From: "Kani, Toshi" <toshi.kani@hpe.com>
To: "hch@infradead.org" <hch@infradead.org>,
"snitzer@redhat.com" <snitzer@redhat.com>
Cc: "jack@suse.cz" <jack@suse.cz>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"chengnt@lenovo.com" <chengnt@lenovo.com>,
"david@fromorbit.com" <david@fromorbit.com>,
"colyli@suse.de" <colyli@suse.de>,
"dm-devel@redhat.com" <dm-devel@redhat.com>,
"mpatocka@redhat.com" <mpatocka@redhat.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: Snapshot target and DAX-capable devices
Date: Wed, 12 Dec 2018 19:49:25 +0000 [thread overview]
Message-ID: <cdeadbe0b16244a07f2417902c1f46eb1141d96f.camel@hpe.com> (raw)
In-Reply-To: <20181212175047.GA24962@redhat.com>
On Wed, 2018-12-12 at 12:50 -0500, Mike Snitzer wrote:
> On Wed, Dec 12 2018 at 11:12am -0500,
> Christoph Hellwig <hch@infradead.org> wrote:
>
> > Does it really make sense to enhance dm-snapshot? I thought all serious
> > users of snapshots had moved on to dm-thinp?
>
> There are cases where dm-snapshot is still useful for people. But those
> are very niche users. I'm not opposed to others proposing enhancements
> for dm-snapshot in general but it is definitely not a priority (Google's
> dm-bow is an example of a case where dm-snapshot may get extended to
> fulfill google's needs).
>
> But for this specific DAX case, I can only assume efforts to prop up
> dm-snapshot like this are born out of legacy use-cases. The reality is
> getting DAX to work with dm-snapshot is pretty involved (due to mmap,
> etc). This thread got into a lot of the details:
> https://www.redhat.com/archives/dm-devel/2018-August/msg00211.html
>
> So any new attempt to reintroduce DAX support to dm-snapshot (or any
> more complex DM target) will have a very high bar. One that requires
> much more extensive mm and block (interlock) prep work to make DAX
> safe.
Just to be clear, "reintroduce DAX support to dm-snapshot" is a bit
misleading because there wasn't such attempt before. My original
hack/change in dm-snapshot was to support non-DAX use-cases to work with
DAX-capable devices.
Thanks,
-Toshi
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next prev parent reply other threads:[~2018-12-12 19:49 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-27 16:07 Snapshot target and DAX-capable devices Jan Kara
2018-08-27 16:43 ` Kani, Toshi
2018-08-28 7:50 ` Jan Kara
2018-08-28 17:56 ` Mike Snitzer
2018-08-28 22:38 ` Kani, Toshi
2018-08-30 9:30 ` Jan Kara
2018-08-30 18:49 ` Mike Snitzer
2018-08-30 19:32 ` Jeff Moyer
2018-08-30 19:47 ` Mikulas Patocka
2018-08-30 19:53 ` Jeff Moyer
2018-08-30 23:38 ` Dave Chinner
2018-08-31 9:42 ` Jan Kara
2018-09-05 1:25 ` Dave Chinner
2018-12-12 16:11 ` Huaisheng Ye
2018-12-12 16:12 ` Christoph Hellwig
2018-12-12 17:50 ` Mike Snitzer
2018-12-12 19:49 ` Kani, Toshi [this message]
2018-12-12 21:15 ` Theodore Y. Ts'o
2018-12-12 22:43 ` Mike Snitzer
2018-12-14 4:11 ` [dm-devel] " Theodore Y. Ts'o
2018-12-14 8:24 ` [External] " Huaisheng HS1 Ye
2018-12-18 19:49 ` Mike Snitzer
2018-08-30 19:44 ` Mikulas Patocka
2018-08-31 10:01 ` Jan Kara
2018-08-30 22:55 ` Dave Chinner
2018-08-31 9:54 ` Jan Kara
2018-08-30 19:17 ` [dm-devel] " Jeff Moyer
2018-08-31 9:14 ` Jan Kara
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