page(page)) { > + spin_unlock_irqrestore(&zone->lock, flags); > + return -EBUSY; Good catch, the fix looks good to me. Reviewed-by: Baoquan He > + } > > /* > * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. > -- > 2.26.2 > >