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From: Dan Williams <dan.j.williams@intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: "y-goto@fujitsu.com" <y-goto@fujitsu.com>,
	"jack@suse.cz" <jack@suse.cz>,
	"fnstml-iaas@cn.fujitsu.com" <fnstml-iaas@cn.fujitsu.com>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	"darrick.wong@oracle.com" <darrick.wong@oracle.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"ruansy.fnst@fujitsu.com" <ruansy.fnst@fujitsu.com>,
	"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"ocfs2-devel@oss.oracle.com" <ocfs2-devel@oss.oracle.com>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"qi.fuli@fujitsu.com" <qi.fuli@fujitsu.com>,
	"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: [Ocfs2-devel] Question about the "EXPERIMENTAL" tag for dax in XFS
Date: Mon, 1 Mar 2021 19:33:28 -0800	[thread overview]
Message-ID: <CAPcyv4ja8gnTR1E-Ge5etm+y69cHwdWN6Bg79wPPF4M=C-w79A@mail.gmail.com> (raw)
In-Reply-To: <20210302024227.GH4662@dread.disaster.area>

On Mon, Mar 1, 2021 at 6:42 PM Dave Chinner <david@fromorbit.com> wrote:
[..]
> We do not need a DAX specific mechanism to tell us "DAX device
> gone", we need a generic block device interface that tells us "range
> of block device is gone".

This is the crux of the disagreement. The block_device is going away
*and* the dax_device is going away. The dax_device removal implies one
set of actions (direct accessed pfns invalid) the block device removal
implies another (block layer sector access offline). corrupted_range
is blurring the notification for 2 different failure domains. Look at
the nascent idea to mount a filesystem on dax sans a block device.
Look at the existing plumbing for DM to map dax_operations through a
device stack. Look at the pushback Ruan got for adding a new
block_device operation for corrupted_range().

> The reason that the block device is gone is irrelevant to the
> filesystem. The type of block device is also irrelevant. If the
> filesystem isn't using DAX (e.g. dax=never mount option) even when
> it is on a DAX capable device, then it just doesn't care about
> invalidating DAX mappings because it has none. But it still may care
> about shutting down the filesystem because the block device is gone.

Sure, let's have a discussion about a block_device gone notification,
and a dax_device gone notification.

> This is why we need to communicate what error occurred, not what
> action a device driver thinks needs to be taken.

The driver is only an event producer in this model, whatever the
consumer does at the other end is not its concern. There may be a
generic consumer and a filesystem specific consumer.

> The error is
> important to the filesystem, the action might be completely
> irrelevant. And, as we know now, shutdown on DAX enable filesystems
> needs to imply DAX mapping invalidation in all cases, not just when
> the device disappears from under the filesystem.

Sure.

