From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751665AbeCQJpx (ORCPT ); Sat, 17 Mar 2018 05:45:53 -0400 Received: from mail-io0-f196.google.com ([209.85.223.196]:37402 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbeCQJpv (ORCPT ); Sat, 17 Mar 2018 05:45:51 -0400 X-Google-Smtp-Source: AG47ELuJ1sOb0qMVGUYdr8pyUPZ/z+CykFyLBoDvSoLq1XYvZmOhYJtvD6qOTX5bv6xy3REdyea0Cw== Subject: Re: [PATCH 1/2] mtd: use put_device() if device_register fail To: Boris Brezillon References: <39c4af723ea37cd05976a17cb9c1fbc975496ffd.1520592440.git.arvind.yadav.cs@gmail.com> <20180314153600.458c0fe4@bbrezillon> Cc: dwmw2@infradead.org, computersforpeace@gmail.com, boris.brezillon@free-electrons.com, marek.vasut@gmail.com, richard@nod.at, cyrille.pitchen@wedev4u.fr, dedekind1@gmail.com, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org From: arvindY Message-ID: <5AACE3C9.9090602@gmail.com> Date: Sat, 17 Mar 2018 15:15:45 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20180314153600.458c0fe4@bbrezillon> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 14 March 2018 08:06 PM, Boris Brezillon wrote: > On Fri, 9 Mar 2018 16:20:48 +0530 > Arvind Yadav wrote: > >> if device_register() returned an error! Always use put_device() >> to give up the reference initialized. >> >> Signed-off-by: Arvind Yadav >> --- >> drivers/mtd/mtdcore.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c >> index 28553c8..4d77ca2 100644 >> --- a/drivers/mtd/mtdcore.c >> +++ b/drivers/mtd/mtdcore.c >> @@ -586,6 +586,7 @@ int add_mtd_device(struct mtd_info *mtd) >> return 0; >> >> fail_added: >> + put_device(&mtd->dev); > Not sure this is a good idea: the put_device() call will trigger > an mtd_devtype->release(), which will in turn call device_destroy() on > something that does not exist yet. Not sure if this is a real problem, > but it does not look like the right thing to do. > yes, you are correct. No need to call put_device(). which can cause other problem. >> of_node_put(mtd_get_of_node(mtd)); > You're referencing an object that is supposed to have been > freed/released by the put_device() call. Again, it's not really a > problem because in our case ->release() does not free the mtd object > (as is usually done in other parts of the kernel), but it still looks > wrong. It's probably better to move the of_node_put() and the below > idr_remove() call in the ->release() hook if you want to use > put_device(). > >> idr_remove(&mtd_idr, i); Sure, we can move put_device() below this. But need to check how we can add hook in release. > >> fail_locked: > > ~arvind