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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,USER_IN_DEF_DKIM_WL 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 5A3DCC28CF6 for ; Thu, 26 Jul 2018 16:40:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 152D32089B for ; Thu, 26 Jul 2018 16:40:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QHqfnMGl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 152D32089B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733186AbeGZR6I (ORCPT ); Thu, 26 Jul 2018 13:58:08 -0400 Received: from mail-yb0-f196.google.com ([209.85.213.196]:36829 "EHLO mail-yb0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731801AbeGZR6I (ORCPT ); Thu, 26 Jul 2018 13:58:08 -0400 Received: by mail-yb0-f196.google.com with SMTP id s1-v6so891524ybk.3 for ; Thu, 26 Jul 2018 09:40:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=Pbzvirt74+CocRnPvyDxieVSgr06qHyxp3sIpx6ZmkU=; b=QHqfnMGl7NwuJ2KyUI87PEfIFKGwLkG3Rmnpzpw2QRqotlIVG6UkU/w12ABpqgeS0z JuelfRcIRGiGiEuG3cTXe/F/rADH7XwO1GCSnXWu9vAnUi8YRMODR09wb0R7Xx+r05Fz 6asOnUwv6MQ6RvJY73Xlb1hTxUqNMxdpqn1qB+uhdfR1Q0MraM1fkOyqy1ZFIGHAbfNu cQ+7ji6np1R2LBiMCcCQdYAiMGqTbynZbJbllSQaI8tRIFaxtSb9cAp/OkzmS4Mw2ikO O3lSGag5GUQaxR/nNpCgVmBOlCtxgWiyK7FU4ZFxUUY35we9VN5Ac4GkO4zkABZUgA6Z N1gQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=Pbzvirt74+CocRnPvyDxieVSgr06qHyxp3sIpx6ZmkU=; b=pl0g1zuhJhB0TBWWjWYEpi/wtKFvRwPucG3k9iLeNpCx8e2lJKBdTJuEOLsseIQoTE FYty/awZYWrSu7i0mtvwqIVilGnIHONCjPkPgkKiz4eXvR0ORbcJsFRDNEhjGP2DZntR DJbSZ7oyvkDgJ5mlQQ2+GBV2wZ4gE3vsgm0vAnYPUCy6LVNHJLimh2cY+s6eKLecGZ+8 ub6qDo4QihBF1D1XWHHoGt5x7Z2Bs8MmukOSLyvGro9t/Ck3QkJQf5I0IIccYkwZvhfX fpsIn0fqEzFiXEFjIyx8FWnceJJjVkltJl744JNMYv92GlOIuscOdH6Lt+GG6jXRbaYZ l7HA== X-Gm-Message-State: AOUpUlFwphLS+h1qVTgA4fMEBGa9wJsRjs7fXHREw2Ku7gY/KJB4glNb dVl8QEzUwP/epf6YepVekA9eFg== X-Google-Smtp-Source: AAOMgpe+bw28tj0oBZpzBy2TzRlOr3EyrBO15vUVXYo6znk3m5cctYyh1Ks6o1H289W5jal6U+UUmQ== X-Received: by 2002:a5b:786:: with SMTP id b6-v6mr1548927ybq.160.1532623229802; Thu, 26 Jul 2018 09:40:29 -0700 (PDT) Received: from eggly.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id d6-v6sm756243ywa.85.2018.07.26.09.40.27 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 26 Jul 2018 09:40:28 -0700 (PDT) Date: Thu, 26 Jul 2018 09:40:20 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Matthew Wilcox cc: Hugh Dickins , syzbot , "Kirill A. Shutemov" , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Subject: Re: kernel BUG at mm/shmem.c:LINE! In-Reply-To: <20180726143353.GA27612@bombadil.infradead.org> Message-ID: References: <000000000000d624c605705e9010@google.com> <20180709143610.GD2662@bombadil.infradead.org> <20180723140150.GA31843@bombadil.infradead.org> <20180723203628.GA18236@bombadil.infradead.org> <20180723225454.GC18236@bombadil.infradead.org> <20180726143353.GA27612@bombadil.infradead.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 26 Jul 2018, Matthew Wilcox wrote: > On Wed, Jul 25, 2018 at 11:53:15PM -0700, Hugh Dickins wrote: > > and fixing the bug differently ;-) But many thanks for spotting it! I thought you might :) > > I'll look into the next bug you reported ... No need: that idea now works a lot better when I use the initialized "start", instead of the uninitialized "index". Hugh --- mmotm/mm/khugepaged.c 2018-07-20 17:54:41.978805312 -0700 +++ linux/mm/khugepaged.c 2018-07-26 09:20:22.416949014 -0700 @@ -1352,6 +1352,7 @@ static void collapse_shmem(struct mm_str goto out; } while (1); + xas_set(&xas, start); for (index = start; index < end; index++) { struct page *page = xas_next(&xas);