From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754704AbaE1JAH (ORCPT ); Wed, 28 May 2014 05:00:07 -0400 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:44415 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754261AbaE1JAA (ORCPT ); Wed, 28 May 2014 05:00:00 -0400 Date: Wed, 28 May 2014 10:59:54 +0200 From: Heiko Carstens To: Christoph Hellwig , Andrew Morton , KAMEZAWA Hiroyuki , Andrea Righi , Eric Dumazet , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Hendrik Brueckner , Thorsten Diehl , Ian Kent , "Elliott, Robert (Server Storage)" Subject: [PATCH 1/2] fs: proc/stat: use num_online_cpus() for buffer size Message-ID: <20140528085954.GB4219@osiris> References: <20140521122521.GB7471@osiris> <20140521143229.GA32011@infradead.org> <20140528085841.GA4219@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140528085841.GA4219@osiris> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14052808-0342-0000-0000-000008F0259B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The number of bytes contained 'within' /proc/stat depends on the number of online cpus and not of the numbe of possible cpus. This reduces the number of bytes requested for the initial buffer allocation within stat_open(). Which is usually way too high and for nr_possible_cpus() == 256 cpus would result in an order 4 allocation. Order 4 allocations however may fail if memory is fragmented and we would end up with an unreadable /proc/stat file: 62129.701569] sadc: page allocation failure: order:4, mode:0x1040d0 [62129.701573] CPU: 1 PID: 192063 Comm: sadc Not tainted 3.10.0-123.el7.s390x #1 [...] [62129.701586] Call Trace: [62129.701588] ([<0000000000111fbe>] show_trace+0xe6/0x130) [62129.701591] [<0000000000112074>] show_stack+0x6c/0xe8 [62129.701593] [<000000000020d356>] warn_alloc_failed+0xd6/0x138 [62129.701596] [<00000000002114d2>] __alloc_pages_nodemask+0x9da/0xb68 [62129.701598] [<000000000021168e>] __get_free_pages+0x2e/0x58 [62129.701599] [<000000000025a05c>] kmalloc_order_trace+0x44/0xc0 [62129.701602] [<00000000002f3ffa>] stat_open+0x5a/0xd8 [62129.701604] [<00000000002e9aaa>] proc_reg_open+0x8a/0x140 [62129.701606] [<0000000000273b64>] do_dentry_open+0x1bc/0x2c8 [62129.701608] [<000000000027411e>] finish_open+0x46/0x60 [62129.701610] [<000000000028675a>] do_last+0x382/0x10d0 [62129.701612] [<0000000000287570>] path_openat+0xc8/0x4f8 [62129.701614] [<0000000000288bde>] do_filp_open+0x46/0xa8 [62129.701616] [<000000000027541c>] do_sys_open+0x114/0x1f0 [62129.701618] [<00000000005b1c1c>] sysc_tracego+0x14/0x1a Signed-off-by: Heiko Carstens --- fs/proc/stat.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/proc/stat.c b/fs/proc/stat.c index 9d231e9e5f0e..3898ca5f1e92 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -184,7 +184,7 @@ static int show_stat(struct seq_file *p, void *v) static int stat_open(struct inode *inode, struct file *file) { - size_t size = 1024 + 128 * num_possible_cpus(); + size_t size = 1024 + 128 * num_online_cpus(); char *buf; struct seq_file *m; int res; -- 1.8.5.5