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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C0EBCE77188 for ; Wed, 8 Jan 2025 06:26:56 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4YSdHM1n8Dz3029; Wed, 8 Jan 2025 17:26:55 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip="2604:1380:45d1:ec00::3" ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1736317615; cv=none; b=H/E1xfl9tZCjLvXIfm5rWNcIetMUBeTA4eIgEaNXuoIvS5msDmKqEjLY32hmZAY/285QL+0hmkvjxHyq5ICGs+qPYqbX9KFj/9/DyytRc0FVrKVBOhmQ/HAX1Eqkh/0GVI+i60yLW95pithea+X5NydOg4/ATu3V/L9E88fHVFLNVfnpfWsW1DR4+C2qq/KAJCzX0JH+Y3i+CK9PEToBQPCg0PHbwU793Qw3W+uKJ3JNafIEmSPXTBXsjucy0e5hk5TsvfA9VJnStxT7mx5iYaEPQ8pr0r+pX2y9/4NvxqEsL4OgUBfKxnW8zsdGhbCMqJU3H/zvYPn/99i1vg4tSg== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1736317615; c=relaxed/relaxed; bh=/LNvrIzo+npvfznW/iXVwt2s9BNL0jx/BmS8TasxDnA=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=U4sgVKnTODXpi0fXNKYS7f5Ly26NNkmVTUXkNQQaGKmLUnJH/+htCRsDHiAtNjMRsiEW1bMnEpWLa1duAwEdIW5GB9HiQTPqdcslT6/jwyRU7kQJ61o5nApv/lSnQ+rsmYHnbPnByBCdRZnaUar4NqItDmhqcHkFleAN3hURFP31fmLataYT8MXe+RBKZpoBHdLrn1BcjiAh4XON4nNKtMdp5JPcGngO+eJF7q8Y6L5tXqlXFGGJoPDgYuveWabD8d9pSxKPTYxzlE+oITpF1J/EwHhuxA8eNXKmPoU8usHfkS2issYfrMfaFBTt2wGePJxikoSgmnXVisFJjduiew== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org; dkim=pass (1024-bit key; unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=yV3mq70N; dkim-atps=neutral; spf=pass (client-ip=2604:1380:45d1:ec00::3; helo=nyc.source.kernel.org; envelope-from=akpm@linux-foundation.org; receiver=lists.ozlabs.org) smtp.mailfrom=linux-foundation.org Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=yV3mq70N; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux-foundation.org (client-ip=2604:1380:45d1:ec00::3; helo=nyc.source.kernel.org; envelope-from=akpm@linux-foundation.org; receiver=lists.ozlabs.org) Received: from nyc.source.kernel.org (nyc.source.kernel.org [IPv6:2604:1380:45d1:ec00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4YSdHL05CFz300g for ; Wed, 8 Jan 2025 17:26:52 +1100 (AEDT) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 405F4A40443; Wed, 8 Jan 2025 06:24:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75956C4CED0; Wed, 8 Jan 2025 06:26:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1736317605; bh=ictVswVJ4mGv9GZMqt9hcwWRjSa3QIhF5THgyv+dfIc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=yV3mq70NowsKzsNN4Ez+jnFDFJRIlhbNscdaUiVTLxZRecRmCbvgybiz9uRsrgg0n PjP3lsjSFoN3ZHe8QI2pdayWSJuwfonJJuwBr3DLAHViSi3MWsPfptWuWaWljJtEVC tmLb8vkj5Dj4ezW3MMOW7Coe5YQtHTHUai0uWSDo= Date: Tue, 7 Jan 2025 22:26:43 -0800 From: Andrew Morton To: Alistair Popple Cc: dan.j.williams@intel.com, linux-mm@kvack.org, lina@asahilina.net, zhang.lyra@gmail.com, gerald.schaefer@linux.ibm.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, david@redhat.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com Subject: Re: [PATCH v5 00/25] fs/dax: Fix ZONE_DEVICE page reference counts Message-Id: <20250107222643.80d5509219d6b66c15b1b8af@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 7 Jan 2025 14:42:16 +1100 Alistair Popple wrote: > Device and FS DAX pages have always maintained their own page > reference counts without following the normal rules for page reference > counting. In particular pages are considered free when the refcount > hits one rather than zero and refcounts are not added when mapping the > page. > > Tracking this requires special PTE bits (PTE_DEVMAP) and a secondary > mechanism for allowing GUP to hold references on the page (see > get_dev_pagemap). However there doesn't seem to be any reason why FS > DAX pages need their own reference counting scheme. > > By treating the refcounts on these pages the same way as normal pages > we can remove a lot of special checks. In particular pXd_trans_huge() > becomes the same as pXd_leaf(), although I haven't made that change > here. It also frees up a valuable SW define PTE bit on architectures > that have devmap PTE bits defined. > > It also almost certainly allows further clean-up of the devmap managed > functions, but I have left that as a future improvment. It also > enables support for compound ZONE_DEVICE pages which is one of my > primary motivators for doing this work. > https://lkml.kernel.org/r/wysuus23bqmjtwkfu3zutqtmkse3ki3erf45x32yezlrl24qto@xlqt7qducyld made me expect merge/build/runtime issues, however this series merges and builds OK on mm-unstable. Did something change? What's the story here? Oh well, it built so I'll ship it!