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 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 BE5FAC33CB2 for ; Wed, 15 Jan 2020 14:15:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B7532467A for ; Wed, 15 Jan 2020 14:15:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SBa2IZ4O" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730728AbgAOOPp (ORCPT ); Wed, 15 Jan 2020 09:15:45 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:29707 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730589AbgAOOPo (ORCPT ); Wed, 15 Jan 2020 09:15:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579097743; 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=OUWgGIVsJ8NZwOLyNUY7Hd2Km2oSlO39xhYqMQdHPRE=; b=SBa2IZ4OujszdbTdvi6vrsZ8WupQHWa0QTj3+i1P7L91iJV9jGhD4dl+qCXsgW7+izJ+VA 8NcDvQevfqKQUlTeo8xvcEXbLsnsj8dDG8BxB2+nihCY5gzsQAfYDeRO6X852DVrkwHyAn etKCTbACmZ205VmLFGDW+ysamgk6Kok= 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-301-amsWRQ3cP4KKzpO788M-xQ-1; Wed, 15 Jan 2020 09:15:39 -0500 X-MC-Unique: amsWRQ3cP4KKzpO788M-xQ-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 A81BA801A05; Wed, 15 Jan 2020 14:15:37 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-52.rdu2.redhat.com [10.10.120.52]) by smtp.corp.redhat.com (Postfix) with ESMTP id 420885C545; Wed, 15 Jan 2020 14:15:35 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20200115083854.GB23039@lst.de> References: <20200115083854.GB23039@lst.de> <4467.1579020509@warthog.procyon.org.uk> To: Christoph Hellwig Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, tytso@mit.edu, adilger.kernel@dilger.ca, darrick.wong@oracle.com, clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Problems with determining data presence by examining extents? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <24479.1579097734.1@warthog.procyon.org.uk> Date: Wed, 15 Jan 2020 14:15:34 +0000 Message-ID: <24480.1579097734@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org Christoph Hellwig wrote: > The whole idea of an out of band interface is going to be racy and suffer > from implementation loss. I think what you want is something similar to > the NFSv4.2 READ_PLUS operation - give me that if there is any and > otherwise tell me that there is a hole. I think this could be a new > RWF_NOHOLE or similar flag, just how to return the hole size would be > a little awkward. Maybe return a specific negative error code (ENODATA?) > and advance the iov anyway. Just having call_iter_read() return a short read could be made to suffice... provided the filesystem doesn't return data I haven't written in (which could cause apparent corruption) and does return data I have written in (otherwise I have to go back to the server). David