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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 4925DC04E53 for ; Wed, 15 May 2019 16:12:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B75420815 for ; Wed, 15 May 2019 16:12:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726978AbfEOQMd (ORCPT ); Wed, 15 May 2019 12:12:33 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:60714 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726292AbfEOQMc (ORCPT ); Wed, 15 May 2019 12:12:32 -0400 Received: from [IPv6:2804:431:9719:d573:a076:d1fd:3417:b195] (unknown [IPv6:2804:431:9719:d573:a076:d1fd:3417:b195]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: koike) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 3FCAB28355B; Wed, 15 May 2019 17:12:28 +0100 (BST) Subject: Re: dm ioctl: fix hang in early create error condition To: Mike Snitzer Cc: dm-devel@redhat.com, kernel@collabora.com, linux-kernel@vger.kernel.org, Alasdair Kergon References: <20190513192530.1167-1-helen.koike@collabora.com> <20190514013716.GA10260@lobo> From: Helen Koike Openpgp: preference=signencrypt Autocrypt: addr=helen.koike@collabora.com; keydata= mQINBFmOMD4BEADb2nC8Oeyvklh+ataw2u/3mrl+hIHL4WSWtii4VxCapl9+zILuxFDrxw1p XgF3cfx7g9taWBrmLE9VEPwJA6MxaVnQuDL3GXxTxO/gqnOFgT3jT+skAt6qMvoWnhgurMGH wRaA3dO4cFrDlLsZIdDywTYcy7V2bou81ItR5Ed6c5UVX7uTTzeiD/tUi8oIf0XN4takyFuV 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+vPsD+TSVHc9m/YWrOiYDnZn6aO0Uk1Zv/m9+BBkWAwsreLJ/evn3SsJV1omNBTITG+uxXcf JkgmmesIAw8mpI6EeLmReUJLasz8QkzhZIC7t5rGlQI94GQG3Jg2dC+kpaGWOaT5G4FVMcBj iR1nXfMxENVYnM5ag7mBZyD/kru5W1Uj34L6AFaDMXFPwedSCpzzqUiHb0f+nYkfOodf5xy0 46+3THy/NUS/ZZp/rI4F7Y77+MQPVg7vARfHHX1AxYUKfRVW5j88QUB70txn8Vgi1tDrOr4J eD+xr0CvIGa5lKqgQacQtGkpOpJ8zY4ObSvpNubey/qYUE3DCXD0n2Xxk4muTvqlkFpOYA== Message-ID: <78dda04b-925f-49eb-f88a-6d940bcc4754@collabora.com> Date: Wed, 15 May 2019 13:12:03 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190514013716.GA10260@lobo> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 5/13/19 10:37 PM, Mike Snitzer wrote: > On Mon, May 13 2019 at 3:25P -0400, > Helen Koike wrote: > >> The dm_early_create() function (which deals with "dm-mod.create=" kernel >> command line option) calls dm_hash_insert() who gets an extra reference >> to the md object. >> >> In case of failure, this reference wasn't being released, causing >> dm_destroy() to hang, thus hanging the whole boot process. >> >> Fix this by calling __hash_remove() in the error path. >> >> Fixes: 6bbc923dfcf57d ("dm: add support to directly boot to a mapped device") >> Cc: stable@vger.kernel.org >> Signed-off-by: Helen Koike >> >> --- >> Hi, >> >> I tested this patch by adding a new test case in the following test >> script: >> >> https://gitlab.collabora.com/koike/dm-cmdline-test/commit/d2d7a0ee4a49931cdb59f08a837b516c2d5d743d >> >> This test was failing, but with this patch it works correctly. >> >> Thanks >> Helen > > Thanks for the patch but I'd prefer the following simpler fix. What do > you think? > > That said, I can provide a follow-on patch (inspired by the patch you > provided) that encourages more code sharing between dm_early_create() > and dev_create() by factoring out __dev_create(). Sounds great. > > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c > index c740153b4e52..0eb0b462c736 100644 > --- a/drivers/md/dm-ioctl.c > +++ b/drivers/md/dm-ioctl.c > @@ -2117,6 +2117,7 @@ int __init dm_early_create(struct dm_ioctl *dmi, > err_destroy_table: > dm_table_destroy(t); > err_destroy_dm: > + (void) __hash_remove(__find_device_hash_cell(dmi)); > dm_put(md); > dm_destroy(md); > return r; > This doesn't really work for two reasons: 1) __find_device_hash_cell() requires a mutual exclusivity between name, uuid and dev. In dm_early_create(), dmi can have more then one of these. 2) I can fix (1) by calling __get_name_cell(), as the name is mandatory anyway, but this function also grabs another reference to the md object, so I need to add an extra dm_put(md) there: err_destroy_table: dm_table_destroy(t); +err_hash_remove: + (void) __hash_remove(__get_name_cell(dmi->name)); + dm_put(md); err_destroy_dm: dm_put(md); dm_destroy(md); What do you think? Is this ok? Thanks Helen