From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Boaz Harrosh <boaz@plexistor.com>,
"Kani, Toshimitsu" <toshi.kani@hp.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux ACPI <linux-acpi@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 14/15] libnvdimm: support read-only btt backing devices
Date: Mon, 22 Jun 2015 17:40:56 +0200 [thread overview]
Message-ID: <20150622154056.GB7952@lst.de> (raw)
In-Reply-To: <CAPcyv4gUp6LtYVuzbQfzq6RbDyf=3nQ0509TPnNCJtVBazrUTg@mail.gmail.com>
On Mon, Jun 22, 2015 at 12:39:34AM -0700, Dan Williams wrote:
> Now I'm confused, you *don't* want the raw device to be hidden *and*
> you want to kill the stacking? Something got crossed. The current
> implementation hides nothing, you get to see the entire stacked
> composition. I'd much prefer to avoid hiding anything.
You see it, but you can't actually use it. The proper way to expose it
would be to the devices visible in the low-level bus sysfs enumeration
logic but only one ULD attach to it.
> The sinister aspect of sector tearing is that most applications don't
> know they have this dependency. At least today's disk's rarely ever
> tear sectors and if they do you almost certainly get a CRC error on
> access. NVDIMMs will always tear and always silently. I think not
> merging BTT at all to see what happens is simply wrong.
So now you leave your users with a choice between a rock and a hard
place, that is using BTT to introduce non-significant overhead and not
supporting DAX or just use it as-is.
--
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next prev parent reply other threads:[~2015-06-22 15:40 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-17 23:54 [PATCH 00/15] libnvdimm: ->rw_bytes(), BLK-mode, unit tests, and misc features Dan Williams
2015-06-17 23:54 ` [PATCH 01/15] block: introduce an ->rw_bytes() block device operation Dan Williams
2015-06-18 19:25 ` Dan Williams
2015-06-17 23:54 ` [PATCH 02/15] libnvdimm: infrastructure for btt devices Dan Williams
2015-06-22 16:34 ` Christoph Hellwig
2015-06-22 16:48 ` Dan Williams
2015-06-22 16:48 ` Christoph Hellwig
2015-06-22 18:32 ` Jeff Moyer
2015-06-22 19:02 ` Dan Williams
2015-06-22 19:09 ` Jeff Moyer
2015-06-23 10:20 ` Christoph Hellwig
2015-06-23 10:19 ` Christoph Hellwig
2015-06-23 15:19 ` Dan Williams
2015-06-23 20:33 ` Dan Williams
2015-06-24 12:10 ` Christoph Hellwig
2015-06-23 10:10 ` Christoph Hellwig
2015-06-17 23:55 ` [PATCH 03/15] nd_btt: atomic sector updates Dan Williams
2015-06-21 10:03 ` Christoph Hellwig
2015-06-21 16:31 ` Dan Williams
2015-06-17 23:55 ` [PATCH 04/15] libnvdimm, nfit, nd_blk: driver for BLK-mode access persistent memory Dan Williams
2015-06-21 10:05 ` Christoph Hellwig
2015-06-21 13:31 ` Dan Williams
2015-06-21 13:56 ` Christoph Hellwig
2015-06-21 14:39 ` Dan Williams
2015-06-17 23:55 ` [PATCH 05/15] tools/testing/nvdimm: libnvdimm unit test infrastructure Dan Williams
2015-06-17 23:55 ` [PATCH 06/15] libnvdimm: Non-Volatile Devices Dan Williams
2015-06-17 23:55 ` [PATCH 07/15] fs/block_dev.c: skip rw_page if bdev has integrity Dan Williams
2015-06-17 23:55 ` [PATCH 08/15] libnvdimm, btt: add support for blk integrity Dan Williams
2015-06-17 23:55 ` [PATCH 09/15] libnvdimm, blk: " Dan Williams
2015-06-17 23:55 ` [PATCH 10/15] libnvdimm: fix up max_hw_sectors Dan Williams
2015-06-21 10:08 ` Christoph Hellwig
2015-06-21 13:28 ` Dan Williams
2015-06-17 23:55 ` [PATCH 11/15] libnvdimm: pmem, blk, and btt make_request cleanups Dan Williams
2015-06-21 10:10 ` Christoph Hellwig
2015-06-21 13:26 ` Dan Williams
2015-06-17 23:55 ` [PATCH 12/15] libnvdimm: enable iostat Dan Williams
2015-06-19 8:34 ` Christoph Hellwig
2015-06-19 9:02 ` Dan Williams
2015-06-21 10:11 ` Christoph Hellwig
2015-06-21 13:22 ` Dan Williams
2015-06-17 23:55 ` [PATCH 13/15] libnvdimm: flag libnvdimm block devices as non-rotational Dan Williams
2015-06-17 23:56 ` [PATCH 14/15] libnvdimm: support read-only btt backing devices Dan Williams
2015-06-18 22:55 ` Vishal Verma
2015-06-21 10:13 ` Christoph Hellwig
2015-06-21 13:21 ` Dan Williams
2015-06-21 13:54 ` Christoph Hellwig
2015-06-21 15:11 ` Dan Williams
2015-06-22 6:30 ` Christoph Hellwig
2015-06-22 7:17 ` Dan Williams
2015-06-22 7:28 ` Christoph Hellwig
2015-06-22 7:39 ` Dan Williams
2015-06-22 15:02 ` Jeff Moyer
2015-06-22 15:41 ` Christoph Hellwig
2015-06-22 16:00 ` Jeff Moyer
2015-06-22 16:32 ` Christoph Hellwig
2015-06-22 16:42 ` Jeff Moyer
2015-06-22 16:48 ` Christoph Hellwig
2015-06-22 18:48 ` Jeff Moyer
2015-06-22 19:04 ` Dan Williams
2015-06-22 19:11 ` Jeff Moyer
2015-06-23 10:10 ` Christoph Hellwig
2015-06-22 15:40 ` Christoph Hellwig [this message]
2015-06-22 16:36 ` Dan Williams
2015-06-22 16:45 ` Christoph Hellwig
2015-06-22 16:54 ` Dan Williams
2015-06-22 16:57 ` Christoph Hellwig
2015-06-22 16:59 ` Dan Williams
2015-06-23 19:30 ` Matthew Wilcox
2015-06-24 12:11 ` Christoph Hellwig
2015-06-17 23:56 ` [PATCH 15/15] libnvdimm, nfit: handle acpi_nfit_memory_map flags Dan Williams
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