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  reply	other threads:[~2021-03-02  3:33 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-26  0:20 [Ocfs2-devel] [PATCH v2 00/10] fsdax, xfs: Add reflink&dedupe support for fsdax Shiyang Ruan
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 01/10] fsdax: Factor helpers to simplify dax fault code Shiyang Ruan
2021-03-03  9:13   ` Christoph Hellwig
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 02/10] fsdax: Factor helper: dax_fault_actor() Shiyang Ruan
2021-03-03  9:28   ` Christoph Hellwig
2021-03-12  9:01     ` ruansy.fnst
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 03/10] fsdax: Output address in dax_iomap_pfn() and rename it Shiyang Ruan
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 05/10] fsdax: Replace mmap entry in case of CoW Shiyang Ruan
2021-03-03  9:30   ` Christoph Hellwig
2021-03-03  9:41     ` ruansy.fnst
2021-03-03  9:44       ` Christoph Hellwig
2021-03-03  9:48   ` Christoph Hellwig
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 08/10] fsdax: Dedup file range to use a compare function Shiyang Ruan
2021-02-26  8:28   ` Shiyang Ruan
2021-03-03  8:20   ` Joe Perches
2021-03-03  8:45     ` ruansy.fnst
2021-03-03  9:04       ` Joe Perches
2021-03-03  9:39       ` hch
2021-03-03  9:46         ` ruansy.fnst
2021-03-04  5:42   ` [Ocfs2-devel] [RESEND PATCH v2.1 " Shiyang Ruan
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 09/10] fs/xfs: Handle CoW for fsdax write() path Shiyang Ruan
2021-03-03  9:43   ` Christoph Hellwig
2021-03-03  9:57     ` ruansy.fnst
2021-03-03 10:43       ` Christoph Hellwig
2021-03-04  1:35         ` ruansy.fnst
2021-02-26  0:20 ` [Ocfs2-devel] [PATCH v2 10/10] fs/xfs: Add dedupe support for fsdax Shiyang Ruan
2021-02-26  9:45 ` [Ocfs2-devel] Question about the "EXPERIMENTAL" tag for dax in XFS ruansy.fnst
2021-02-26 19:04   ` Darrick J. Wong
2021-02-26 19:24     ` Dan Williams
2021-02-26 20:51       ` Dave Chinner
2021-02-26 20:59         ` Dan Williams
2021-02-26 21:27           ` Dave Chinner
2021-02-26 22:41             ` Dan Williams
2021-02-27 22:36               ` Dave Chinner
2021-02-27 23:40                 ` Dan Williams
2021-02-28 22:38                   ` Dave Chinner
2021-03-01 20:55                     ` Dan Williams
2021-03-01 22:46                       ` Dave Chinner
2021-03-02  0:32                         ` Dan Williams
2021-03-02  2:42                           ` Dave Chinner
2021-03-02  3:33                             ` Dan Williams [this message]
2021-03-02  5:38                               ` Dave Chinner
2021-03-02  5:50                                 ` Dan Williams
2021-03-02  3:28                       ` Darrick J. Wong
2021-03-02  5:41                         ` Dan Williams
2021-03-02  7:57                           ` Dave Chinner
2021-03-02 17:49                             ` Dan Williams
2021-03-04 23:40                               ` Darrick J. Wong
2021-03-01  7:26       ` Yasunori Goto
2021-03-01 21:34         ` Dan Williams
     [not found] ` <20210226002030.653855-5-ruansy.fnst@fujitsu.com>
2021-03-03  9:29   ` [Ocfs2-devel] [PATCH v2 04/10] fsdax: Introduce dax_iomap_cow_copy() Christoph Hellwig
     [not found] ` <20210226002030.653855-7-ruansy.fnst@fujitsu.com>
2021-03-03  9:31   ` [Ocfs2-devel] [PATCH v2 06/10] fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero Christoph Hellwig
     [not found] ` <20210226002030.653855-8-ruansy.fnst@fujitsu.com>
2021-02-26  4:14   ` [Ocfs2-devel] [PATCH v2 07/10] iomap: Introduce iomap_apply2() for operations on two files Darrick J. Wong
2021-02-26  8:11     ` ruansy.fnst
2021-02-26  8:25   ` Shiyang Ruan
2021-03-04  5:41   ` [Ocfs2-devel] [RESEND PATCH v2.1 " Shiyang Ruan
2021-03-11 12:30     ` Christoph Hellwig
2021-03-09  6:36 ` [Ocfs2-devel] [PATCH v2 00/10] fsdax, xfs: Add reflink&dedupe support for fsdax Xiaoguang Wang
2021-03-10  1:32   ` ruansy.fnst
2021-03-09 16:19 ` Goldwyn Rodrigues
2021-03-10  1:26   ` ruansy.fnst
2021-03-10 12:30 ` Neal Gompa
2021-03-10 13:02   ` Matthew Wilcox
2021-03-10 13:36     ` Neal Gompa
2021-03-10 13:55       ` Matthew Wilcox
2021-03-10 14:21     ` Goldwyn Rodrigues
2021-03-10 14:26       ` Matthew Wilcox
2021-03-10 17:04         ` Goldwyn Rodrigues
2021-03-11  0:53         ` Dan Williams
2021-03-11  8:26           ` Neal Gompa
2021-03-13 13:07         ` Adam Borowski
2021-03-13 16:24           ` Neal Gompa
2021-03-13 22:00             ` Adam Borowski

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