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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 16AF1C55199 for ; Mon, 27 Apr 2020 12:28:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E05A220575 for ; Mon, 27 Apr 2020 12:28:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="h4uZN/H6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727111AbgD0M2m (ORCPT ); Mon, 27 Apr 2020 08:28:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43532 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726260AbgD0M2l (ORCPT ); Mon, 27 Apr 2020 08:28:41 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A91EAC0610D5; Mon, 27 Apr 2020 05:28:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Wzixkdd1MP05tKyiJudvvJUbNJ4oUXlhwu6lo0T90lk=; b=h4uZN/H6Mu3d0zPdDsclCVH32p 44gY3nD6XgbLkqBBMl44AzSP/BJE3KBzRAPQwmBogEvavTEhIQUL3ocaF+cw7UkzuVAwITD4seBgk Pp8Hl1+tIQ8RODfstqU0/krSNx7E830cBVrxSyf5dfg0gpQoKrJKe2M5AynwMKOl0n3mi6Pl4oFKf efaEddM5vpsfG757hkc2v8IEonhVlf8jAZ4wp/U05w15FPDDSa7fkY0VDdkD1WHqV691GKsmZEkS8 SOQI03I+FKN/fUWcflc8dcvjdXytbEbhLDXDLTXiJZruWD/RddNBs2RHT5uDy951iViKV1ctgL7yg iJXmOD4A==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jT2sG-0003WE-Dr; Mon, 27 Apr 2020 12:28:36 +0000 Date: Mon, 27 Apr 2020 05:28:36 -0700 From: Matthew Wilcox To: Shiyang Ruan Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-nvdimm@lists.01.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, darrick.wong@oracle.com, dan.j.williams@intel.com, david@fromorbit.com, hch@lst.de, rgoldwyn@suse.de, qi.fuli@fujitsu.com, y-goto@fujitsu.com Subject: Re: [RFC PATCH 0/8] dax: Add a dax-rmap tree to support reflink Message-ID: <20200427122836.GD29705@bombadil.infradead.org> References: <20200427084750.136031-1-ruansy.fnst@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200427084750.136031-1-ruansy.fnst@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 27, 2020 at 04:47:42PM +0800, Shiyang Ruan wrote: > This patchset is a try to resolve the shared 'page cache' problem for > fsdax. > > In order to track multiple mappings and indexes on one page, I > introduced a dax-rmap rb-tree to manage the relationship. A dax entry > will be associated more than once if is shared. At the second time we > associate this entry, we create this rb-tree and store its root in > page->private(not used in fsdax). Insert (->mapping, ->index) when > dax_associate_entry() and delete it when dax_disassociate_entry(). Do we really want to track all of this on a per-page basis? I would have thought a per-extent basis was more useful. Essentially, create a new address_space for each shared extent. Per page just seems like a huge overhead.