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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 3D779C33CB6 for ; Wed, 15 Jan 2020 15:30:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F2B8D2053B for ; Wed, 15 Jan 2020 15:30:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="KTafuKCn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2B8D2053B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8E3788E0008; Wed, 15 Jan 2020 10:30:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8943C8E0003; Wed, 15 Jan 2020 10:30:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 784D28E0008; Wed, 15 Jan 2020 10:30:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0218.hostedemail.com [216.40.44.218]) by kanga.kvack.org (Postfix) with ESMTP id 5E4E18E0003 for ; Wed, 15 Jan 2020 10:30:48 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 11800181AEF0B for ; Wed, 15 Jan 2020 15:30:48 +0000 (UTC) X-FDA: 76380256176.02.sail67_24036c5b5fc07 X-HE-Tag: sail67_24036c5b5fc07 X-Filterd-Recvd-Size: 3875 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Wed, 15 Jan 2020 15:30:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=hlxbWHBq8lfTBkbbWblALE5WfMIrcmCMtir+afT5h7g=; b=KTafuKCnLEQxrDndx0KF1DZxC rnKdoLI6sypMh61W+oBSzZckG9nErVqXpqRux90/jnJHBoNxCmDRhLN16rsx5kcLMMQTzpNlRHW3V Kn+EfBOj9xXDn+MMy1P1Ce1dDs4zbgiDeuR8jQgZiUt61hA4+gx5SghScUnsRQG1ziTZYHV9R9Zgf pJxhgaR5AeWS3+N32IQliDA3Jqotb5XQKegSIoZaLpNN+GhynXNs1L5cGpIhmQbJynCGULBXCRnjC vAgzg7hshbf2g9UxNsiPKchC1nKbZKVYFzdAbYAS/fNwV5Y2i+QhIqJe1mPDizEBhtnZaTAQECgQV KQqONFysg==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1irkce-0002dy-Qu; Wed, 15 Jan 2020 15:30:20 +0000 Date: Wed, 15 Jan 2020 07:30:20 -0800 From: Christoph Hellwig To: John Hubbard Cc: Andrew Morton , Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?iso-8859-1?B?Suly9G1l?= Glisse , "Kirill A . Shutemov" , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , bpf@vger.kernel.org, dri-devel@lists.freedesktop.org, kvm@vger.kernel.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-mm@kvack.org, LKML , Mike Rapoport Subject: Re: [PATCH v12 11/22] mm/gup: introduce pin_user_pages*() and FOLL_PIN Message-ID: <20200115153020.GF19546@infradead.org> References: <20200107224558.2362728-1-jhubbard@nvidia.com> <20200107224558.2362728-12-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200107224558.2362728-12-jhubbard@nvidia.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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 Tue, Jan 07, 2020 at 02:45:47PM -0800, John Hubbard wrote: > Introduce pin_user_pages*() variations of get_user_pages*() calls, > and also pin_longterm_pages*() variations. > > For now, these are placeholder calls, until the various call sites > are converted to use the correct get_user_pages*() or > pin_user_pages*() API. What do the pure placeholders buy us? The API itself looks ok, but until it actually is properly implemented it doesn't help at all, and we've had all kinds of bad experiences with these sorts of stub APIs.