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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D86AEC43217 for ; Thu, 4 Nov 2021 18:10:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1DD1611EF for ; Thu, 4 Nov 2021 18:10:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234098AbhKDSNK (ORCPT ); Thu, 4 Nov 2021 14:13:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234094AbhKDSNJ (ORCPT ); Thu, 4 Nov 2021 14:13:09 -0400 Received: from mail-pl1-x631.google.com (mail-pl1-x631.google.com [IPv6:2607:f8b0:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF31AC061208 for ; Thu, 4 Nov 2021 11:10:30 -0700 (PDT) Received: by mail-pl1-x631.google.com with SMTP id r5so8637306pls.1 for ; Thu, 04 Nov 2021 11:10:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=7mdrEIaynFJhMAYVbY2RCFSQ3xBs/5manpadoyeA8Jg=; b=0YEcomScst+1AzYcEtB+P3/DmeUM77501UDi4utLMr5xdKJlnd8UevBd12j9FnZ3vM pfReEE9Mys+ZVEwliSTF7urxA8Wo0+Hi1QGvdNyLT71G18SgBjzWHXiXc01F/GMcT30o 4sj59niVU83geSVU+jTxOcRmF241hREk19CsoBH8kxr2RQdc6rHN1RFVCxVTxuFK53C5 ubx4NqJpME+C1zDILd+MfHjSjbqUFn2nDpjUaVUu+wM8te1yVWJyRStj28nUJ7WDbMUk H2RDjE1nkFNI+5JNwfhWiSHo+ZLBnVukougjDJ/S9PImKe7sfLSLlzrr4uAIBYjBE48z eouQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=7mdrEIaynFJhMAYVbY2RCFSQ3xBs/5manpadoyeA8Jg=; b=uhuEEWLAo+6FVQl2+6fQj+W9sLaHc2Zzbp3l2wxmR0uzVpQ2Ha0TgQ66UFQ5dac/ah 6+n5FM+85tCVELytro9vha/0zoQJdyHHDAagEvrFRueDQqt/xREpa75q+n2Q15ugd7PQ jcMV12BeZitz23SbQ2dkslQ54Ss0YgMbvb283A+fcq5WckKucR5W9pZEVeVK+KMcSZvG SBDMOQGv8jBTaSHIoBnjdAX7tT4z7iPa8dWk9QIW4GoAOh4oBMQfLOhjbFsSgEUNC9FL enZ0DbAbd5O9ipfqpvpxH42b2RtMfJD3VgS7AoVdXIKzYQ/i0q8czdpwNMTlkadPkTdO t93A== X-Gm-Message-State: AOAM533Yzg2Z0Vm1x1R7ngpNgVBKxLFNCJbsj54n7cl4uYjKSfV7ZNYM l/bFQK4ifkKpCouJIkUFsOZVPUHgkfpTUOQEvIDrMg== X-Google-Smtp-Source: ABdhPJxpE7179nYWnBAffbsem/btoh3olrocKEPy5McMuIBWtGLmZ02iwXqFLVvSNceMnE3VXVk1wLsDAvNCq2GAmrQ= X-Received: by 2002:a17:902:b697:b0:141:c7aa:e10f with SMTP id c23-20020a170902b69700b00141c7aae10fmr33445935pls.18.1636049430346; Thu, 04 Nov 2021 11:10:30 -0700 (PDT) MIME-Version: 1.0 References: <20211018044054.1779424-1-hch@lst.de> <21ff4333-e567-2819-3ae0-6a2e83ec7ce6@sandeen.net> <20211104081740.GA23111@lst.de> <20211104173417.GJ2237511@magnolia> <20211104173559.GB31740@lst.de> In-Reply-To: <20211104173559.GB31740@lst.de> From: Dan Williams Date: Thu, 4 Nov 2021 11:10:19 -0700 Message-ID: Subject: Re: futher decouple DAX from block devices To: Christoph Hellwig Cc: "Darrick J. Wong" , Eric Sandeen , Mike Snitzer , Ira Weiny , device-mapper development , linux-xfs , Linux NVDIMM , linux-s390 , linux-fsdevel , linux-erofs@lists.ozlabs.org, linux-ext4 , virtualization@lists.linux-foundation.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Nov 4, 2021 at 10:36 AM Christoph Hellwig wrote: > > On Thu, Nov 04, 2021 at 10:34:17AM -0700, Darrick J. Wong wrote: > > /me wonders, are block devices going away? Will mkfs.xfs have to learn > > how to talk to certain chardevs? I guess jffs2 and others already do > > that kind of thing... but I suppose I can wait for the real draft to > > show up to ramble further. ;) > > Right now I've mostly been looking into the kernel side. An no, I > do not expect /dev/pmem* to go away as you'll still need it for a > not DAX aware file system and/or application (such as mkfs initially). > > But yes, just pointing mkfs to the chardev should be doable with very > little work. We can point it to a regular file after all. Note that I've avoided implementing read/write fops for dax devices partly out of concern for not wanting to figure out shared-mmap vs write coherence issues, but also because of a bet with Dave Hansen that device-dax not grow features like what happened to hugetlbfs. So it would seem mkfs would need to switch to mmap I/O, or bite the bullet and implement read/write fops in the driver.