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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 37CC0C47426 for ; Tue, 22 Sep 2020 11:48:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 99896239D2 for ; Tue, 22 Sep 2020 11:48:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hQHYz1cu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 99896239D2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E3A3A90006A; Tue, 22 Sep 2020 07:48:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DE981900063; Tue, 22 Sep 2020 07:48:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CD7B290006A; Tue, 22 Sep 2020 07:48:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0229.hostedemail.com [216.40.44.229]) by kanga.kvack.org (Postfix) with ESMTP id B08B6900063 for ; Tue, 22 Sep 2020 07:48:54 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 702FB1EE6 for ; Tue, 22 Sep 2020 11:48:54 +0000 (UTC) X-FDA: 77290525788.07.power31_531509b2714d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 55FA41803F9A3 for ; Tue, 22 Sep 2020 11:48:54 +0000 (UTC) X-HE-Tag: power31_531509b2714d X-Filterd-Recvd-Size: 3717 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf25.hostedemail.com (Postfix) with ESMTP for ; Tue, 22 Sep 2020 11:48:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600775333; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xQ6xAU5ZnYayBNRYBEJtPnFAgdA/Gx4Gks29IeOF6vc=; b=hQHYz1cuNxGSo0pv0u1abUwaW69z1LUbfOSudju20/Q3d5I87ZQEB56ZUZEeVUlO0iWsib JFyJ+WcQ/1tI8ATnUxrBFdEwVeYYthWu532Oguk7qYJcSUHqfyCaZswsmhuPMyyCfnuqVu Nhhj0gfgWsvMKEwUkJgR3oV6ZiiXHp0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-559-IQMQgRZPNNOtLsI3btQlVg-1; Tue, 22 Sep 2020 07:48:51 -0400 X-MC-Unique: IQMQgRZPNNOtLsI3btQlVg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 317ED57001; Tue, 22 Sep 2020 11:48:48 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.146]) by smtp.corp.redhat.com (Postfix) with SMTP id 4FBB57366B; Tue, 22 Sep 2020 11:48:41 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 22 Sep 2020 13:48:47 +0200 (CEST) Date: Tue, 22 Sep 2020 13:48:40 +0200 From: Oleg Nesterov To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Linus Torvalds , Michal Hocko , Kirill Shutemov , Jann Horn , Kirill Tkhai , Hugh Dickins , Leon Romanovsky , Jan Kara , John Hubbard , Christoph Hellwig , Andrew Morton , Jason Gunthorpe , Andrea Arcangeli Subject: Re: [PATCH 4/5] mm: Do early cow for pinned pages during fork() for ptes Message-ID: <20200922114839.GC11679@redhat.com> References: <20200921211744.24758-1-peterx@redhat.com> <20200921212028.25184-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200921212028.25184-1-peterx@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 09/21, Peter Xu wrote: > > @@ -859,6 +989,25 @@ static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm, > spin_needbreak(src_ptl) || spin_needbreak(dst_ptl)) > break; > } > + > + if (unlikely(data.cow_new_page)) { > + /* > + * If cow_new_page set, we must be at the 2nd round of > + * a previous COPY_MM_BREAK_COW. Try to arm the new > + * page now. Note that in all cases page_break_cow() > + * will properly release the objects in copy_mm_data. > + */ > + WARN_ON_ONCE(copy_ret != COPY_MM_BREAK_COW); > + if (pte_install_copied_page(dst_mm, new, src_pte, > + dst_pte, addr, rss, > + &data)) { > + /* We installed the pte successfully; move on */ > + progress++; > + continue; I'm afraid I misread this patch too ;) But it seems to me in this case the main loop can really "leak" COPY_MM_BREAK_COW. Suppose the the next 31 pte's are pte_none() and need_resched() is true. No? Oleg.