From patchwork Thu Sep 22 16:43:59 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vlastimil Babka X-Patchwork-Id: 673541 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3sg2Q33kRCz9t1Y for ; Fri, 23 Sep 2016 02:44:11 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934543AbcIVQoI (ORCPT ); Thu, 22 Sep 2016 12:44:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:52152 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933227AbcIVQoG (ORCPT ); Thu, 22 Sep 2016 12:44:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 3558DAB9F; Thu, 22 Sep 2016 16:44:05 +0000 (UTC) From: Vlastimil Babka To: Alexander Viro , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , netdev@vger.kernel.org, Eric Dumazet , Vlastimil Babka Subject: [PATCH v2] fs/select: add vmalloc fallback for select(2) Date: Thu, 22 Sep 2016 18:43:59 +0200 Message-Id: <20160922164359.9035-1-vbabka@suse.cz> X-Mailer: git-send-email 2.10.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The select(2) syscall performs a kmalloc(size, GFP_KERNEL) where size grows with the number of fds passed. We had a customer report page allocation failures of order-4 for this allocation. This is a costly order, so it might easily fail, as the VM expects such allocation to have a lower-order fallback. Such trivial fallback is vmalloc(), as the memory doesn't have to be physically contiguous. Also the allocation is temporary for the duration of the syscall, so it's unlikely to stress vmalloc too much. Note that the poll(2) syscall seems to use a linked list of order-0 pages, so it doesn't need this kind of fallback. [eric.dumazet@gmail.com: fix failure path logic] Signed-off-by: Vlastimil Babka --- fs/select.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/select.c b/fs/select.c index 8ed9da50896a..b99e98524fde 100644 --- a/fs/select.c +++ b/fs/select.c @@ -29,6 +29,7 @@ #include #include #include +#include #include @@ -558,6 +559,7 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, struct fdtable *fdt; /* Allocate small arguments on the stack to save memory and be faster */ long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; + unsigned long alloc_size; ret = -EINVAL; if (n < 0) @@ -580,8 +582,12 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, bits = stack_fds; if (size > sizeof(stack_fds) / 6) { /* Not enough space in on-stack array; must use kmalloc */ + alloc_size = 6 * size; ret = -ENOMEM; - bits = kmalloc(6 * size, GFP_KERNEL); + bits = kmalloc(alloc_size, GFP_KERNEL|__GFP_NOWARN); + if (!bits && alloc_size > PAGE_SIZE) + bits = vmalloc(alloc_size); + if (!bits) goto out_nofds; } @@ -618,7 +624,7 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, out: if (bits != stack_fds) - kfree(bits); + kvfree(bits); out_nofds: return ret; }