From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A56BD3FC0 for ; Fri, 17 Sep 2021 12:57:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Um4Uw6AWMgVorPtp96yufuS1WecBa1mqjtkAlbtYeGI=; b=md72ZrUpSFHruswBaqaFU7lRC+ L7wB824poyC9ApIwwu+MCAEK9/02CrbCtyYfP7wUq073ueYVu5gyJQzRUuY2TeAjEBzg2oF+MxikC KUaGfH98tsTnXYxc4mVcNlnK+ysUm9vinJYCMTvnp1AVv24wqCJd1PYfK54jJ/3B6DUARhC1C50Na XR6fNru+F+6dXesMNYqTQ4eZ+utlfAzDg9qbj0fcT4L4GWtQCxEkpMKOcNO1zJkKF5Ib++kPArcYa TIk63kf4QaWOnJ/3O6wFdJT9zaRq962JoainVYKiVPfRPyQPwZqG6ICRASwBj8jcU4jrNLI+c/w1e cP8FJzMQ==; Received: from hch by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mRDMz-000Fp6-Gq; Fri, 17 Sep 2021 12:53:56 +0000 Date: Fri, 17 Sep 2021 13:53:33 +0100 From: Christoph Hellwig To: Dan Williams Cc: Christoph Hellwig , "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 Subject: Re: [PATCH 0/3] dax: clear poison on the fly along pwrite Message-ID: References: <20210914233132.3680546-1-jane.chu@oracle.com> <516ecedc-38b9-1ae3-a784-289a30e5f6df@oracle.com> <20210915161510.GA34830@magnolia> 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: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html 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. > > 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 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 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.