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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 6050BC2D0EB for ; Sun, 29 Mar 2020 11:35:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 37E62206DB for ; Sun, 29 Mar 2020 11:35:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TzvY4+lT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728213AbgC2LfC (ORCPT ); Sun, 29 Mar 2020 07:35:02 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:46485 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728108AbgC2LfB (ORCPT ); Sun, 29 Mar 2020 07:35:01 -0400 Received: by mail-pl1-f195.google.com with SMTP id s23so5515780plq.13; Sun, 29 Mar 2020 04:35:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:date:from:to:cc:subject:references:mime-version :content-disposition:in-reply-to:user-agent; bh=3U2zGu5EljoEhInngF/MGy98drO8oW8eURU26m47lps=; b=TzvY4+lTJF2CwQProk5NFI9gwDe3ezuDrAgm0eiPalqwD0YZphnZjL1mhD1irNIfCu OQ+CXZHVbnkWSsfHL4LbXFzXDdZ9y3VQLtXa4V6NSW7ro/lmCpgvYxENt1PAx6ikmSeA vTpxzX7VItnu+O8XxhjWxh1aPf4laQZlAPtBnxPhpMXiTeBOyfY4TrUXiUdvX8JG9l2o pRCxJTM3Fd5THks2AAa3AyYv0GQfszgzQq4LCIRXqrHzF0aLYaPLG46CCJ99o74Q6Az1 C2s+dQdE/Siltzp4E7pz3/ds8zZFNn79z6/fXy2EsUq1HjE9jwd/ItKyJcoF0gt5lfQ6 bY3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:date:from:to:cc:subject:references :mime-version:content-disposition:in-reply-to:user-agent; bh=3U2zGu5EljoEhInngF/MGy98drO8oW8eURU26m47lps=; b=tNqdAoeBIeunsqYwN/6feaePyBA8r7c9TpAdYSwxTeZxWnlNt765EXiIHBNNz19EaI FJUEzTtChe2YOqUHDstzHIkCb/hQWpz7nRyjx441++bWJ18ZC0VTbiX8CU7K/w34xo2s 0MgLGxaEY6AJQw04an+4JzkHs+zAZHGC460n8UErygWHPMVxUIGSDoOgUmHae4y/dAPx 7ZRgfyjDWwhvtAdHldSLq8smO9nEe24WMJMPJBVrBhFlDYUBEfJP8vSUefAyqFrZU/IO 1jbWqRGIg0Z7yLB5HTuzgyJALGcdYcptgh2sYQJ1e/tR/mhQY5sS6oJTS8OMyghHMVbf Go8w== X-Gm-Message-State: ANhLgQ21x73j59tvArUJqTwvUvq7ly3ndI8aSpblI4H6jyzmVgJr8srP mW9MmoYARxrnabPhvhGxq5g= X-Google-Smtp-Source: ADFU+vtPceFIaWh3aJr0XVdTwVl7niibGUIx3WXzqSISGf9LEkmeNM+MRNqbmWde7Ju8vSNiwXqfdQ== X-Received: by 2002:a17:902:449:: with SMTP id 67mr7611883ple.339.1585481700644; Sun, 29 Mar 2020 04:35:00 -0700 (PDT) Received: from SARKAR ([2401:4900:331f:aaac:2ce4:2642:30f:c482]) by smtp.gmail.com with ESMTPSA id w127sm7909245pfb.70.2020.03.29.04.34.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 29 Mar 2020 04:34:59 -0700 (PDT) Message-ID: <5e8087e3.1c69fb81.13d97.448d@mx.google.com> X-Google-Original-Message-ID: <20200329113451.GB8353@rohitsarkar5398@gmail.com> Date: Sun, 29 Mar 2020 17:04:51 +0530 From: Rohit Sarkar To: Jonathan Cameron Cc: linux-iio@vger.kernel.org, dragos.bogdan@analog.com, Lars-Peter Clausen , Michael Hennerich , Stefan Popa , Hartmut Knaack , Peter Meerwald-Stadler , linux-kernel@vger.kernel.org, "Ardelean, Alexandru" , zhong jiang Subject: Re: [PATCH 0/2] use DEFINE_DEBUGFS_ATTRIBUTE instead of DEFINE_SIMPLE_ATTRIBUTE References: <20200328063456.24012-1-rohitsarkar5398@gmail.com> <20200329103818.2fce9529@archlinux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200329103818.2fce9529@archlinux> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 29, 2020 at 10:38:18AM +0100, Jonathan Cameron wrote: > On Sat, 28 Mar 2020 12:04:53 +0530 > Rohit Sarkar wrote: > > > The debugfs_create_file_unsafe method does not protect the fops given to > > it from file removal. It must be used with DEFINE_DEBUGFS_ATTRIBUTE > > which makes the fops aware of the file lifetime. > > > > Further using DEFINE_DEBUGFS_ATTRIBUTE along with > > debugfs_create_file_unsafe significantly reduces the overhead introduced by > > debugfs_create_file which creates a lifetime managing proxy around each > > fops handed in. Refer [1] for more on this. > > > > Fixes the following warnings reported by coccinelle: > > drivers/iio/imu//adis16460.c:126:0-23: WARNING: adis16460_flash_count_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > drivers/iio/imu//adis16460.c:108:0-23: WARNING: adis16460_product_id_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > drivers/iio/imu//adis16460.c:90:0-23: WARNING: adis16460_serial_number_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > drivers/iio/imu//adis16400.c:278:0-23: WARNING: adis16400_flash_count_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > drivers/iio/imu//adis16400.c:261:0-23: WARNING: adis16400_product_id_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > > > [1]: https://lists.gt.net/linux/kernel/2369498 > > > > Rohit Sarkar (2): > > iio: imu: adis16400: use DEFINE_DEBUGFS_ATTRIBUTE instead of > > DEFINE_SIMPLE_ATTRIBUTE > > iio: imu: adis16460: use DEFINE_DEBUGFS_ATTRIBUTE instead of > > DEFINE_SIMPLE_ATTRIBUTE > > > > drivers/iio/imu/adis16400.c | 4 ++-- > > drivers/iio/imu/adis16460.c | 6 +++--- > > 2 files changed, 5 insertions(+), 5 deletions(-) > > > Hi Rohit, Hey, > You've opened a can of worms with this one. There as a previous series > posted doing exactly this change back in 2019 by Zhong Jiang (cc'd) > > At the time I did a bit of looking into why this had been universally taken > up cross tree and turned out there are some potential issues. > > Alexandru added it to the list of things to test, but I guess it got > buried under other work and is still outstanding. > > https://lkml.org/lkml/2019/10/30/144 Acc. to the patch by Zhong this change kind of comes off as a cosmetic change as in the commit message he mentions "it is more clear". But there is certainly more to it than that: In the current scenario since we are using debugfs_create_file_unsafe the file has no protection whatsoever against removal. > Has Greg KH raising the point that file reference counting is changed (as you > mention) but that can cause subtle bugs. It 'might' be fine but is > definitely one that needs a tested-by from someone with the hardware. Sure that makes sense. > Jonathan Thanks, Rohit