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=-6.5 required=3.0 tests=BAYES_00,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 BA6A9C4338F for ; Thu, 5 Aug 2021 10:19:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A34A561107 for ; Thu, 5 Aug 2021 10:19:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240087AbhHEKTl (ORCPT ); Thu, 5 Aug 2021 06:19:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:39385 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240017AbhHEKTi (ORCPT ); Thu, 5 Aug 2021 06:19:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628158764; 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; bh=tPLv8/FqEnF6zrBT0uL4PeS5Q8+ujikNSGDD6GSwxto=; b=L5I/eSx6icegeYWa5DasTkK8aCr1SNwvNF7vkBiYjcOb+e5rLI8PfSPU3ptY4Bg/HW+4cf H/FaG3JxwZp4ebmDvutdH2XBAEXA7Er/7Qo1CrNwR+rnHX53eAsKke1lq+Bib0BE7NvhMu 1O0nYX9DaQx97EYXUN1yJKZfwQqSNO0= 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-139-9SCv9aALMnql9atHZRlg2g-1; Thu, 05 Aug 2021 06:19:21 -0400 X-MC-Unique: 9SCv9aALMnql9atHZRlg2g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 852AC87D541; Thu, 5 Aug 2021 10:19:19 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.22.32.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id E55B0100238C; Thu, 5 Aug 2021 10:19:17 +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 To: linux-fsdevel@vger.kernel.org cc: dhowells@redhat.com, jlayton@kernel.org, Matthew Wilcox , Christoph Hellwig , Linus Torvalds , dchinner@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Could it be made possible to offer "supplementary" data to a DIO write ? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1017389.1628158757.1@warthog.procyon.org.uk> Date: Thu, 05 Aug 2021 11:19:17 +0100 Message-ID: <1017390.1628158757@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I'm working on network filesystem write helpers to go with the read helpers, and I see situations where I want to write a few bytes to the cache, but have more available that could be written also if it would allow the filesystem/blockdev to optimise its layout. Say, for example, I need to write a 3-byte change from a page, where that page is part of a 256K sequence in the pagecache. Currently, I have to round the 3-bytes out to DIO size/alignment, but I could say to the API, for example, "here's a 256K iterator - I need bytes 225-227 written, but you can write more if you want to"? Would it be useful/feasible to have some sort of interface that allows the offer to be made? David