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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 44974C4338F for ; Fri, 20 Aug 2021 04:56:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B21DA60FE7 for ; Fri, 20 Aug 2021 04:56:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B21DA60FE7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 50FB76B0071; Fri, 20 Aug 2021 00:56:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4979E6B0072; Fri, 20 Aug 2021 00:56:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 35FFA8D0001; Fri, 20 Aug 2021 00:56:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0251.hostedemail.com [216.40.44.251]) by kanga.kvack.org (Postfix) with ESMTP id 188146B0071 for ; Fri, 20 Aug 2021 00:56:31 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id AA7EF1817B07D for ; Fri, 20 Aug 2021 04:56:30 +0000 (UTC) X-FDA: 78494248140.14.2655BAC Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf12.hostedemail.com (Postfix) with ESMTP id 53D2710000A5 for ; Fri, 20 Aug 2021 04:56:30 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id AD1156736F; Fri, 20 Aug 2021 06:56:27 +0200 (CEST) Date: Fri, 20 Aug 2021 06:56:27 +0200 From: Christoph Hellwig To: Ralph Campbell Cc: Felix Kuehling , Alex Sierra , akpm@linux-foundation.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jgg@nvidia.com, jglisse@redhat.com Subject: Re: [PATCH v6 02/13] mm: remove extra ZONE_DEVICE struct page refcount Message-ID: <20210820045627.GA27083@lst.de> References: <20210813063150.2938-1-alex.sierra@amd.com> <20210813063150.2938-3-alex.sierra@amd.com> <7b821150-af18-f786-e419-ec245b8cfb1e@nvidia.com> <393e9815-838d-5fe6-d6ab-bfe7b543fef6@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Authentication-Results: imf12.hostedemail.com; dkim=none; spf=none (imf12.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de; dmarc=none X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 53D2710000A5 X-Stat-Signature: 4ojiu8e1fmkq1j974xb3jtw17u3gid74 X-HE-Tag: 1629435390-98771 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000028, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 18, 2021 at 12:28:30PM -0700, Ralph Campbell wrote: > Did you test on a system without CONFIG_ARCH_HAS_PTE_SPECIAL defined? > In that case, mmap() of a DAX device will call insert_page() which calls > get_page() which would trigger VM_BUG_ON_PAGE(). __vm_insert_mixed still ends up calling insert_pfn for the !CASE_ARCH_HAS_PTE_SPECIAL if pfn_t_devmap() is true, which it should be for DAX. (and as said in my other mail, I suspect we should disallow that case anyway, as no one can test it in practice).