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From: Christoph Hellwig <hch@infradead.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	"Darrick J. Wong" <djwong@kernel.org>,
	Jane Chu <jane.chu@oracle.com>,
	Vishal L Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	"Weiny, Ira" <ira.weiny@intel.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
	Linux NVDIMM <nvdimm@lists.linux.dev>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 0/3] dax: clear poison on the fly along pwrite
Date: Fri, 17 Sep 2021 13:53:33 +0100	[thread overview]
Message-ID: <YUSPzVG0ulHdLWn7@infradead.org> (raw)
In-Reply-To: <CAPcyv4g_qPBER2W+OhCf29kw-+tjs++TsTiRGWgX3trv11+28A@mail.gmail.com>

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.

  reply	other threads:[~2021-09-17 12:57 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14 23:31 [PATCH 0/3] dax: clear poison on the fly along pwrite Jane Chu
2021-09-14 23:31 ` [PATCH 1/3] dax: introduce dax_operation dax_clear_poison Jane Chu
2021-11-04 17:53   ` Christoph Hellwig
2021-09-14 23:31 ` [PATCH 2/3] dax: introduce dax_clear_poison to dax pwrite operation Jane Chu
2021-11-04 17:53   ` Christoph Hellwig
2021-09-14 23:31 ` [PATCH 2/3] dax: introduce dax clear poison to page aligned " Jane Chu
2021-09-14 23:31 ` [PATCH 3/3] libnvdimm/pmem: Provide pmem_dax_clear_poison for dax operation Jane Chu
2021-11-04 17:55   ` Christoph Hellwig
2021-11-04 20:27     ` Jane Chu
2021-09-15  4:44 ` [PATCH 0/3] dax: clear poison on the fly along pwrite Dan Williams
2021-09-15  7:22   ` Jane Chu
2021-09-15 16:15     ` Darrick J. Wong
2021-09-15 20:27       ` Dan Williams
2021-09-16  0:05         ` Darrick J. Wong
2021-09-16  7:11         ` Christoph Hellwig
2021-09-16 18:40           ` Dan Williams
2021-09-17 12:53             ` Christoph Hellwig [this message]
2021-09-17 15:27               ` Darrick J. Wong
2021-09-17 20:21                 ` Dan Williams
2021-09-18  0:07                   ` Darrick J. Wong
2021-09-17 19:37               ` Dan Williams
2021-09-23 20:48         ` Jane Chu
2021-09-23 20:55       ` Jane Chu
2021-09-23 21:42         ` Dan Williams

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