From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f177.google.com (mail-pg1-f177.google.com [209.85.215.177]) (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 2DFA83FC3 for ; Fri, 17 Sep 2021 19:38:03 +0000 (UTC) Received: by mail-pg1-f177.google.com with SMTP id h3so10568507pgb.7 for ; Fri, 17 Sep 2021 12:38:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=o2+Hh3F66cL6BpjONlixjboMa3d3Dr6Wccaac4ba0jE=; b=vPVoybXUpHkOIx/4oBHOyHOxXIaG88Kxkxe2gf1MN6vplcSMHfkPomSPpz+YdV5+I2 m7oyFT5ixFaermZpqd88wRx43KQtE4XNw/VnDn7EfXhYdZgcFGaWdsuEznvwEOfYW8ab n+YxXRB6lmhJ431BOxOoQE8wCsczglL1XfDT+XX1SbvMDI6omSXbO42R6BQNGkNNfY3w 0IjSq7dNz5H/nNJDKkROUb7wUrC9/QVcJ+KQCl+ZSQAJh2UUET/dM29VdewqTAoVSknq b/ItlBAGc5tpvPvwEpRz4mlw9G1dZBf9962O/bicmwv3ZlANcXPeW1h6r2d/s9u8A4tw N9Aw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=o2+Hh3F66cL6BpjONlixjboMa3d3Dr6Wccaac4ba0jE=; b=SddJZQJ2wUYGCzqurlJAVOa8I0e6tyPjyhX3lcHzOUF0aLNnY9vqaQp0GwNcNLyAOI vjcLDnISzGU3477514uAPY/ewdSE2hiXSbhKSgNTQ11bNg5PZuGVUGnJcgmLAalOupEB ImMNxE+TS7dhAcXsTbdiDTB7dUKIF7PXmweSmv2l9gzGibDQ96Bvt47i7NcxNx2cQlAN O8/rBnfESfdkl/ZV0LU7sfjiu3MLzXWNxJ/7DBcQ68mHC83Chj0gpwWJmG1OILP2Y7Ns lHRYUb/Ydah8HRuJHKI1+wJ0fSH8ezPS74XhQWwKiUYKrcVaOkG66FpvAG4RC/EpQRVr /MVw== X-Gm-Message-State: AOAM531tuLABLiGVO49BQ8PAu5tpAbr5d/PyHNyNpFGoSYfCjhF3Bi3N uulEkaq4RqUKRWHDxYqCI156pz3Ph7HBuujVq0PF5w== X-Google-Smtp-Source: ABdhPJw9Rph55U9iCJhtxsNCpmwsnCdMb15i9Rn5WefNvzVO816JUbUXWBiompaDXIZ9AAqQQxd1N1iZLl7s73K/osU= X-Received: by 2002:a63:1262:: with SMTP id 34mr11217082pgs.356.1631907482638; Fri, 17 Sep 2021 12:38:02 -0700 (PDT) Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20210914233132.3680546-1-jane.chu@oracle.com> <516ecedc-38b9-1ae3-a784-289a30e5f6df@oracle.com> <20210915161510.GA34830@magnolia> In-Reply-To: From: Dan Williams Date: Fri, 17 Sep 2021 12:37:51 -0700 Message-ID: Subject: Re: [PATCH 0/3] dax: clear poison on the fly along pwrite To: Christoph Hellwig Cc: "Darrick J. Wong" , Jane Chu , Vishal L Verma , Dave Jiang , "Weiny, Ira" , Al Viro , Matthew Wilcox , Jan Kara , Linux NVDIMM , Linux Kernel Mailing List , linux-fsdevel , Shiyang Ruan Content-Type: text/plain; charset="UTF-8" On Fri, Sep 17, 2021 at 5:57 AM Christoph Hellwig wrote: > > On Thu, Sep 16, 2021 at 11:40:28AM -0700, Dan Williams wrote: > > > That was my gut feeling. If everyone feels 100% comfortable with > > > zeroingas the mechanism to clear poisoning I'll cave in. The most > > > important bit is that we do that through a dedicated DAX path instead > > > of abusing the block layer even more. > > > > ...or just rename dax_zero_page_range() to dax_reset_page_range()? > > Where reset == "zero + clear-poison"? > > I'd say that naming is more confusing than overloading zero. Ok, I see Darrick has a better suggestion for the shed color. > > > > I'm really worried about both patartitions on DAX and DM passing through > > > DAX because they deeply bind DAX to the block layer, which is just a bad > > > idea. I think we also need to sort that whole story out before removing > > > the EXPERIMENTAL tags. > > > > I do think it was a mistake to allow for DAX on partitions of a pmemX > > block-device. > > > > DAX-reflink support may be the opportunity to start deprecating that > > support. Only enable DAX-reflink for direct mounting on /dev/pmemX > > without partitions (later add dax-device direct mounting), > > I think we need to fully or almost fully sort this out. > > Here is my bold suggestions: > > 1) drop no drop the EXPERMINTAL on the current block layer overload > at all s/drop no drop/do not drop/? > 2) add direct mounting of the nvdimm namespaces ASAP. Because all > the filesystem currently also need the /dev/pmem0 device add a way > to open the block device by the dax_device instead of our current > way of doing the reverse Oh, interesting. I can get on board with that. There's currently no /dev entry for namespaces. It's either /dev/pmemX, or /dev/daxX.Y as a child of /sys/bus/nd/devices/namespaceX.Y. However, I see nothing glaringly wrong with having /dev/daxX.Y always published regardless of whether /dev/pmemX is also present. > 3) deprecate DAX support through block layer mounts with a say 2 year > deprecation period > 4) add DAX remapping devices as needed > > I'll volunteer to write the initial code for 2). And I think we should > not allow DAX+reflink on the block device shim at all. Yeah, I think this can fly.