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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 82C60C432C0 for ; Mon, 18 Nov 2019 21:02:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3FCCE2230D for ; Mon, 18 Nov 2019 21:02:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="n+6S+KFJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3FCCE2230D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D30C96B0007; Mon, 18 Nov 2019 16:02:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CE1B46B0008; Mon, 18 Nov 2019 16:02:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BF7BF6B000A; Mon, 18 Nov 2019 16:02:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0217.hostedemail.com [216.40.44.217]) by kanga.kvack.org (Postfix) with ESMTP id A9FDC6B0007 for ; Mon, 18 Nov 2019 16:02:51 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 6BB7D3CE9 for ; Mon, 18 Nov 2019 21:02:51 +0000 (UTC) X-FDA: 76170622542.14.range07_8d4bd67447205 X-HE-Tag: range07_8d4bd67447205 X-Filterd-Recvd-Size: 3135 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Mon, 18 Nov 2019 21:02:50 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 814232230C; Mon, 18 Nov 2019 21:02:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574110969; bh=a9vMYyllcb3gUHdpiiVPt9cfrewV13thVHZ2UmvwyMk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=n+6S+KFJNTvRFatmv8GN66bVEgtHZ9W5jOJRCrH0LLcp8HDqVSa77ahulo1tUvtQu C78BVV99K6wTdF6bUZjr6svwQcJ7hTq+M/sQR3s0YrThMMuloVhUgBebZ9ev4i7csn 2ePpEzt1DJfF7RKmaWYXJGYUkKzSP+1kVIr8GEjo= Date: Mon, 18 Nov 2019 13:02:49 -0800 From: Andrew Morton To: Thomas =?ISO-8859-1?Q?Hellstr=F6m?= (VMware) Cc: "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Hellstrom , Arnd Bergmann , "Kirill A. Shutemov" , Matthew Wilcox Subject: Re: [PATCH 2/2] mm: Fix a huge pud insertion race during faulting Message-Id: <20191118130249.2ec96ffdf9a1aeb4f3e820dd@linux-foundation.org> In-Reply-To: References: <20191115115808.21181-1-thomas_os@shipmail.org> <20191115115808.21181-2-thomas_os@shipmail.org> <20191115115800.45c053abcdb550d70b9baec9@linux-foundation.org> <20191118102219.om5monxih7kfodyz@box> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 18 Nov 2019 13:58:04 +0100 Thomas Hellstr=F6m (VMware) wrote: > >> Is a -stable backport warranted? > > I believe it is. >=20 > Note that this was caught during a code audit rather than a real=20 > experienced problem. It looks to me like the only implementation that=20 > currently creates huge pud pagetable entries is dev_dax_huge_fault()=20 > which doesn't appear to care much about private (COW) mappings or=20 > write-tracking which is, I believe, a prerequisite for create_huge_pud()= =20 > falling back on thread 1, but not in thread 2. >=20 > This means (assuming that's intentional) that a stable backport=20 > shouldn't be needed. >=20 > For the WIP huge page support for graphics memory we'll be allowing both= =20 > COW mappings and write-tracking, though, but that's still some time away. >=20 > In any case, I think this patch needs -rc testing to catch potential=20 > pud_devmap issues before submitted to stable. OK, thanks, I'll queue it for 5.5-rc1 with a -stable tag. Hopefully that way it will get a bit of exposure before the stable trees pick it up. Maybe this is optimistic..