From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f48.google.com (mail-qv1-f48.google.com [209.85.219.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E31E2F24 for ; Wed, 9 Feb 2022 12:29:58 +0000 (UTC) Received: by mail-qv1-f48.google.com with SMTP id a19so1604991qvm.4 for ; Wed, 09 Feb 2022 04:29:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=JpFYQSMAVe6I09BHQOjAX13imKhzUaXlc2+fdsD9V6E=; b=Z4Eu786ojGcRgS8Eos4sLr66z2Uqqmgi/bDj6/Y33EEsvVWVKeCNJioyDR9vfy9xaY yz3EOxCOZS/4g/fgKsh1/TNwzJVTuJBYxARJaHsw7OoHQBYA7L/O3QtbTl8+Tpf3u32c Go3MoLTkH16938QXNFcpZV2qsCQ+/yOIxJO8+ooqAbmuC9zUdvg0Bg4KHC7DQZrRu5Pr MEV4AdWysZ66pZX4YRzJgy6PJ/mfwT6AapS6FtqHr95tVUvZ/ng6ysJBJp+d6N+bSxfV V5qGUskZ4AiQdRAYVMO4Llk3dzOmsNqH1liuPvseANE5HTBFUWXt5H7TVNAa03BHV8C3 wh9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=JpFYQSMAVe6I09BHQOjAX13imKhzUaXlc2+fdsD9V6E=; b=47UEDf+zFyhDmAZEjxP0YBE2zmZj101vx3XJPveTb3qdVlGsot0kUp3NbtB3JBWUK6 zjSVcYoSgydnTyx5H9e8IQny3hnV+z9Zoq6xXLQtCpzBD7qTOiOdJ9VqU55GfxqTkRqa 0j9BFOY0Pq2NNbBe/KarBoJ93TVJaeuNzXD3eLN5yZKR15yYh/LVETuj2H1bmVNZgfNs apmwbbEvBj4CcqD6u7n1kF0cKXmJG284psFNb5XgGOO45o+lSsx5QAwg7Loo5Dfe9v/I SfloksbvODSnOHSK/IfyhxK7tqmlWDxBBNPoEqPsJn013iNZQy4BYmAhkBwqHzbCqcah XPfg== X-Gm-Message-State: AOAM532OlnzX+NZCvzWb010hxfPMCJLMxA19SQFVAhmb0KSp7Gy/aTFz XycvL5bYPO6tCbEUiWRDrwwmkw== X-Google-Smtp-Source: ABdhPJwf9mdnK2ldlbFJ89Gp7ICZZlJoeyugDA0YNF0idT1dfs12KR4knXDFD3wj+Sh7mIvt9ShqvQ== X-Received: by 2002:a05:6214:21ac:: with SMTP id t12mr1263884qvc.123.1644409797997; Wed, 09 Feb 2022 04:29:57 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-113-129.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.113.129]) by smtp.gmail.com with ESMTPSA id w13sm8052274qkb.106.2022.02.09.04.29.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Feb 2022 04:29:57 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1nHm6e-001DJi-6l; Wed, 09 Feb 2022 08:29:56 -0400 Date: Wed, 9 Feb 2022 08:29:56 -0400 From: Jason Gunthorpe To: Christoph Hellwig Cc: Dan Williams , Andrew Morton , Felix Kuehling , Alex Deucher , Christian =?utf-8?B?S8O2bmln?= , "Pan, Xinhui" , Ben Skeggs , Karol Herbst , Lyude Paul , Alistair Popple , Logan Gunthorpe , Ralph Campbell , Linux Kernel Mailing List , amd-gfx list , Maling list - DRI developers , nouveau@lists.freedesktop.org, Linux NVDIMM , Linux MM Subject: Re: [PATCH 7/8] mm: remove the extra ZONE_DEVICE struct page refcount Message-ID: <20220209122956.GI49147@ziepe.ca> References: <20220207063249.1833066-1-hch@lst.de> <20220207063249.1833066-8-hch@lst.de> <20220209062345.GB7739@lst.de> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220209062345.GB7739@lst.de> On Wed, Feb 09, 2022 at 07:23:45AM +0100, Christoph Hellwig wrote: > On Tue, Feb 08, 2022 at 07:30:11PM -0800, Dan Williams wrote: > > Interesting. I had expected that to really fix the refcount problem > > that fs/dax.c would need to start taking real page references as pages > > were added to a mapping, just like page cache. > > I think we should do that eventually. But I think this series that > just attacks the device private type and extends to the device coherent > and p2p enhacements is a good first step to stop the proliferation of > the one off refcount and to allow to deal with the fsdax pages in another > more focuessed series. It is nice, but the other series are still impacted by the fsdax mess - they still stuff pages into ptes without proper refcounts and have to carry nonsense to dance around this problem. I certainly would be unhappy if the amd driver, for instance, gained the fsdax problem as well and started pushing 4k pages into PMDs. Jason