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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 74A22C433ED for ; Thu, 29 Apr 2021 15:46:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEB8C61447 for ; Thu, 29 Apr 2021 15:46:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240646AbhD2PrQ (ORCPT ); Thu, 29 Apr 2021 11:47:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:46084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232989AbhD2PrP (ORCPT ); Thu, 29 Apr 2021 11:47:15 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2FC3161418; Thu, 29 Apr 2021 15:46:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619711186; bh=/VKU8BHFV59c+saQPJazlJKeZ1egZHPlDGpRVTaqF18=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oo+Tooz5WEkT5vZmP5cFl0QHgzIRrbjTSH8T8DDJnqg6EJk2ooRGKe86Xp3CVQj0D kzwCVojGtFf4hs5GvKrAhXX/oU4ZjmI+TEFqWMDOYO75OkfBpd6uBhmmVMwR5aVbqz 1XGnYKH4qJHP+y+/Cb22Q3Yyih1kMZFFK3mF/kEg= Date: Thu, 29 Apr 2021 17:46:24 +0200 From: Greg KH To: Dave Hansen Cc: Tian Tao , corbet@lwn.net, song.bao.hua@hisilicon.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Peter Zijlstra , Valentin Schneider , Dave Hansen , Daniel Bristot de Oliveira Subject: Re: [PATCH 1/2] CPU, NUMA topology ABIs: clarify the overflow issue of sysfs pagebuf Message-ID: References: <1619679819-45256-1-git-send-email-tiantao6@hisilicon.com> <1619679819-45256-2-git-send-email-tiantao6@hisilicon.com> <146e051b-603c-a6d3-43d8-d083cf2c8119@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <146e051b-603c-a6d3-43d8-d083cf2c8119@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 29, 2021 at 07:21:13AM -0700, Dave Hansen wrote: > On 4/29/21 12:03 AM, Tian Tao wrote: > > diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node > > index 484fc04..82dfe64 100644 > > --- a/Documentation/ABI/stable/sysfs-devices-node > > +++ b/Documentation/ABI/stable/sysfs-devices-node > > @@ -47,7 +47,10 @@ What: /sys/devices/system/node/nodeX/cpulist > > Date: October 2002 > > Contact: Linux Memory Management list > > Description: > > - The CPUs associated to the node. > > + The CPUs associated to the node. The format is like 0-3, > > + 8-11, 14,17. maximum size is PAGE_SIZE, so the tail > > + of the string will be trimmed while its size is larger > > + than PAGE_SIZE. > > I think it's pretty arguable that truncating output on a real system is > an ABI break. Doing this would make the interface rather useless. > > Don't we need a real solution rather than throwing up our hands? > > Do we think >PAGE_SIZE data out of a sysfs file is a worse ABI break or > something? There is a real way to get > PAGE_SIZE out of a sysfs file. The LED developers had to do this when they ran into this same exact problem. Make it a binary sysfs file and promise to NEVER create such a file again in the future :) thanks, gre gk-h