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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 2E7A9E77199 for ; Wed, 8 Jan 2025 06:28:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:Mime-Version:References:In-Reply-To:Message-Id:Subject:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/LNvrIzo+npvfznW/iXVwt2s9BNL0jx/BmS8TasxDnA=; b=MJhuhAHkqSqakumxFUojS2EU47 d6AaMJue1uXV4l89a4jj0nEqfHJXiZmzzWMCdCfqAVoFroF3iA0Jt66o2PBRacuWrZtfmX81iQxbK EFUt9yc4aDV/xV2pDY2B/xmiY1JDdyntXTnGauoPKb3zVlvD6p2pRfB98o0lzXDZbFbrtlYgWRkq8 8YCkShnFv8/HwFIxoaB5lLwGGobkLHTZiJNgDVBueRJw7tYUCCjrUxtKq6fG3NMvoKTLIGa3OByJ8 QWNbAF47M7nBtFypNFGJKHwtkBQDvPTkKw4hJVL2cTcF8gaL6Kaiqm/8npyufsCbcUA7qUPeqhKIF DH8oKRgQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tVPXv-00000007H4J-0ZzI; Wed, 08 Jan 2025 06:28:03 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tVPWh-00000007Gqi-0LOE for linux-arm-kernel@lists.infradead.org; Wed, 08 Jan 2025 06:26:48 +0000 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) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250107_222647_184437_955D5412 X-CRM114-Status: GOOD ( 16.93 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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!