From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:34052) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hIdas-0007k6-E6 for qemu-devel@nongnu.org; Mon, 22 Apr 2019 14:23:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hIdar-0007e9-5I for qemu-devel@nongnu.org; Mon, 22 Apr 2019 14:23:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52424) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hIdaq-0007cp-W6 for qemu-devel@nongnu.org; Mon, 22 Apr 2019 14:23:05 -0400 Date: Mon, 22 Apr 2019 15:22:55 -0300 From: Eduardo Habkost Message-ID: <20190422182255.GV25134@habkost.net> References: <20190422004849.26463-1-richardw.yang@linux.intel.com> <20190422083013-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190422083013-mutt-send-email-mst@kernel.org> Subject: Re: [Qemu-devel] [PATCH v14 0/2] support MAP_SYNC for memory-backend-file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Wei Yang , qemu-devel@nongnu.org, xiaoguangrong.eric@gmail.com, stefanha@redhat.com, pbonzini@redhat.com, pagupta@redhat.com, yu.c.zhang@linux.intel.com, imammedo@redhat.com, dan.j.williams@intel.com, yi.z.zhang@linux.intel.com On Mon, Apr 22, 2019 at 08:34:51AM -0400, Michael S. Tsirkin wrote: > On Mon, Apr 22, 2019 at 08:48:47AM +0800, Wei Yang wrote: > > Linux 4.15 introduces a new mmap flag MAP_SYNC, which can be used to > > guarantee the write persistence to mmap'ed files supporting DAX (e.g., > > files on ext4/xfs file system mounted with '-o dax'). > > > > A description of MAP_SYNC and MAP_SHARED_VALIDATE can be found at > > https://patchwork.kernel.org/patch/10028151/ > > > > In order to make sure that the file metadata is in sync after a fault > > while we are writing a shared DAX supporting backend files, this > > patch-set enables QEMU to use MAP_SYNC flag for memory-backend-dax-file. > > > > As the DAX vs DMA truncated issue was solved, we refined the code and > > send out this feature for the v5 version. > > > > We will pass MAP_SYNC to mmap(2); if MAP_SYNC is supported and > > 'share=on' & 'pmem=on'. > > Or QEMU will not pass this flag to mmap(2) > > OK this is in a good shape. As we are in freeze anyway, > there's still a bit more time to polish it. I have a couple of > suggestions: > > - squash docs in same patch with code, no need for two patches > - mmap errors are not silently ignored as the doc says, > a warning is produced Note that a warning is produced only if both share=on and pmem=on is specified. If using pmem=on without share=on, no warning is printed at all. I agree we could squash the docs in the same patch, but I don't want to prevent the code from being merged and require v15 to be sent just because we are still polishing the documentation. If there are no objections, I plan to apply this version of the series including the following fixup (just removing the word "silently"), and I suggest further improvements to be sent as follow up patches. diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index bcd1456e72..b531cacd35 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -159,8 +159,8 @@ If these conditions are not satisfied i.e. if either 'pmem' or 'share' are not set, if the backend file does not support DAX or if MAP_SYNC is not supported by the host kernel, write persistence is not guaranteed after a system crash. For compatibility reasons, these -conditions are silently ignored if not satisfied. Currently, no way -is provided to test for them. +conditions are ignored if not satisfied. Currently, no way is +provided to test for them. For more details, please reference mmap(2) man page: http://man7.org/linux/man-pages/man2/mmap.2.html. -- Eduardo 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=-5.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 D93B9C10F11 for ; Mon, 22 Apr 2019 18:24:57 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A60AB214AE for ; Mon, 22 Apr 2019 18:24:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A60AB214AE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:41008 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hIdce-0000H4-TL for qemu-devel@archiver.kernel.org; Mon, 22 Apr 2019 14:24:56 -0400 Received: from eggs.gnu.org ([209.51.188.92]:34052) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hIdas-0007k6-E6 for qemu-devel@nongnu.org; Mon, 22 Apr 2019 14:23:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hIdar-0007e9-5I for qemu-devel@nongnu.org; Mon, 22 Apr 2019 14:23:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52424) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hIdaq-0007cp-W6 for qemu-devel@nongnu.org; Mon, 22 Apr 2019 14:23:05 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D82F2C05683E; Mon, 22 Apr 2019 18:23:02 +0000 (UTC) Received: from localhost (ovpn-116-9.gru2.redhat.com [10.97.116.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8470A60141; Mon, 22 Apr 2019 18:22:56 +0000 (UTC) Date: Mon, 22 Apr 2019 15:22:55 -0300 From: Eduardo Habkost To: "Michael S. Tsirkin" Message-ID: <20190422182255.GV25134@habkost.net> References: <20190422004849.26463-1-richardw.yang@linux.intel.com> <20190422083013-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190422083013-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 22 Apr 2019 18:23:02 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v14 0/2] support MAP_SYNC for memory-backend-file X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pagupta@redhat.com, xiaoguangrong.eric@gmail.com, qemu-devel@nongnu.org, yi.z.zhang@linux.intel.com, yu.c.zhang@linux.intel.com, Wei Yang , stefanha@redhat.com, imammedo@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190422182255.F7MA5VFb7mQJ4pbbfuQxFSjKAmZcqPpwNNHixjUuLsc@z> On Mon, Apr 22, 2019 at 08:34:51AM -0400, Michael S. Tsirkin wrote: > On Mon, Apr 22, 2019 at 08:48:47AM +0800, Wei Yang wrote: > > Linux 4.15 introduces a new mmap flag MAP_SYNC, which can be used to > > guarantee the write persistence to mmap'ed files supporting DAX (e.g., > > files on ext4/xfs file system mounted with '-o dax'). > > > > A description of MAP_SYNC and MAP_SHARED_VALIDATE can be found at > > https://patchwork.kernel.org/patch/10028151/ > > > > In order to make sure that the file metadata is in sync after a fault > > while we are writing a shared DAX supporting backend files, this > > patch-set enables QEMU to use MAP_SYNC flag for memory-backend-dax-file. > > > > As the DAX vs DMA truncated issue was solved, we refined the code and > > send out this feature for the v5 version. > > > > We will pass MAP_SYNC to mmap(2); if MAP_SYNC is supported and > > 'share=on' & 'pmem=on'. > > Or QEMU will not pass this flag to mmap(2) > > OK this is in a good shape. As we are in freeze anyway, > there's still a bit more time to polish it. I have a couple of > suggestions: > > - squash docs in same patch with code, no need for two patches > - mmap errors are not silently ignored as the doc says, > a warning is produced Note that a warning is produced only if both share=on and pmem=on is specified. If using pmem=on without share=on, no warning is printed at all. I agree we could squash the docs in the same patch, but I don't want to prevent the code from being merged and require v15 to be sent just because we are still polishing the documentation. If there are no objections, I plan to apply this version of the series including the following fixup (just removing the word "silently"), and I suggest further improvements to be sent as follow up patches. diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index bcd1456e72..b531cacd35 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -159,8 +159,8 @@ If these conditions are not satisfied i.e. if either 'pmem' or 'share' are not set, if the backend file does not support DAX or if MAP_SYNC is not supported by the host kernel, write persistence is not guaranteed after a system crash. For compatibility reasons, these -conditions are silently ignored if not satisfied. Currently, no way -is provided to test for them. +conditions are ignored if not satisfied. Currently, no way is +provided to test for them. For more details, please reference mmap(2) man page: http://man7.org/linux/man-pages/man2/mmap.2.html. -- Eduardo