From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f171.google.com (mail-pf1-f171.google.com [209.85.210.171]) (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 1787C3FC0 for ; Mon, 23 Aug 2021 20:21:14 +0000 (UTC) Received: by mail-pf1-f171.google.com with SMTP id g14so16356207pfm.1 for ; Mon, 23 Aug 2021 13:21:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=cRgi7oWfHECsTBz/HOJJYyhwTd/oY8CLDyaMGcnc5IA=; b=cT3oI7fsvWd9Kk4N5ASvVpaqvjiKDezL4ogdeKpSwtrBssY3I6QGps+2KtKeN2Sn1J ZLr208u/aGZ/u1b0I1PfHUiaX27fLPbIAEkKCaMlLJOi3qIkpIunPLcW0ObMb/pcC3jD aD+TM+MjjceBfRowI9i1Uwtf7qTY6ds4BXdTKGPvZ/OJlQIF5hT9mjOWdqse/25Hf2Vo IiiuS2tyJ6O5efKMPNzujsYKD7QUG1Ic0XYxqLNI7rzGxaafetGZ6NZ6eCsBAgKe5eyI rUG9ANffxeSUN3oBJ2pViDZgUQM1ufIMBTnGZVWVcg0Z/943ziAhLpK7nfk0cFEY5BhH m7nQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=cRgi7oWfHECsTBz/HOJJYyhwTd/oY8CLDyaMGcnc5IA=; b=HfG00Kf9wNF+QkbfwrUuydUa/zNcO9/FnRuycSyZg+3WJAOI8WL4zflPd0lzCtWh5F eec9ome7xByrNEr6Go8PlT/29T2g7Iz/cXYYsuPRWd0hTky1UH3nkPXdTBVNCkGAJb5o G/jzUImuzKcN3CvQM3VeVQVnkSkVEW4bOm1Og3U5KiJF8vYzXPbwmrRpFQkhiYd1AwRr YoqvKKn1RN4ucxX9brGqnE/8b74P3ysolSwrBpl/2cV9l5u2uWOCNaN4BVvJJkCFNncq AjJHEQmBv2dLl4TFlAZYjojD2y4z1o9ThqflcMLZlEgbCrB6iKl6ibFzOFqum8hu2WLo D4HA== X-Gm-Message-State: AOAM530aYyeoS5UgpNgk/lkLAc3k+XX4gj7pUDOWuo5Olu43FfcHTpbb hX6eYap6RJVoFiq2VvqDo19x/5Yz8awfNeQLJbNgLw== X-Google-Smtp-Source: ABdhPJwo0ftFKtVJku5VlTYKzPAMAn2sKO4dCsEW5FRwAFVeufg7hV8XJ4EkKSmGuFTL4G0VIpsTraKBA0CyHvm5Tjk= X-Received: by 2002:a65:6642:: with SMTP id z2mr21385344pgv.240.1629750073617; Mon, 23 Aug 2021 13:21:13 -0700 (PDT) Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20210820054340.GA28560@lst.de> <20210823160546.0bf243bf@thinkpad> <20210823214708.77979b3f@thinkpad> In-Reply-To: <20210823214708.77979b3f@thinkpad> From: Dan Williams Date: Mon, 23 Aug 2021 13:21:03 -0700 Message-ID: Subject: Re: can we finally kill off CONFIG_FS_DAX_LIMITED To: Gerald Schaefer Cc: Christoph Hellwig , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Linux NVDIMM , linux-s390 Content-Type: text/plain; charset="UTF-8" On Mon, Aug 23, 2021 at 12:47 PM Gerald Schaefer wrote: > > On Mon, 23 Aug 2021 16:05:46 +0200 > Gerald Schaefer wrote: > > > On Fri, 20 Aug 2021 07:43:40 +0200 > > Christoph Hellwig wrote: > > > > > Hi all, > > > > > > looking at the recent ZONE_DEVICE related changes we still have a > > > horrible maze of different code paths. I already suggested to > > > depend on ARCH_HAS_PTE_SPECIAL for ZONE_DEVICE there, which all modern > > Oh, we do have PTE_SPECIAL, actually that took away the last free bit > in the pte. So, if there is a chance that ZONE_DEVICE would depend > on PTE_SPECIAL instead of PTE_DEVMAP, we might be back in the game > and get rid of that CONFIG_FS_DAX_LIMITED. So PTE_DEVMAP is primarily there to coordinate the get_user_pages_fast() path, and even there it's usage can be eliminated in favor of PTE_SPECIAL. I started that effort [1], but need to rebase on new notify_failure infrastructure coming from Ruan [2]. So I think you are not in the critical path until I can get the PTE_DEVMAP requirement out of your way. [1]: https://lore.kernel.org/r/161604050866.1463742.7759521510383551055.stgit@dwillia2-desk3.amr.corp.intel.com [2]: https://lore.kernel.org/r/20210730085245.3069812-1-ruansy.fnst@fujitsu.com