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 16950C2BB1D for ; Fri, 13 Mar 2020 03:57:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CE75E20751 for ; Fri, 13 Mar 2020 03:57:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="igO6WyhX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE75E20751 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 7C7636B0005; Thu, 12 Mar 2020 23:57:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 779B56B0006; Thu, 12 Mar 2020 23:57:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 68FC26B0007; Thu, 12 Mar 2020 23:57:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0225.hostedemail.com [216.40.44.225]) by kanga.kvack.org (Postfix) with ESMTP id 4D0CA6B0005 for ; Thu, 12 Mar 2020 23:57:44 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 09913181AEF3C for ; Fri, 13 Mar 2020 03:57:44 +0000 (UTC) X-FDA: 76588980048.30.line94_7dafc215e7808 X-HE-Tag: line94_7dafc215e7808 X-Filterd-Recvd-Size: 2986 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Fri, 13 Mar 2020 03:57:43 +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 7A9B72072F; Fri, 13 Mar 2020 03:57:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584071862; bh=w+ZZsFzaN02z4LjftM7wNgCAMWF+UZWUmlO2OdveGgo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=igO6WyhXDpgdYdsk1Lro4MZ9Kz09lJRzqTA9EBGjn+aZktwUnpRiZ9PNyUYo98e65 ymzJ0f1po2wfMTl+Xp4p7XbDObPJ8SO5dXdTZEk3Ss9M+2rWfMhSb5TX9LZ+4jOZet WA2j+tJuJdOcvRRUh/seQTOBB1Smmxy5aLYSDRMg= Date: Thu, 12 Mar 2020 20:57:41 -0700 From: Andrew Morton To: Souptick Joarder Cc: =?ISO-8859-1?Q?J=E9r=F4me?= Glisse , Linux-MM , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/hmm.c : Remove additional check for lockdep_assert_held() Message-Id: <20200312205741.e97a201037103bbf51e1df40@linux-foundation.org> In-Reply-To: References: <1584065460-22205-1-git-send-email-jrdr.linux@gmail.com> <20200312195850.29693d4e55ec27ae11443c0f@linux-foundation.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Fri, 13 Mar 2020 09:17:22 +0530 Souptick Joarder wrote: > On Fri, Mar 13, 2020 at 8:28 AM Andrew Morton wrote: > > > > On Fri, 13 Mar 2020 07:41:00 +0530 Souptick Joarder wrote: > > > > > walk_page_range() already has a check for lockdep_assert_held(). > > > So additional check for lockdep_assert_held() can be removed from > > > hmm_range_fault(). > > > > > > ... > > > > > > --- a/mm/hmm.c > > > +++ b/mm/hmm.c > > > @@ -681,7 +681,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags) > > > struct mm_struct *mm = range->notifier->mm; > > > int ret; > > > > > > - lockdep_assert_held(&mm->mmap_sem); > > > > > > do { > > > /* If range is no longer valid force retry. */ > > > > It isn't very obvious that hmm_range_fault() is and will only be called > > from walk_page_range() (is it?) > > > > Sorry Andrew, didn't get this part ? > * hmm_range_fault() is and will only be called > from walk_page_range() (is it?) * The patch assumes that hmm_range_fault() will only ever be called via walk_page_range(). How do we know this is the case? And that it always will be the case?