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 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 EAAACC47247 for ; Thu, 30 Apr 2020 21:23:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A154C2166E for ; Thu, 30 Apr 2020 21:23:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="QAitjNdy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A154C2166E 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 267E68E0005; Thu, 30 Apr 2020 17:23:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 218348E0001; Thu, 30 Apr 2020 17:23:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 107DB8E0005; Thu, 30 Apr 2020 17:23:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0212.hostedemail.com [216.40.44.212]) by kanga.kvack.org (Postfix) with ESMTP id EA5F98E0001 for ; Thu, 30 Apr 2020 17:23:13 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id B42054417 for ; Thu, 30 Apr 2020 21:23:13 +0000 (UTC) X-FDA: 76765797066.08.twig37_7375652e9c232 X-HE-Tag: twig37_7375652e9c232 X-Filterd-Recvd-Size: 2101 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Thu, 30 Apr 2020 21:23:13 +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 302412166E; Thu, 30 Apr 2020 21:23:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588281792; bh=64VkPdoiN0OePS1AJNJImnN0TBSj5RZkl5WHr7pH2zc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=QAitjNdyFZAKZsl9w/HSamjjGQ43tPG20k8YV2BhA6BAzLoL8vXNaWoF9UMgfQlOl pz18SKiCyaRhywDfyy1jCV0/LK15E/q4uBqFP8Tx1y3f51UjeysrNXGr/bRGdaLgLN gix2QWqIln1sTlUAN7qwXwkBNh3ycqNJqvImuaK4= Date: Thu, 30 Apr 2020 14:23:11 -0700 From: Andrew Morton To: Souptick Joarder Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/gup.c: Handle error at earliest for incorrect nr_pages value Message-Id: <20200430142311.091b82235141ca47b9c6475a@linux-foundation.org> In-Reply-To: <1588277518-21425-1-git-send-email-jrdr.linux@gmail.com> References: <1588277518-21425-1-git-send-email-jrdr.linux@gmail.com> 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=0.004628, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 1 May 2020 01:41:58 +0530 Souptick Joarder wrote: > As per documentation, pin_user_pages_fast() & get_user_pages_fast() > will return 0, if nr_pages <= 0. But this can be figure out only after > going inside the internal_get_user_pages_fast(). > > This can be handled early. Adding a check for the same. Calling get_user_pages() for (nrpages <= 0) is a nonsensical thing to do so it isn't a thing we should care to optimize. Adding new checks will actually slow down the use cases which we *do* care about. And it adds more code.