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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2503C433F5 for ; Thu, 4 Nov 2021 08:37:13 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 650FD6112D for ; Thu, 4 Nov 2021 08:37:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 650FD6112D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=redhat.com Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-408-gnnCW_FBOtuCPtToECKUiA-1; Thu, 04 Nov 2021 04:37:09 -0400 X-MC-Unique: gnnCW_FBOtuCPtToECKUiA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B77E5100C619; Thu, 4 Nov 2021 08:37:04 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7F7805C1D0; Thu, 4 Nov 2021 08:37:04 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id DF5644A703; Thu, 4 Nov 2021 08:37:03 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 1A48b1Tg015102 for ; Thu, 4 Nov 2021 04:37:02 -0400 Received: by smtp.corp.redhat.com (Postfix) id 04AB640CFD11; Thu, 4 Nov 2021 08:37:01 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast04.extmail.prod.ext.rdu2.redhat.com [10.11.55.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F315B40CFD0A for ; Thu, 4 Nov 2021 08:37:00 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D7FD41161A85 for ; Thu, 4 Nov 2021 08:37:00 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-376-Y4fiQCsOPb-RTWcoSCImiA-1; Thu, 04 Nov 2021 04:36:59 -0400 X-MC-Unique: Y4fiQCsOPb-RTWcoSCImiA-1 Received: from hch by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1miYEp-008Jwb-Cd; Thu, 04 Nov 2021 08:36:47 +0000 Date: Thu, 4 Nov 2021 01:36:47 -0700 From: Christoph Hellwig To: Dan Williams Message-ID: References: <20211021001059.438843-1-jane.chu@oracle.com> <2102a2e6-c543-2557-28a2-8b0bdc470855@oracle.com> <20211028002451.GB2237511@magnolia> MIME-Version: 1.0 In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 X-loop: dm-devel@redhat.com Cc: Jane Chu , "nvdimm@lists.linux.dev" , "dave.jiang@intel.com" , "snitzer@redhat.com" , "vishal.l.verma@intel.com" , "david@fromorbit.com" , "linux-kernel@vger.kernel.org" , "willy@infradead.org" , Christoph Hellwig , "dm-devel@redhat.com" , "vgoyal@redhat.com" , "Darrick J. Wong" , "linux-fsdevel@vger.kernel.org" , "ira.weiny@intel.com" , "linux-xfs@vger.kernel.org" , "agk@redhat.com" Subject: Re: [dm-devel] [PATCH 0/6] dax poison recovery with RWF_RECOVERY_DATA flag X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Wed, Nov 03, 2021 at 11:21:39PM -0700, Dan Williams wrote: > The concern I have with dax_clear_poison() is that it precludes atomic > error clearing. atomic as in clear poison and write the actual data? Yes, that would be useful, but it is not how the Intel pmem support actually works, right? > Also, as Boris and I discussed, poisoned pages should > be marked NP (not present) rather than UC (uncacheable) [1]. This would not really have an affect on the series, right? But yes, that seems like the right thing to do. > With > those 2 properties combined I think that wants a custom pmem fault > handler that knows how to carefully write to pmem pages with poison > present, rather than an additional explicit dax-operation. That also > meets Christoph's requirement of "works with the intended direct > memory map use case". So we have 3 kinds of accesses to DAX memory: (1) user space mmap direct access. (2) iov_iter based access (could be from kernel or userspace) (3) open coded kernel access using ->direct_access One thing I noticed: (2) could also work with kernel memory or pages, but that doesn't use MC safe access. Which seems like a major independent of this discussion. I suspect all kernel access could work fine with a copy_mc_to_kernel helper as long as everyone actually uses it, which will cover the missing required bits of (2) and (3) together with something like the ->clear_poison series from Jane. We just need to think hard what we want to do for userspace mmap access. -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel