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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 8D912C3A5A1 for ; Thu, 22 Aug 2019 18:56:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A2B8233A2 for ; Thu, 22 Aug 2019 18:56:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731765AbfHVS4C (ORCPT ); Thu, 22 Aug 2019 14:56:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38108 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726142AbfHVS4B (ORCPT ); Thu, 22 Aug 2019 14:56:01 -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 6B915300180E; Thu, 22 Aug 2019 18:56:01 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C5F58600CD; Thu, 22 Aug 2019 18:56:00 +0000 (UTC) From: Jeff Moyer To: Jia He Cc: Dan Williams , Vishal Verma , linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org Subject: Re: [PATCH 2/2] drivers/dax/kmem: give a warning if CONFIG_DEV_DAX_PMEM_COMPAT is enabled References: <20190816111844.87442-1-justin.he@arm.com> <20190816111844.87442-3-justin.he@arm.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Thu, 22 Aug 2019 14:55:59 -0400 In-Reply-To: <20190816111844.87442-3-justin.he@arm.com> (Jia He's message of "Fri, 16 Aug 2019 19:18:44 +0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain 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 [10.5.110.40]); Thu, 22 Aug 2019 18:56:01 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jia He writes: > commit c221c0b0308f ("device-dax: "Hotplug" persistent memory for use > like normal RAM") helps to add persistent memory as normal RAM blocks. > But this driver doesn't work if CONFIG_DEV_DAX_PMEM_COMPAT is enabled. > > Here is the debugging call trace when CONFIG_DEV_DAX_PMEM_COMPAT is > enabled. > [ 4.443730] devm_memremap_pages+0x4b9/0x540 > [ 4.443733] dev_dax_probe+0x112/0x220 [device_dax] > [ 4.443735] dax_pmem_compat_probe+0x58/0x92 [dax_pmem_compat] > [ 4.443737] nvdimm_bus_probe+0x6b/0x150 > [ 4.443739] really_probe+0xf5/0x3d0 > [ 4.443740] driver_probe_device+0x11b/0x130 > [ 4.443741] device_driver_attach+0x58/0x60 > [ 4.443742] __driver_attach+0xa3/0x140 > > Then the dax0.0 device will be registered as "nd" bus instead of > "dax" bus. This causes the error as follows: > root@ubuntu:~# echo dax0.0 > /sys/bus/dax/drivers/device_dax/unbind > -bash: echo: write error: No such device > > This gives a warning to notify the user. > > Signed-off-by: Jia He > --- > drivers/dax/kmem.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index ad62d551d94e..b77f0e880598 100644 > --- a/drivers/dax/kmem.c > +++ b/drivers/dax/kmem.c > @@ -93,6 +93,11 @@ static struct dax_device_driver device_dax_kmem_driver = { > > static int __init dax_kmem_init(void) > { > + if (IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)) { > + pr_warn("CONFIG_DEV_DAX_PMEM_COMPAT is not compatible\n"); > + pr_warn("kmem dax driver might not be workable\n"); > + } > + > return dax_driver_register(&device_dax_kmem_driver); > } This logic is wrong (and the error message is *very* confusing). You can have the driver configured, but not loaded. In that case, the kmem driver will load and work properly. When using daxctl to online memory, you already get the following message: libdaxctl: daxctl_dev_disable: dax0.0: error: device model is dax-class That's still not very helpful. It would be better if the message suggested a fix (like using migrate-device-model). Vishal? Cheers, Jeff