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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12C07C433EF for ; Fri, 15 Jul 2022 15:57:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229913AbiGOP5p (ORCPT ); Fri, 15 Jul 2022 11:57:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229510AbiGOP5n (ORCPT ); Fri, 15 Jul 2022 11:57:43 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1B25763904 for ; Fri, 15 Jul 2022 08:57:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657900662; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/FdZSaJ6nYpAHiWDAVZdlLoPRtdepjpdp6VwK6oqQrM=; b=M2m9fFnVhCUXouJuvSh1+0y696MV5z6RAlUH5wwSrmQLpJhiR3IxS9EBdOzslnZ8MARcdQ LSsO5/Bo9ZsxB0CwCZb96wMj+ZzcPGYCcnNafzN4L9yzhDGVVnVQslKCh0A3ffC5mH8t2e hi8lFUADwtiCSLKoZwkqTdNC9UljUOQ= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-490-IlLMWm90MDWU3IvRpObP7g-1; Fri, 15 Jul 2022 11:57:38 -0400 X-MC-Unique: IlLMWm90MDWU3IvRpObP7g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7B7EC299E76B; Fri, 15 Jul 2022 15:57:37 +0000 (UTC) Received: from lorien.usersys.redhat.com (unknown [10.39.193.130]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9ADC91121314; Fri, 15 Jul 2022 15:57:34 +0000 (UTC) Date: Fri, 15 Jul 2022 11:57:30 -0400 From: Phil Auld To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, "Rafael J . Wysocki" , Barry Song <21cnbao@gmail.com>, Tian Tao , Yury Norov , stable@vger.kernel.org Subject: Re: [PATCH v5] drivers/base: fix userspace break from using bin_attributes for cpumap and cpulist Message-ID: References: <20220715134924.3466194-1-pauld@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 15, 2022 at 05:37:13PM +0200 Greg Kroah-Hartman wrote: > On Fri, Jul 15, 2022 at 09:49:24AM -0400, Phil Auld wrote: > > Using bin_attributes with a 0 size causes fstat and friends to return that > > 0 size. This breaks userspace code that retrieves the size before reading > > the file. Rather than reverting 75bd50fa841 ("drivers/base/node.c: use > > bin_attribute to break the size limitation of cpumap ABI") let's put in a > > size value at compile time. > > > > For cpulist the maximum size is on the order of > > NR_CPUS * (ceil(log10(NR_CPUS)) + 1)/2 > > > > which for 8192 is 20480 (8192 * 5)/2. In order to get near that you'd need > > a system with every other CPU on one node. For example: (0,2,4,8, ... ). > > To simplify the math and support larger NR_CPUS in the future we are using > > (NR_CPUS * 7)/2. We also set it to a min of PAGE_SIZE to retain the older > > behavior for smaller NR_CPUS. > > > > The cpumap file the size works out to be NR_CPUS/4 + NR_CPUS/32 - 1 > > (or NR_CPUS * 9/32 - 1) including the ","s. > > > > Add a set of macros for these values to cpumask.h so they can be used in > > multiple places. Apply these to the handful of such files in > > drivers/base/topology.c as well as node.c. > > > > As an example, on an 80 cpu 4-node system (NR_CPUS == 8192): > > > > before: > > > > -r--r--r--. 1 root root 0 Jul 12 14:08 system/node/node0/cpulist > > -r--r--r--. 1 root root 0 Jul 11 17:25 system/node/node0/cpumap > > > > after: > > > > -r--r--r--. 1 root root 28672 Jul 13 11:32 system/node/node0/cpulist > > -r--r--r--. 1 root root 4096 Jul 13 11:31 system/node/node0/cpumap > > > > CONFIG_NR_CPUS = 16384 > > -r--r--r--. 1 root root 57344 Jul 13 14:03 system/node/node0/cpulist > > -r--r--r--. 1 root root 4607 Jul 13 14:02 system/node/node0/cpumap > > > > The actual number of cpus doesn't matter for the reported size since they > > are based on NR_CPUS. > > > > Fixes: 75bd50fa841 ("drivers/base/node.c: use bin_attribute to break the size limitation of cpumap ABI") > > Fixes: bb9ec13d156 ("topology: use bin_attribute to break the size limitation of cpumap ABI") > > Nit, use the full 12 characters otherwise our tools will complain. I'll > go fix it up by hand... > Erm, counting is hard... I thought I did have 12 :) > thanks for sticking with this. Thanks for the patience. Cheers, Phil > > greg k-h > --