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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 1A746C35E04 for ; Tue, 25 Feb 2020 19:37:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E73402084E for ; Tue, 25 Feb 2020 19:37:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MmFIV2bC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730671AbgBYTh1 (ORCPT ); Tue, 25 Feb 2020 14:37:27 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:45138 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728555AbgBYThW (ORCPT ); Tue, 25 Feb 2020 14:37:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582659441; 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=3454YjUXRoDS+24Lzxnu4Pv0NqG7YV73o/VGu7/5u2E=; b=MmFIV2bCFfKsScL4zbRKXb9IbJaKNNlhasHYPnSW6EodaAzOvlGhIFBPFqnHN2hU2xfdmc 6IZuIE8eXvoviUr+/7eQLNDd9ekMwTwuGpgD/oH4iQg2jCOn2fAejJX50YRRR0sEn1RQZh WXBCorgyRMvo86IbzlBo0yzLQoCcLLI= 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-367-9ulGlCEBOoewJwoiFtQzDg-1; Tue, 25 Feb 2020 14:37:17 -0500 X-MC-Unique: 9ulGlCEBOoewJwoiFtQzDg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2852C8017CC; Tue, 25 Feb 2020 19:37:15 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C0FC65C296; Tue, 25 Feb 2020 19:37:13 +0000 (UTC) From: Jeff Moyer To: Christoph Hellwig , jhallida@redhat.com Cc: Dave Chinner , ira.weiny@intel.com, linux-kernel@vger.kernel.org, Alexander Viro , "Darrick J. Wong" , Dan Williams , "Theodore Y. Ts'o" , Jan Kara , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH V4 07/13] fs: Add locking for a dynamic address space operations state References: <20200221004134.30599-1-ira.weiny@intel.com> <20200221004134.30599-8-ira.weiny@intel.com> <20200221174449.GB11378@lst.de> <20200221224419.GW10776@dread.disaster.area> <20200224175603.GE7771@lst.de> <20200225000937.GA10776@dread.disaster.area> <20200225173633.GA30843@lst.de> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Tue, 25 Feb 2020 14:37:12 -0500 In-Reply-To: <20200225173633.GA30843@lst.de> (Christoph Hellwig's message of "Tue, 25 Feb 2020 18:36:33 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Christoph Hellwig writes: > And my point is that if we ensure S_DAX can only be checked if there > are no blocks on the file, is is fairly easy to provide the same > guarantee. And I've not heard any argument that we really need more > flexibility than that. In fact I think just being able to change it > on the parent directory and inheriting the flag might be more than > plenty, which would lead to a very simple implementation without any > of the crazy overhead in this series. I know of one user who had at least mentioned it to me, so I cc'd him. Jonathan, can you describe your use case for being able to change a file between dax and non-dax modes? Or, if I'm misremembering, just correct me? Thanks! Jeff