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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 0B4DAC41517 for ; Fri, 26 Jul 2019 08:44:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E17F322BEF for ; Fri, 26 Jul 2019 08:44:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726431AbfGZIo1 convert rfc822-to-8bit (ORCPT ); Fri, 26 Jul 2019 04:44:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725815AbfGZIo1 (ORCPT ); Fri, 26 Jul 2019 04:44:27 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9136830A6960; Fri, 26 Jul 2019 08:44:26 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 856EC101E241; Fri, 26 Jul 2019 08:44:24 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 26 Jul 2019 10:44:26 +0200 (CEST) Date: Fri, 26 Jul 2019 10:44:23 +0200 From: Oleg Nesterov To: Song Liu Cc: lkml , Linux-MM , Andrew Morton , "matthew.wilcox@oracle.com" , "kirill.shutemov@linux.intel.com" , "peterz@infradead.org" , "rostedt@goodmis.org" , Kernel Team , "william.kucharski@oracle.com" Subject: Re: [PATCH v8 2/4] uprobe: use original page when all uprobes are removed Message-ID: <20190726084423.GA16112@redhat.com> References: <20190724083600.832091-1-songliubraving@fb.com> <20190724083600.832091-3-songliubraving@fb.com> <20190724113711.GE21599@redhat.com> <20190725081414.GB4707@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Fri, 26 Jul 2019 08:44:26 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/25, Song Liu wrote: > > I guess I know the case now. We can probably avoid this with an simple > check for old_page == new_page? better yet, I think we can check PageAnon(old_page) and avoid the unnecessary __replace_page() in this case. See the patch below. Anyway, why __replace_page() needs to lock both pages? This doesn't look nice even if it were correct. I think it can do lock_page(old_page) later. Oleg. --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -488,6 +488,10 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, ref_ctr_updated = 1; } + ret = 0; + if (!is_register && !PageAnon(old_page)) + goto put_old; + ret = anon_vma_prepare(vma); if (ret) goto put_old;