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 A9E2AC43334 for ; Wed, 13 Jul 2022 13:46:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236032AbiGMNqA (ORCPT ); Wed, 13 Jul 2022 09:46:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231435AbiGMNpz (ORCPT ); Wed, 13 Jul 2022 09:45:55 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 739F4D41 for ; Wed, 13 Jul 2022 06:45:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657719950; 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: content-transfer-encoding:content-transfer-encoding; bh=FVrKbANdCl2uTQnD6+EajsfE/aId+mnisf9oBHzf9wQ=; b=fiBafRxLJvPLf9ovct9vGycGTUkZ6vh/5ErOw/nc+TjJPZRvs4MiXy4ADu2Z55AXW+8ztp SklEm/iaMwFHwToVRUfiK3ZDFIOP7uN5ag+jRYhFyEfu735xXAmT4tXsrFhzHTCNsTJx2G 127FLlTCJb5NiIyEgyrU3wjPrgwY4tY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-561-2o0gadQRPJyROXsSets1aw-1; Wed, 13 Jul 2022 09:45:47 -0400 X-MC-Unique: 2o0gadQRPJyROXsSets1aw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0667C85A581; Wed, 13 Jul 2022 13:45:47 +0000 (UTC) Received: from pauld.bos.com (dhcp-17-237.bos.redhat.com [10.18.17.237]) by smtp.corp.redhat.com (Postfix) with ESMTP id 85EF140CFD05; Wed, 13 Jul 2022 13:45:46 +0000 (UTC) From: Phil Auld To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , Barry Song <21cnbao@gmail.com>, Tian Tao Subject: [PATCH v2] drivers/base/node.c: fix userspace break from using bin_attributes for cpumap and cpulist Date: Wed, 13 Jul 2022 09:45:45 -0400 Message-Id: <20220713134545.1382367-1-pauld@redhat.com> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Use direct comparison and a worst-case maximum to ensure compile time constants. For cpulist the max is on the order of NR_CPUS * (ceil(log10(NR_CPUS)) + 1) which for 8192 is 40960 (8192 * 5). In order to get near that you'd need a system with every other CPU on one node or something similar. e.g. (0,2,4,... 1024,1026...). To simplify the math and support larger NR_CPUS we are using NR_CPUS * 6. We also set it to a min of PAGE_SIZE to retain the older behavior for smaller NR_CPUS. The cpumap file wants to be something like NR_CPUS/4 + NR_CPUS/32, for the ","s so for simplicity we are using NR_CPUS/2. On an 80 cpu 4-node sytem (NR_CPUS == 8192) before: -r--r--r--. 1 root root 0 Jul 12 14:08 /sys/devices/system/node/node0/cpulist -r--r--r--. 1 root root 0 Jul 11 17:25 /sys/devices/system/node/node0/cpumap after: -r--r--r--. 1 root root 49152 Jul 13 09:26 /sys/devices/system/node/node0/cpulist -r--r--r--. 1 root root 4096 Jul 13 09:24 /sys/devices/system/node/node0/cpumap Fixes: 75bd50fa841 ("drivers/base/node.c: use bin_attribute to break the size limitation of cpumap ABI") Cc: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" Signed-off-by: Phil Auld --- drivers/base/node.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/base/node.c b/drivers/base/node.c index 0ac6376ef7a1..3577f4eb4ac6 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -45,7 +45,7 @@ static inline ssize_t cpumap_read(struct file *file, struct kobject *kobj, return n; } -static BIN_ATTR_RO(cpumap, 0); +static BIN_ATTR_RO(cpumap, (((NR_CPUS>>1) > PAGE_SIZE) ? NR_CPUS >> 1 : PAGE_SIZE)); static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, @@ -66,7 +66,7 @@ static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj, return n; } -static BIN_ATTR_RO(cpulist, 0); +static BIN_ATTR_RO(cpulist, (((NR_CPUS * 6) > PAGE_SIZE) ? NR_CPUS *6 : PAGE_SIZE)); /** * struct node_access_nodes - Access class device to hold user visible -- 2.31.1