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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA6C2C3279B for ; Mon, 2 Jul 2018 13:40:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 981312525F for ; Mon, 2 Jul 2018 13:40:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 981312525F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575AbeGBNks (ORCPT ); Mon, 2 Jul 2018 09:40:48 -0400 Received: from mx2.suse.de ([195.135.220.15]:46108 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752401AbeGBNkp (ORCPT ); Mon, 2 Jul 2018 09:40:45 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E6E1CAD12; Mon, 2 Jul 2018 13:40:43 +0000 (UTC) Date: Mon, 2 Jul 2018 15:40:43 +0200 From: Michal Hocko To: Yang Shi Cc: willy@infradead.org, ldufour@linux.vnet.ibm.com, akpm@linux-foundation.org, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, tglx@linutronix.de, hpa@zytor.com, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v3 PATCH 2/5] mm: introduce VM_DEAD flag Message-ID: <20180702134043.GW19043@dhcp22.suse.cz> References: <1530311985-31251-1-git-send-email-yang.shi@linux.alibaba.com> <1530311985-31251-3-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1530311985-31251-3-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 30-06-18 06:39:42, Yang Shi wrote: > VM_DEAD flag is used to mark a vma is being unmapped, access to this > area will trigger SIGSEGV. > > This flag will be used by the optimization for unmapping large address > space (>= 1GB) in the later patch. It is 64 bit only at the moment, > since: > * we used up vm_flags bit for 32 bit > * 32 bit machine typically will not have such large mapping > > All architectures, which support 64 bit, need check this flag in their > page fault handler. This is implemented in later patches. Please add a new flag with its users. There is simply no way to tell the semantic from the above description and the patch as well. > Suggested-by: Michal Hocko > Signed-off-by: Yang Shi > --- > include/linux/mm.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index a0fbb9f..28a3906 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -242,6 +242,12 @@ extern int overcommit_kbytes_handler(struct ctl_table *, int, void __user *, > #endif > #endif /* CONFIG_ARCH_HAS_PKEYS */ > > +#ifdef CONFIG_64BIT > +#define VM_DEAD BIT(37) /* bit only usable on 64 bit kernel */ > +#else > +#define VM_DEAD 0 > +#endif > + > #if defined(CONFIG_X86) > # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ > #elif defined(CONFIG_PPC) > -- > 1.8.3.1 -- Michal Hocko SUSE Labs