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=-3.6 required=3.0 tests=BAYES_00,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 760F2C433ED for ; Mon, 10 May 2021 07:31:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F088C6143B for ; Mon, 10 May 2021 07:31:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F088C6143B 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 7978A6B0074; Mon, 10 May 2021 03:31:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7466C6B0075; Mon, 10 May 2021 03:31:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5E7A86B0078; Mon, 10 May 2021 03:31:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0143.hostedemail.com [216.40.44.143]) by kanga.kvack.org (Postfix) with ESMTP id 42D376B0074 for ; Mon, 10 May 2021 03:31:09 -0400 (EDT) Received: from smtpin33.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id EF611180ACF14 for ; Mon, 10 May 2021 07:31:08 +0000 (UTC) X-FDA: 78124500216.33.0E455F5 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf29.hostedemail.com (Postfix) with ESMTP id 2448CFE for ; Mon, 10 May 2021 07:31:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=RlPDTnrGP7VrkHHDZaeu5siASFXrL/7DV46d02KfOg8=; b=jVtYg1DpIhoMALo/8L1gTQX3ww 71nqSsTYByFChENtDDk7rl0AnbqCNYwo4kIyhxfdTGMVo2WSUaokSu6XHznVNC+zNG6w1+ZT7teAE U3xD//EkLHc4hnRNpZgrlDLhKr0c4uniH4OXlSCvuWDEqpbXAyJEuvBrmJwwjpntITYYjTHgWxP8+ TEhIsYdtK717BX+ucCD6EA1Ro67VHN9V61suNwsknLSPRw3z/gYot7uhl/qDZsHvzb9XvRvJ3WxY7 MYKLsyXSwII3NUgCBauC/Y3gs/9XnATB/PvFMAq+mU7jEsLMIynM0ji0AW3may0sqatghH7sRC3gx nZxczo9Q==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lg0M8-005oIH-AU; Mon, 10 May 2021 07:29:37 +0000 Date: Mon, 10 May 2021 08:29:32 +0100 From: Christoph Hellwig To: Daniel Vetter Cc: Linus Torvalds , Tomasz Figa , Marek Szyprowski , Mauro Carvalho Chehab , DRI Development , LKML , Linux-MM , Linux ARM , Linux Media Mailing List , linux-samsung-soc Subject: Re: [PULL] topic/iomem-mmap-vs-gup Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=jVtYg1Dp; dmarc=none; spf=none (imf29.hostedemail.com: domain of BATV@casper.srs.infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=BATV@casper.srs.infradead.org X-Stat-Signature: 9qnjdk966ipkkkmsre6qappsa7suaamc X-Rspamd-Queue-Id: 2448CFE X-Rspamd-Server: rspam05 Received-SPF: none (casper.srs.infradead.org>: No applicable sender policy available) receiver=imf29; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620631862-69447 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, May 10, 2021 at 09:16:58AM +0200, Daniel Vetter wrote: > > End result: not pulling it, unless somebody can explain to me in small > > words why I'm wrong and have the mental capacity of a damaged rodent. > > No rodents I think, just more backstory of how this all fits. tldr; > pin_user_pages is the only safe use of this vb2 userptr thing. Yes, which is why I advocate for just ripping the follow_pfn path out entirely. It could have been used for crazy ad dangerous peer to peer transfers outside of any infrastructure making it safe, or for pre-CMA kernel memory carveouts for lage contiguous memory allocations (which are pretty broken by design as well). So IMHO the only sensible thing is to remove this cruft entirely, and if it breaks a currently working setup (which I think is unlikely) we'll have to make sure it can work the proper way.