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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2A9FEB64DC for ; Thu, 20 Jul 2023 14:52:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231797AbjGTOwY (ORCPT ); Thu, 20 Jul 2023 10:52:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230034AbjGTOwW (ORCPT ); Thu, 20 Jul 2023 10:52:22 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0F1C26B0 for ; Thu, 20 Jul 2023 07:51:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689864694; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AkiNNvhZXBOhwappo5DsNfWFblN13jxPHvb5/iriC0Y=; b=VocUckPowaQyB9yrnL79v6fwLPnFNx4VQiVbf1dzJRob3jMWqtemnaB7O5Oe+pcpHidqoq Ees2sRGi/r8AVZhPD/kJmMYOorJCli1BhQZKSr1DRU2JMInwQOBelIYpwk3Vab2a5O2fpd Tu4LKrs1KvAoGdOEQWA3+PopAMMX6SQ= Received: from mail-qv1-f69.google.com (mail-qv1-f69.google.com [209.85.219.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-533-s7npWQIwOuqQJw71wMB6Fg-1; Thu, 20 Jul 2023 10:51:33 -0400 X-MC-Unique: s7npWQIwOuqQJw71wMB6Fg-1 Received: by mail-qv1-f69.google.com with SMTP id 6a1803df08f44-635a4267cf5so11067046d6.2 for ; Thu, 20 Jul 2023 07:51:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689864692; x=1690469492; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=AkiNNvhZXBOhwappo5DsNfWFblN13jxPHvb5/iriC0Y=; b=eq5aM0TBESQ5KR38tc4eIQB5yh32gyc3eI/a/OT2jvmWytZX6nHs9xGkksJNaU60QM 6fSaikx1HzwUvAYYt6NIeXYx0Gkd5fo6NFWnE6BDpyuRCwk7wzmpPbvbzIHkc3jhMVvV i5wtUkmoa5cY55E+b3FEGYZXD0exbbhxAecpuhI0aRcooGi22tHAqksddQXVI3uVkMJy vVDB0cYmaV7UnPPCnd43O17LvqmqIeNZKnFOCXPdfcE26qEYZlisG1knfm95pTXHpxwN zdP5bIbksnYZtyEbzGje7jRyWyISkcaLp7STiYakeCK7gUEuoeSj51+uc+TZXRGiuuxI f7fA== X-Gm-Message-State: ABy/qLZHIOxMjegvmX4MRbL7AxoIeBiFH3Rxw5kg1z0qQfr63SV1SCcF Tv72OhYHj8UvIJ8GXmYzTtatrrnp+/DAeY+UhSQyaeJhcKx7j9Q1ws7cVEvvGAJ6GK9pSPX9UDx 7wV+ebVw+JEcwIJZWxSI10KgRvw== X-Received: by 2002:a0c:e012:0:b0:63c:c041:ef7c with SMTP id j18-20020a0ce012000000b0063cc041ef7cmr4998995qvk.16.1689864692600; Thu, 20 Jul 2023 07:51:32 -0700 (PDT) X-Google-Smtp-Source: APBJJlGG9WiVjMAJC0jyp6FJ1iLPNYyic/lNvrnvPP6HMAfS4d7vXSpGs/eQms+dzXXL9v8chg2XyA== X-Received: by 2002:a0c:e012:0:b0:63c:c041:ef7c with SMTP id j18-20020a0ce012000000b0063cc041ef7cmr4998979qvk.16.1689864692339; Thu, 20 Jul 2023 07:51:32 -0700 (PDT) Received: from [172.16.0.7] ([209.73.90.46]) by smtp.gmail.com with ESMTPSA id u4-20020a0cf1c4000000b006375f9fd170sm429007qvl.34.2023.07.20.07.51.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jul 2023 07:51:31 -0700 (PDT) Message-ID: <251d9862-e335-243e-d65a-c5538b4df253@redhat.com> Date: Thu, 20 Jul 2023 09:51:30 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: allow building a kernel without buffer_heads To: Christoph Hellwig , Jens Axboe Cc: "Darrick J. Wong" , Andrew Morton , Matthew Wilcox , Christian Brauner , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cluster-devel References: <20230720140452.63817-1-hch@lst.de> Content-Language: en-US From: Bob Peterson In-Reply-To: <20230720140452.63817-1-hch@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 7/20/23 9:04 AM, Christoph Hellwig wrote: > Hi all, > > This series allows to build a kernel without buffer_heads, which I > think is useful to show where the dependencies are, and maybe also > for some very much limited environments, where people just needs > xfs and/or btrfs and some of the read-only block based file systems. > > It first switches buffered writes (but not writeback) for block devices > to use iomap unconditionally, but still using buffer_heads, and then > adds a CONFIG_BUFFER_HEAD selected by all file systems that need it > (which is most block based file systems), makes the buffer_head support > in iomap optional, and adds an alternative implementation of the block > device address_operations using iomap. This latter implementation > will also be useful to support block size > PAGE_SIZE for block device > nodes as buffer_heads won't work very well for that. > > Note that for now the md software raid drivers is also disabled as it has > some (rather questionable) buffer_head usage in the unconditionally built > bitmap code. I have a series pending to make the bitmap code conditional > and deprecated it, but it hasn't been merged yet. > > Changes since v1: > - drop the already merged prep patches > - depend on FS_IOMAP not IOMAP > - pick a better new name for block_page_mkwrite_return > Hi Christoph, Gfs2 still uses buffer_heads to manage the metadata being pushed through its journals. We've been reducing our dependency on them but eliminating them altogether is a large and daunting task. We can still work toward that goal, but it will take time. Bob Peterson