From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754888AbaFPJGC (ORCPT ); Mon, 16 Jun 2014 05:06:02 -0400 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:43785 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754726AbaFPJFE (ORCPT ); Mon, 16 Jun 2014 05:05:04 -0400 From: Heiko Carstens To: Andrew Morton Cc: David Rientjes , Ian Kent , Hendrik Brueckner , Thorsten Diehl , Andrea Righi , Christoph Hellwig , Al Viro , Stefan Bader , linux-kernel@vger.kernel.org, Heiko Carstens Subject: [PATCH 2/2] fs/seq_file: fallback to vmalloc allocation Date: Mon, 16 Jun 2014 11:04:52 +0200 Message-Id: <1402909492-36486-3-git-send-email-heiko.carstens@de.ibm.com> X-Mailer: git-send-email 1.8.5.5 In-Reply-To: <1402909492-36486-1-git-send-email-heiko.carstens@de.ibm.com> References: <1402909492-36486-1-git-send-email-heiko.carstens@de.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14061609-0342-0000-0000-0000001CD566 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are a couple of seq_files which use the single_open() interface. This interface requires that the whole output must fit into a single buffer. E.g. for /proc/stat allocation failures have been observed because an order-4 memory allocation failed due to memory fragmentation. In such situations reading /proc/stat is not possible anymore. Therefore change the seq_file code to fallback to vmalloc allocations which will usually result in a couple of order-0 allocations and hence also work if memory is fragmented. For reference a call trace where reading from /proc/stat failed: [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/seq_file.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) diff --git a/fs/seq_file.c b/fs/seq_file.c index 1d641bb108d2..3857b720cb1b 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -8,8 +8,10 @@ #include #include #include +#include #include #include +#include #include #include @@ -30,6 +32,16 @@ static void seq_set_overflow(struct seq_file *m) m->count = m->size; } +static void *seq_buf_alloc(unsigned long size) +{ + void *buf; + + buf = kmalloc(size, GFP_KERNEL | __GFP_NOWARN); + if (!buf && size > PAGE_SIZE) + buf = vmalloc(size); + return buf; +} + /** * seq_open - initialize sequential file * @file: file we initialize @@ -96,7 +108,7 @@ static int traverse(struct seq_file *m, loff_t offset) return 0; } if (!m->buf) { - m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); + m->buf = seq_buf_alloc(m->size = PAGE_SIZE); if (!m->buf) return -ENOMEM; } @@ -135,9 +147,9 @@ static int traverse(struct seq_file *m, loff_t offset) Eoverflow: m->op->stop(m, p); - kfree(m->buf); + kvfree(m->buf); m->count = 0; - m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); + m->buf = seq_buf_alloc(m->size <<= 1); return !m->buf ? -ENOMEM : -EAGAIN; } @@ -192,7 +204,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) /* grab buffer if we didn't have one */ if (!m->buf) { - m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL); + m->buf = seq_buf_alloc(m->size = PAGE_SIZE); if (!m->buf) goto Enomem; } @@ -232,9 +244,9 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) if (m->count < m->size) goto Fill; m->op->stop(m, p); - kfree(m->buf); + kvfree(m->buf); m->count = 0; - m->buf = kmalloc(m->size <<= 1, GFP_KERNEL); + m->buf = seq_buf_alloc(m->size <<= 1); if (!m->buf) goto Enomem; m->version = 0; @@ -350,7 +362,7 @@ EXPORT_SYMBOL(seq_lseek); int seq_release(struct inode *inode, struct file *file) { struct seq_file *m = file->private_data; - kfree(m->buf); + kvfree(m->buf); kfree(m); return 0; } @@ -605,13 +617,13 @@ EXPORT_SYMBOL(single_open); int single_open_size(struct file *file, int (*show)(struct seq_file *, void *), void *data, size_t size) { - char *buf = kmalloc(size, GFP_KERNEL); + char *buf = seq_buf_alloc(size); int ret; if (!buf) return -ENOMEM; ret = single_open(file, show, data); if (ret) { - kfree(buf); + kvfree(buf); return ret; } ((struct seq_file *)file->private_data)->buf = buf; -- 1.8.5.5