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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 EB92FC433FE for ; Wed, 22 Sep 2021 02:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA4826120C for ; Wed, 22 Sep 2021 02:38:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229945AbhIVCjb (ORCPT ); Tue, 21 Sep 2021 22:39:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:55838 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229644AbhIVCjb (ORCPT ); Tue, 21 Sep 2021 22:39:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 070E261184; Wed, 22 Sep 2021 02:38:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632278282; bh=o0xTvVAAlxGYjHg2mWOMUzL4Sh++CYYDs0N2OMgy4tY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=opSjAt7DT3ngxcwKBLYz9jVBe/5KNdVAMgd4otBh142Fjx5K8LjUDfRFt6r39n6PT nT4UnE5MF4ydmKIWOVTIyJbXX3bebYWVj6jz34iY1/qCa6ufuPf7Tm2VIpcYSPQwot HRZWxgbKWDPR5Lisp155N0pqGU/kJ5CWUZijDF39Kw1fGsbAclpoddBCQXnfcTetgc Y0QP6Kg8Ld3YqFSxlxyzyl4I9MDEuhmaHnZpImSqjzb4eSpxNTE0EKmSt4PAE/f6Fe 1+r8fqu8wEiyOlSXRy6IZJZQvTgB2IyeDZIC9qaQtMcGvOP+zUk4YKLg1waQsS3AC7 KAR3gLOzGVS5A== Date: Tue, 21 Sep 2021 19:38:01 -0700 From: "Darrick J. Wong" To: Dan Williams Cc: Christoph Hellwig , Dave Chinner , Jane Chu , linux-xfs , linux-fsdevel Subject: Re: [PATCH 3/5] vfs: add a zero-initialization mode to fallocate Message-ID: <20210922023801.GD570615@magnolia> References: <163192864476.417973.143014658064006895.stgit@magnolia> <163192866125.417973.7293598039998376121.stgit@magnolia> <20210921004431.GO1756565@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Sep 21, 2021 at 07:16:26PM -0700, Dan Williams wrote: > On Tue, Sep 21, 2021 at 1:32 AM Christoph Hellwig wrote: > > > > On Tue, Sep 21, 2021 at 10:44:31AM +1000, Dave Chinner wrote: > > > I think this wants to be a behavioural modifier for existing > > > operations rather than an operation unto itself. i.e. similar to how > > > KEEP_SIZE modifies ALLOC behaviour but doesn't fundamentally alter > > > the guarantees ALLOC provides userspace. > > > > > > In this case, the change of behaviour over ZERO_RANGE is that we > > > want physical zeros to be written instead of the filesystem > > > optimising away the physical zeros by manipulating the layout > > > of the file. > > > > Yes. > > > > > Then we have and API that looks like: > > > > > > ALLOC - allocate space efficiently > > > ALLOC | INIT - allocate space by writing zeros to it > > > ZERO - zero data and preallocate space efficiently > > > ZERO | INIT - zero range by writing zeros to it > > > > > > Which seems to cater for all the cases I know of where physically > > > writing zeros instead of allocating unwritten extents is the > > > preferred behaviour of fallocate().... > > > > Agreed. I'm not sure INIT is really the right name, but I can't come > > up with a better idea offhand. > > FUA? As in, this is a forced-unit-access zeroing all the way to media > bypassing any mechanisms to emulate zero-filled payloads on future > reads. FALLOC_FL_ZERO_EXISTING, because you want to zero the storage that already exists at that file range? --D