From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f51.google.com (mail-ee0-f51.google.com [74.125.83.51]) by kanga.kvack.org (Postfix) with ESMTP id 0FA496B0031 for ; Sat, 19 Apr 2014 04:37:54 -0400 (EDT) Received: by mail-ee0-f51.google.com with SMTP id c13so2194792eek.24 for ; Sat, 19 Apr 2014 01:37:54 -0700 (PDT) Received: from mail-ee0-f53.google.com (mail-ee0-f53.google.com [74.125.83.53]) by mx.google.com with ESMTPS id 45si43859058eeh.153.2014.04.19.01.37.53 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 19 Apr 2014 01:37:53 -0700 (PDT) Received: by mail-ee0-f53.google.com with SMTP id b57so2182322eek.26 for ; Sat, 19 Apr 2014 01:37:53 -0700 (PDT) Message-ID: <535235DE.5080304@colorfullife.com> Date: Sat, 19 Apr 2014 10:37:50 +0200 From: Manfred Spraul MIME-Version: 1.0 Subject: Re: [PATCH] ipc/shm: Increase the defaults for SHMALL, SHMMAX to infinity References: <1397812720-5629-1-git-send-email-manfred@colorfullife.com> <1397890512.19331.21.camel@buesod1.americas.hpqcorp.net> In-Reply-To: <1397890512.19331.21.camel@buesod1.americas.hpqcorp.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Davidlohr Bueso Cc: Andrew Morton , Davidlohr Bueso , LKML , KAMEZAWA Hiroyuki , KOSAKI Motohiro , gthelen@google.com, aswin@hp.com, linux-mm@kvack.org, mtk.manpages@gmail.com On 04/19/2014 08:55 AM, Davidlohr Bueso wrote: > On Fri, 2014-04-18 at 11:18 +0200, Manfred Spraul wrote: >> - ULONG_MAX is not really infinity, but 18 Exabyte segment size and >> 75 Zettabyte total size. This should be enough for the next few weeks. >> (assuming a 64-bit system with 4k pages) Note: I found three integer overflows, none of them critical. I will send patches, I just must get a 32-bit test setup first. >> Risks: >> - The patch breaks installations that use "take current value and increase >> it a bit". [seems to exist, http://marc.info/?l=linux-mm&m=139638334330127] > This really scares me. The probability of occurrence is now much higher, > and not just theoretical. It would legitimately break userspace. That's why I mentioned it. For shmmax, there is a simple answer: Use TASK_SIZE instead of ULONG_MAX. - sufficiently far away from overflow. - values beyond TASK_SIZE are useless anyway, you can't map such segments. I don't have a good answer for shmall. 1L<<(BITS_PER_LONG-1) is too ugly. Any proposals? -- Manfred -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org