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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 A29BEC3A5A8 for ; Wed, 4 Sep 2019 19:02:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 788CE208E4 for ; Wed, 4 Sep 2019 19:02:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567623722; bh=A0p265L38NV6UyAt6+h0NKJkV9Yhds5FJHvN1ygxV4c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=auxslNzn0dnvy+/26wGd1j5yVbj5Zx6eCWL9dnByyg7EXT9hSeBE0MW7uE0KbCk+y BaFfNs1Mh0qWHYe1xva2KH767f1oxE4oGiBsATCs1wxB/EDHvOn8E5VkFaPgQvqmXe R8MSqpRESr1Y30JcVgKx7Fm+FZD5myTPw9bnbZEE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387973AbfIDTCB (ORCPT ); Wed, 4 Sep 2019 15:02:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:50772 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730410AbfIDTCB (ORCPT ); Wed, 4 Sep 2019 15:02:01 -0400 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 DE7CD2087E; Wed, 4 Sep 2019 19:01:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567623720; bh=A0p265L38NV6UyAt6+h0NKJkV9Yhds5FJHvN1ygxV4c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=pDxHacczS7aRbBpwyiXA4vrhf5y08lCIaa7YP/dIu1wq26LCRg6bclT5fKTTVLyGH 1U3klZixQDuOyfP5k6u7kLvIMKM4+3SRc7wXpKnAnVKk8yB7IRbiJtdR3maDYRkAfA mu7Oteopa+BITB2kX1vIAZjqSCc0R63PbOkQ7VYE= Date: Wed, 4 Sep 2019 12:01:59 -0700 From: Andrew Morton To: Vlastimil Babka Cc: zhong jiang , mhocko@kernel.org, anshuman.khandual@arm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ira Weiny , "Aneesh Kumar K.V" Subject: Re: [PATCH] mm: Unsigned 'nr_pages' always larger than zero Message-Id: <20190904120159.d4026b573f419838d77e991d@linux-foundation.org> In-Reply-To: <5505fa16-117e-8890-0f48-38555a61a036@suse.cz> References: <1567592763-25282-1-git-send-email-zhongjiang@huawei.com> <5505fa16-117e-8890-0f48-38555a61a036@suse.cz> 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 4 Sep 2019 13:24:58 +0200 Vlastimil Babka wrote: > On 9/4/19 12:26 PM, zhong jiang wrote: > > With the help of unsigned_lesser_than_zero.cocci. Unsigned 'nr_pages"' > > compare with zero. And __get_user_pages_locked will return an long value. > > Hence, Convert the long to compare with zero is feasible. > > It would be nicer if the parameter nr_pages was long again instead of unsigned > long (note there are two variants of the function, so both should be changed). > > > Signed-off-by: zhong jiang > > Fixes: 932f4a630a69 ("mm/gup: replace get_user_pages_longterm() with FOLL_LONGTERM") > > (which changed long to unsigned long) > > AFAICS... stable shouldn't be needed as the only "risk" is that we goto > check_again even when we fail, which should be harmless. > Really? If nr_pages gets a value of -EFAULT from the __get_user_pages_locked() call, check_and_migrate_cma_pages() will go berzerk? And does __get_user_pages_locked() correctly handle a -ve errno returned by __get_user_pages()? It's hard to see how...