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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 42C38C37122 for ; Tue, 22 Jan 2019 00:29:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1732121721 for ; Tue, 22 Jan 2019 00:29:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726724AbfAVA3q (ORCPT ); Mon, 21 Jan 2019 19:29:46 -0500 Received: from mga06.intel.com ([134.134.136.31]:21558 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725962AbfAVA3q (ORCPT ); Mon, 21 Jan 2019 19:29:46 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jan 2019 16:29:45 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,504,1539673200"; d="scan'208";a="127777931" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.37]) by orsmga002.jf.intel.com with ESMTP; 21 Jan 2019 16:29:44 -0800 Date: Tue, 22 Jan 2019 08:29:16 +0800 From: Wei Yang To: Wei Yang Cc: Dan Williams , linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] libnvdimm: Clarify nd_pfn_init() flow Message-ID: <20190122002915.GA5984@richard> Reply-To: Wei Yang References: <154785884329.2202034.3295476681016958230.stgit@dwillia2-desk3.amr.corp.intel.com> <20190121075102.GA3758@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190121075102.GA3758@richard> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 21, 2019 at 03:51:02PM +0800, Wei Yang wrote: >On Fri, Jan 18, 2019 at 04:47:23PM -0800, Dan Williams wrote: >>In recent days, 2 engineers, including the original author of >>nd_pfn_init(), overlooked the internal call to nd_pfn_validate() and the >>implications to memory allocation. >> >>Clarify this situation to help anyone that reads through this code in >>the future. >> >>Reported-by: Wei Yang >>Signed-off-by: Dan Williams >>--- >> drivers/nvdimm/btt_devs.c | 5 +++++ >> drivers/nvdimm/dax_devs.c | 5 +++++ >> drivers/nvdimm/pfn_devs.c | 21 +++++++++++++++++++++ >> 3 files changed, 31 insertions(+) >> >>diff --git a/drivers/nvdimm/btt_devs.c b/drivers/nvdimm/btt_devs.c >>index 795ad4ff35ca..e0a6f2491e57 100644 >>--- a/drivers/nvdimm/btt_devs.c >>+++ b/drivers/nvdimm/btt_devs.c >>@@ -354,6 +354,11 @@ int nd_btt_probe(struct device *dev, struct nd_namespace_common *ndns) >> put_device(btt_dev); >> } >> >>+ /* >>+ * Successful probe indicates to the caller that an nd_btt >>+ * personality device has been registered and the caller can >>+ * fail the probe of the baseline namespace device. >>+ */ >> return rc; >> } >> EXPORT_SYMBOL(nd_btt_probe); >>diff --git a/drivers/nvdimm/dax_devs.c b/drivers/nvdimm/dax_devs.c >>index 0453f49dc708..65010d955fa7 100644 >>--- a/drivers/nvdimm/dax_devs.c >>+++ b/drivers/nvdimm/dax_devs.c >>@@ -136,6 +136,11 @@ int nd_dax_probe(struct device *dev, struct nd_namespace_common *ndns) >> } else >> __nd_device_register(dax_dev); >> >>+ /* >>+ * Successful probe indicates to the caller that a device-dax >>+ * personality device has been registered and the caller can >>+ * fail the probe of the baseline namespace device. >>+ */ >> return rc; >> } >> EXPORT_SYMBOL(nd_dax_probe); >>diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c >>index 6f22272e8d80..a8783b5a76ba 100644 >>--- a/drivers/nvdimm/pfn_devs.c >>+++ b/drivers/nvdimm/pfn_devs.c >>@@ -576,6 +576,11 @@ int nd_pfn_probe(struct device *dev, struct nd_namespace_common *ndns) >> } else >> __nd_device_register(pfn_dev); >> >>+ /* >>+ * Successful probe indicates to the caller that an nd_pfn >>+ * personality device has been registered and the caller can >>+ * fail the probe of the baseline namespace device. >>+ */ >> return rc; >> } >> EXPORT_SYMBOL(nd_pfn_probe); >>@@ -706,6 +711,22 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) >> sig = DAX_SIG; >> else >> sig = PFN_SIG; >>+ >>+ /* >>+ * Check for an existing 'pfn' superblock before writing a new >>+ * one. The intended flow is that on the first probe of an >>+ * nd_{pfn,dax} device the superblock is calculated and written >>+ * to the namespace. In this case nd_pfn_validate() returns >>+ * -ENODEV because no valid superblock exists currently. >>+ * >>+ * On subsequent probes nd_pfn_validate() will find a valid >>+ * superblock and return 0. >>+ * >>+ * If an assumption of the superblock has been violated, like a >>+ * change to the physical alignment of the namespace, >>+ * nd_pfn_validate() will return an error other than -ENODEV to >>+ * fail probing. >>+ */ > >Let me reply in this thread. Sorry for my poor understand, I don't get it >clearly now. > >To be honest, the structure is a little bit complicated, if my understanding >is not correct, please forgive my poor understand. > >Below is a code flow. To simply analysis, I setup kernel parameter memmap to >emulate, and configure one namespace to mode devdax. So that we would have the >same root for code flow. > >Let's start with nd_region_driver: > > nd_region_probe > nd_region_register_namespaces > create_namespaces > nd_region->btt_seed = nd_btt_create(nd_region); > nd_region->pfn_seed = nd_pfn_create(nd_region); > nd_region->dax_seed = nd_dax_create(nd_region); May I ask a question about the purpose to create these three device here? I see nd_pfn_create() doesn't allocate pfn_sb here, and the probe on these devices failed. Confused why we need these three devices. -- Wei Yang Help you, Help me